@@EverydayHomeRepairs We in europe don't have any of that we just plug things in and don't care if its reversed or not, we are just careful not to touch any metals, then again if I do touch metal, our whole house has GFCI protection instead of just a few sockets in the kitchen/bathroom
I work as an electrician as well. One of customers gave us an antique light to install but the wires had no indication which was ground, neutral, or hot so ended up pulling my meter out to figure the three wires and hook it up correctly using the ohm setting.
Great explanation on how to use the Klein tester and also the probe. Your example explaining what happens when wires are reversed with a light bulb s an eye-opener! Yikes! Thank you. Much appreciated.
It’s often advantageous to switch the neutral on older fixture. Pilot lights, memory functions and other low voltage functions were allowed to use ground as neutral and worked off the always on hot.
Here we go again. Where were you when I had this problem. I was selling a house and the inspector caught this problem in the bedroom plug. I tried to fix it but without any luck. I called an electrician and he had to trace the problem all the way to the bathroom switch. So the problem could be different than the plug itself. The house was fairly new and I wondered how so many inspectors missed this problem starting with state inspection. Well explained and thank you for sharing
As someone working in residential housing construction as an electrician, it's a horror show. The inspector does not inspect everything. Sometimes my coworkers run out of weather resistant gfi plugs, so they use the normal ones in an effort to fool the inspector, knowing he won't check. Many don't even understand basics and don't utilize critical thinking because they take a completely procedural approach. They don't need to know how everything works they just need to know how to put it together. Everyone comes under the impression that the world has rules that must be followed, but honestly, it seems the are a lot of people in society who just.. don't care. Not out of malice, but pure apathy. Almost reads like exhaustion. And yes, I'm trying desperately to get a new job, it's just really hard.
@@Rin-qj7zt wow. You just described the reality. I have leased a gas station once and few months into the business my A/C started to act up. I called the pros and sure enough he found a cluster of live wire pointing up without caps. He could have easily touched them and hurt himself. The building was almost 2 years old and just disgusting to see violations passed by the inspector. I wish you luck in your future job
Well now that i learned the proper way to find which side is live. I can now confirm there is a lot of wires (outlet) that are wired in reverse in my house 😂 Gotta fix that asap.
@4:38 you speak what happens whit reversed polarity. But it is AC so both wires have voltage, one time negative other time positive. This is special issue in DC applications. Where Hot or positive can arc against metal housing because fuse is before the switch. In the EU where we have dobble voltage, the schuko scoket does not prevent how you power a device. So at the device the power hot (or live how we call it) can be switched. Just by turning the connector in the socket. Special machines or big machines are wired directly. Do not know how the code is in US. but over here we have LIVE is brown Netural is blue and black we use after a switch. So the wire from the breaker is black and goes to the switch. Light bulb have than black and blue wire.
Another thing you did not mention - those ceramic light fixtures are normally hung where? on the ceiling, you may be standing on something, like a chair or a step stool or ladder. I once lived in a house that had that type of fixture in the ceiling of a staircase that led to the basement - I had a ladder propped on the stairs, and me on it when I grabbed the exposed metal box, that was wired incorrectly, it was hot. Guess what happened! I received a jolt and fell off of the improperly erected ladder, and took a tumble down the stairs. Stupid way to prop a ladder, but sometimes, that is what homeowners do. Electric codes are there for a reason. This same house in the winter would sometimes lose one of the phases at the utility pole in the winter, due to weather. That would create some weird conditions due to back feeding through light fixtures and other loads. Turn on a light in the front hall. light in guest bathroom would light but dimly.
I think that would explain how a dad of one of my wife's kindergarten students got killed changing a light bulb. Not sure if it was the shock or the fall from the ladder that killed him though.
Can you show us a good way to fix vaulted ceilings drywall cracking, my split level vaulted ceilings keeps cracking and I fix it and then it cracks more
OK. So years ago I installed a new switch in a table lamp and wasn't sure which side of the cord was neutral. Switch works fine. The outlet and plug are polarized and outlet tests normal with a plug in tester as well as with a DIMM from hot to neutral (120), hot to ground (120) and neutral to ground (0.2). Continuity test reveals that the large end of the plug (neutral) is continuous with the "screw" portion of the socket and the narrow end of the plug (hot) is continuous with the "base" of the lamp socket. When switch is turned off (light off) no voltage from screw portion of bulb to ground but when switch is turned on (light on) there is 120 v from screw portion of bulb to ground. How is this possible? Could a loose neutral wire upstream of outlet cause this?
Good explanation! I think you covered two of the three big topics: outlets, light fixtures, but also switches. If your light fixture is wired correctly, but your switch is wired incorrectly, I think you end up with the same problem. In particular, many people will do fixture work by flipping the switch off because they don't want to deal with the breaker, but if the switch is wired backward, you can still have hot waiting for a path to ground all the way at your work.
I came here to say this. Having a lightbulb with its threads exposed is a good example of something an everyday homeowner (or their kid) might do and not consider it in any way dangerous. But a DIYer trying to change a light fixture with just the switch turned off and not the breaker? That's a nice, educational shock for DIY electrical work. It doesn't matter if you know what you are doing, get a voltage tester or a mulltimeter to check for voltage before you touch ANYTHING. If I don't want to play the breaker guessing game then I will tape the light switch in the off position. That way all of the people I tell not to touch the switch will have a second warning before I come down the ladder and dole out some verbal education.
I am working in a house that was built in 1947. All wires look black. This video prevented me from possibly wiring a new fixture incorrectly tomorrow. So easy to check with just non-contact voltge tester.
if you look closely, one of those wires will have a white or silver stripe on the side, although it may be worn away by now. BTW, if it looks like cloth covered romex and has a light silver glaze on the outside, it's impregnated with arsenic (poison) to keep mice from chewing on it. IOW, wash up after working with it.
@@rupe53 Thank you for the arsenic warning. It is "cloth" covered wiring in conduit on the main floor. Unfortunately, it is in BX behind plaster and it is not feasable to replace.
THANK YOU SO MUCH!!! I struggled to find an explanation as thorough and easy to grasp as this one. I always was taught, heard, and knew it was bad if you reversed polarity, but outside of frying your plugged in device, I never really knew WHY it was bad. This demonstration with the bulbs, the way you showed how you could shock yourself, and the way you explained it, finally has given me the WHY it’s so bad! I’m definitely saving this for future reference.
My dad found most of the outlets were wired in reverse in an older house that we moved into. Being an electrician, he fixed all of those. But I would not have guessed that unscrewing a light bulb would zap you. So now I know.
The Edison screw (which is what you would consider a standard light socket) was developed quite a while ago. The polarized plugs and sockets used today were an attempt to make the Edison screw safer. The intent is for the large easily touched screw portion to be at neutral, while the hot portion is the little contact at the center of the bottom on the socket. (The easy to touch part = neutral, while the hard to touch spot = hot). Frankly, if the Edison screw were to be developed today, it would have been immediately rejected due to safety issues. But given how long ago it was developed, and how many of them have been installed over the years, it's a legacy device that's virtually impossible to get rid of.
@@johncochran8497 you backwards, smaller screw for less current as neautral is a traveler conducter carries 50% of of the curent line , if add both togeatherif current line is 120 v ac and neautral line is 60 v ac = total 180v ac. From ground to neautral is 60 v ac if curent line is being used. The curent line and ground be 120 v ac. Only earth ground is 0 v ac
@@michaelspencer6523 You might want to try again there. Your comment was rather incoherent and wrong. Perhaps you've confused about an Edison Screw vs an Edison Circuit. Even though both use the word "Edison", they are NOT related except in that they're both associated with electricity.
I moved into a home a few years ago that was built in the late 1960s. I didn't realize that several outlets had reversed polarity until I was swapping in some smart plugs. Then, I took my tester around and found the others.
The ceiling fixtures are most dangerous because you are usually on a chair or ladder changing a bulb. Getting zapped may not injure you, but falling off a chair could have very bad outcomes. Old school metal recessed cans are grounded. Even brushing the springs or clips that hold the baffle in place have given me a zap before I finished screwing the bulb in. I'm guessing that was the easiest return when the threads were live neutral was switched off.
My daughter recently bought a house, which was inspected and the inspector found reverse polarity on one of the receptacles, which had a lamp plugged into it. She did not understand why this was unsafe or why it had to be changed. And I explained it much the way you are. Thank you very much.
As always you taught me something today. I have a great respect for electricity and slightly frightened by it. However, you have taught me so many things by your videos, I would rather hang a ceiling fan than put in a new P trap. At least electricity is logical. Thank you🙂
Lol Why is a P trap not logical to you? The water it keeps in it keeps the sewer gases from your septic or sewer system from coming up through your drains. They can be toxic if you smell them over time… Google the issues with drug addicts fermenting their poop and huffing it. Gross, but it shows you why you really wanna block those gases from coming in the house. Plus, it can catch things like rings if you drop them down the drains.
Nice video. All very important facts for anyone doing electrical work and well explained! But a few minor corrections to keep you from spreading false information... At 1:40 you mention: "... plugged in either way and it doesn't matter because they have a little additional circuitry inside that makes them adapt to that.". They don't actually have any such circuitry. With A/C signals as used in power systems, there is no polarity like there is with a DC signal that may need to have wires swapped internally to work correctly. The hot vs neutral has nothing to do with the current flow or power transfer. It's only about human safety. It's all about keeping humans from being shocked. The non-polarized devices keep us safe by having no external metal case or screws that can shock us. With no exposed metal parts and the correct insulation around all circuits, it makes no difference what side internally is connected to hot or neutral. In fact, with no ground reference to work with, the circuit can't even determine which way it's plugged in. At 5:40 you mention: "... or can reduce the life of your device" [when hot and neutral are reversed in a device like a light]. In terms of power and current flow in A/C circuits, it makes no difference if you swap hot and neutral. You are correct that the entire circuit is "hot" RELATIVE to GROUND, so this creates a very dangerous safety issue for sure, but it does not power the device (when the switch is off) any more than with a correctly wired switch. It will not reduce the life of any device. Again, the hot vs neutral polarity is ONLY about human safety. When it is wired incorrectly, we both risk shocking people and starting fires.
I disagree. I have a few machines in my store with rectifiers built into their control boards. Reversing hot an neutral on these machines results in power spikes on shutdown that will fry the micro-controllers. Ask me how I know.
@@johnmiller8884 I can believe you have machines that can be fried by the mistake, but the only way that happens is if the machine is wired wrong internally and uses the safety ground as a conductor of some type. What type of machines are these?
I'm just a homeowner, without a great deal of experience doing home electrical wiring. For example, I knew that reverse polarity in a outlet was bad for the devices, but I didn't know why. And I had no clue about reverse polarity in light sockets. Which makes this a timely video for me, because I have a light socket that is old and I need to replace.
The problem with reversed wiring also applies to re-wiring of table and floor lamps, something an amateur is more likely to attempt - and get confused about.
Absolutely. If you change a damaged cord on a lamp, throw away the old unpolarized plug and use a new polarized one and make sure the wide prong is wired to the socket and not the spring in the center of the socket.
Just a few days ago, I just electrocuted when I placing Lamp for testing.. The hot is the outside of the E27 Cap So I got mad and went to check the person that install the cable.. 😒 But then I realize that I'm the one that install the cable..
@@XanderProduction It could be miswired where the outside wire comes into the fuse or breaker box. If that is the problem, short of having the electric utility come out and pull the meter so you can fix it you are stuck with it. Don't automatically assume you made the mistake. Check it but if it looks correct to you start investigating at the breaker and then where the outside service connects to the main breaker. In Michigan code requiring that the line and neutral be connected "properly" didn't hit the state electrical code until the 2000's.
@@mharris5047 ._.)/ You're correct about the regulation.. But I live in Indonesia.. It's actually me who make the mistake, bcoz I'm the one who check the Live-Neutral but misplaced the connector..
I’ve lived in a variety of houses in different states. I’m always amazed what is not wired correctly. I would recommend a session on aluminum wire and Alcad sockets!
If you have aluminum wiring in your house, have it replaced ASAP! Aluminum wiring just doesn't conduct well enough for use on mains voltage. This is one hell of a fire hazard!!!!!
@@markrobinson8539 Not always. General rule of thumb...yes. An example would be a light fixture like shown in the video but it is 'fed' at the fixture with just a 'switch leg' ran down to the switch. This would see the 'hot' fed down to the switch on one leg and back to the fixture on the other. Not typical in 'new' construction (with free access to open stud bays and the freedom to run what is 'easiest' and needed) but you'd be surprised how often it can be required in rewires or simply just adding a switch to a light that previously was on a pull chain. Code 'allows' for this...so never just assume that black=hot, white=neutral. It may be true more often than not....but it isn't a certainty.
This is why you should hit the breaker before working on a light, if somewhere along the way the polarity was reversed, the switch being off will not help you. I always check and recheck with a dummy stick (hot and neutral) before I go to work. 99.999% of the time it just scares you sometimes it hurts a little bit and it could kill you.
Sometimes a neutral or two from a different circuit might be in a box. It won't set off a non-contact voltage detector, but could give you a serious belt if you separate those "return" conductors.
@@thomaspierce9458 I see that happening, but it would be a perfect storm. also a neutral from a different circuit should be accompanied by a hot from a different circuit, which would be detectable. Once when I was really stupid, I got zapped three times, before I decided I would just hit the main, and avoid a fourth zap.
This was super interesting and valuable to watch around unsafe vs safe connections: more videos comparing safe and unsafe situations around the home would be awesome!
Many a Time when there was no outside receptacle and I couldn't get inside particularly with an older main panel, I would open up and attach a lead of a wire to the hot & another lead to the neutral bus- bar to run a skill saw. I never did make a jumper cord up in such a way I could plug a tester in and see if I had the hot and neutral reversed but I knew it would still work, although it's not 100% safe to do that without verifying that you have the hot and neutral hooked- up correctly.
I recently received my Journeyman license and I can say that this is a great explanation on why the polarity is importantant in the wiring. Thanks for the video.
@@EverydayHomeRepairs any recommendation for testing reverse polarity in light fixtures where there isn't an easily accessible ground? Taking a light fixture down to check wires seems tedious when checking every fixture
@@lumby1412 You can get a polarity plug in tester, like the 3 plug type, and get a test kit from home depot that has alligator test leads, or lightbulb plug on it where you can put them on the "assumed" hot and neutral, and see if it lights up right on the tester.
I had a reverse light bulb socket, I actually found it when I installed an led. I have almost switched all my bulbs to LED, but the fixture in question I noticed a very soft glow when the switch was off, it was such a low amount of output that almost all other light sources had to be off, so I put that led in another fixture and did not have the same symptom. I actually discovered it was backwards at the switch, which meant hot was always hot, but still hopefully that’s useful information to someone
That glow is caused by capacitance between the wires. You can get it even without a reverse switch but that does increase chance of getting it. Better bulbs have methods to prevent that. U just shows how sensitive the bulbs are. A common method of wiring a switch is to draw one cable from a junction box into the switch and use the neutral as the return. The two wires close together create a capacitor that passes some AC.
Interesting. I did not see that coming, but I experienced it with a lamp years ago. I was taking out a lit bulb from a lamp and received a mild shock as I was turning when it turned off. Now I know why.
You should never touch the screw. If the bulb has broke off so that you need to use pliers then use special protection. In case of a plug in lamp unplug.
Actually I never said it was broken, nor was it actually lit. I mis-remembered it which is why I remembered it at all, as pointed out in the video, you should never be shocked by a correctly wired bulb.
Simple rule of thumb... DON'T TOUCH the electrical metal doesn't matter if it turn on or not. Just like even if a gun is unload, you don't point it to anyone's head and pull. Always consider it is live or loaded. Even with the light out I'm a bit concern touching the metal contacts. Never know if there is a cap in there that still storing charge. If i care i would short it out and than touch. But just don't touch is simplest.
Should've also shown, with the hot-neutral reverse before the switch, with the neutral switched off, what should be neutral side remains hot, and, and what should be switched off hot side, also remains hot via any (unenergized) load that's connected ... that was shown on diagram, but should've also shown that with measurements on the circuit ... but looks like your demo circuit didn't match the diagram, as the demo circuit had the hot-neutral reverse after the switch, rather than before. Would also be good to show that those tester light thingies (I oft call them idiot testers ... for ... reason(s)), won't show all possible faults, e.g. hot-neutral reverse + hot ground, and the idiot tester will indicate all is fine - when the situation is even more dangerous than just a hot-ground reverse. Those test lights just show the potential between each pair among what should be hot, neutral, and ground, expecting potential between hot and the other two, but no other potentials. Well, correctly wired isn't the only way to end up with those same relative potential differences among what should be hot, neutral, and ground. That's also why I much prefer the basic two lead neon test light. I can not only test the 3 relative potentials, but I can also test any or all of them between that and a known good ground reference or ... since it's so low current - even myself as crude approximation of ground (similar to screwdrivers with the neon test indicator - but without needing yet another piece of test equipment). If one lead on me and the other to circuit causes it to (barely) light up - it's hot ... if that other lead is on what's supposed to be neutral or ground, somebody messed up the wiring. And yeah, I've seen seriously messed up wiring with hot-neutral reverse + hot ground - hey, it passed the idiot light tester test ... someone probably just rearranged the wires until they saw the light pattern they were expecting, and left it at that. Yeah, traced that sucker back as far as I could ... there was bare copper wire that should'a been ground coming into the apartment unit that was in fact hot - egad ... atop hot-neutral reverse with white wires hot and black at neutral potential ... what a mess.
another note: older homes with knob-&-tube wiring, the neutral is switched, common practice at the time. when replacing a ceiling fixture, turning off the circuit is the best policy. fixtures is the same era with pull-chain & turn knobs, switched the screw shell or neutral.
Years ago I tested the receptacles in the kitchen of a friend's office building. Sure enough one "neutral" was hot. The electrician got there is record time. Thanks. Glad I subscribe.
You also have to be careful with older lamps that have non-polarized plugs. Nothing from before 1962 would be polarized, as outlets weren't required to be polarized. I can't easily find when new lamps were required to have polarized plugs, but I'm sure it was much later. So with plug-in lamps, you should be extra careful and assume the socket is always hot unless it is unplugged. Remember, if the plug is flipped, the switch will be on the neutral, so the shell of the socket will always be live when it's plugged in, even if the light is off.
@@nolanhitchens How else do you control which wire is hot and which is neutral? Especially so that any power switch on the device is on the hot wire, not the neutral wire? Or do they just not care in the EU?
@@pfcrow No idea. I guess things are properly designed and isolated. I've never ever heard of someone being electrocuted while changing a bulb, even with the 230V. And we don't usually cut wires without first taking out the plug or turning off the circuit. I recently cut some wires (insulated pliers) to install a new ceiling light after using the wall switch to turn the light off, assuming (😬) that would also cut the power to the wires. It instantly triggered the (earth leakage?) circuit breaker downstairs. So no harm or damage done, no sparks, nothing. But this video confirms my suspicion that the wall switch may not be connected properly, I will check.
I've seen the neutrals being switched in lighting circuits MANY times, especially in older homes. Never assume that power is interrupted with the switch in the off position; check it with a meter before doing any work.
OR JUST PULL THE FUSE OR BREAKER or do you trust the electrician? The wrongly-wired hot or live light fitting with some low energy bulbs can be enough to cause them to gently glow when switched 'off' and work fine when 'on' !
Great mix of theory and application in these videos. As someone new to this kind of work, it's great not just to learn what to do, but why it works. Thanks!
I think the previous owner of this 1960-era house did much of the wiring himself when it was built. About half of all of the outlets (that were polarized, 2 or 3 prong) had the hot and neutral reversed, and half of the bulbs had the neutral line switched. There were also plenty of the 2 prong non-polarized outlets all over the house.
I was recently installing new wall lanterns on my home when I came across one of the old fixtures wired in reverse. I guess the electrician was left handed because he turned the wire in the other direction. I saw that and wanted to be cautious so I checked with multimeter and found that the wire was still hot after the switch was turned off. Always good to check.
Some older devices - like radios from before 1960 - can be very dangerous with a reversed outlet since the neutral line of the plug was often connected to the chassis. Plug it in backwards (this was before polarized plugs) or into a reversed outlet and the chassis is hot & if you touch a metal part of the case you’ll get a 120V shock.
@@janee7995 Those old electronic devices with tube amplifiers often had the chassis connected to one side of the line, as you correctly said - but not only in the USA. They would be made this way and sold in Canada as well. (I had a few shocks putting the tone-arm on a record.) If tube filaments were in series, this would also happen in other countries with different supply voltages - and no neutral for a return as on the continent of North America.
Those have unpolarized plugs unless modified. I consider those unsafe. period. Note with an unpolarized plug there in principle is no wrong way. It was seen acceptable that the chassis was hot. In Europe they cannot be plugged into grounded sockets as that would be too dangerous if you had a grounded computer next to and there is no legal way besides an isolation transformer to use them.
@@thomaspierce9458 Those were made in most countries. The difference is that in Europe the plug does not fit into grounded sockets so you need to do something really stupid to use them.
believe it or not, kitchen counter appliances were also non polarized back then and everyone had that spiffy looking chrome trim along the counter edge, which could easily ground against the side of the electric stove or the sink. I can't tell you how many times I got a morning wakeup call if I leaned against the counter with a small gap in my bathrobe while making toast! (not what you think because I was shorter then)
I knew about how to wire a socket at one of my jobs where it was a bulb in a metal housing. But we used three wires. Hot, neutral and ground, and the tip of the bottom of the bulb socket was always hot, the black wire, threads neutral the white wire, and green wire was ground and that went to the metal frame parts. About three years ago I was asked to do some lap cord repairs to two lamps. One of the floor lamps had three lights, and neither of these had polarized plugs. Well the three light lamp, was a concern. Two of the sockets were wired one way and the other opposite. This means if a person was to change two bulbs at once while it was plugged in and turned on they would get a shock across their upper body. How dumb was that. I put them all the same way and put on polarized plugs, and made sure the threaded parts were the neutral side of the plug, the wide blade.
if you have reversed wiring then it definatly wasnt inspected before sign off... OR... whoever touched it after passing inspection, for example adding an outlet somewhere, well they had no business touching electrical.. i know homeowners like doing there own work but when it come to electrical JUST DONT!!!! ive seen in person what happens when a home owner touches electrical... long story short ended with 6 victoms...
Well done explanation. This is why you never use a POTATO to unscrew a broken light bulb. Most older homes have the neutral switched and a potato is mostly WATER. Turn the breaker off and use a pair of insulated needle nose pliers to extract the base.
Good advice. I have used potatoes for unscrewing broken light bulbs. Including for a 150 watt high pressure sodium bulb in a yardlight that was busted from being hit with a football during a party. I was depending on the photocell not to kick on, super dangerous because of the high voltage ignitor, (2500 to 4000 volts) found in all high pressure sodium and smaller (150 watt and under) and many newer metal halide fixtures (pulse start metal halide)
If someone theoretically completely scrambled up the wiring so that the ground and neutral wires were actually connected to 120VAC, and connected the hot to ground, the outlet tester and DMM testing would show everything is just fine. This is where a non contact tester would be helpful to identify this odd situation, as that would easily pick it up. If you're up on a ladder and didn't have any known ground reference, the NCV is a good confirmation to have along with the other tools.
This condition actually happens more frequently than you might think. In an old house that was originally wired with 2 wire ungrounded circuits and two prong outlets, sometimes 3 prong outlets are installed without providing a ground wire. In order to fraudulently pass a home inspection and make a 3 light tester indicate correct wiring, a jumper wire is inserted between the neutral and ground screws, aka bootleg ground, or false ground. If there is also reverse polarity, you have a reverse polarity bootleg ground (hot connected to neutral, neutral and ground pins sitting at 120 volts to ground potential) tester will indicate correct wiring, and most if not all appliances will appear to work properly, except a device with metal housing and a three prong plug will have it's case live. And with the possible exception of sensitive electronics, most devices will work without problems, if the polarity is reversed, just not in the safest manner.
I know a lot about wiring. I've known a lot since I was a kid, I've read all the books at the library, I've had the Time Life books on basic wiring, and I went to trade school as a backup plan to learn the more advanced things. Every single house my parents or myself have ever purchased, the wiring was exactly wrong, or a downright fire hazard, except for the house my Mother had built for her. Old wiring, aluminum and copper spliced together without thermal paste, improper wire nuts and in a surprisingly lots of instances, mostly in basements with ceilings, open air splices of bare copper wires twisted together and exposed. This latest house I purchased the idiot put in grounding outlets that didn't have a grounded box nor wire, Used plastic boxes, so they couldn't even be accidentally grounded, Junction boxes spliced into chains of boxes, 4 and 5 times over. Two or more Romex cables haring one clamp strain relief. In one case, no clamp at all. No GFCI in kitchen nor on Washer machine circuits. Just a nightmare that's going to cost me over $20,000.00 to fix. I wish people that don't know what in the hell they're doing would leave their hands off wiring. That's how houses burn down.
In some countries like Finland there is a standard on the wiring. The live hole is on the right but it is a minor error not worth fixing if it is reverse.
I have recently watched lots of your videos, and they are informative. I am a beginner in DIY projects and want to learn more about how to do more DIY. Thank you.
Here's an example, it's raining outside, the kids can't go out and play, so they are bouncing around the house all day long, therefore reducing the life of mom! 😂
I remember back in the early sixties, wall sockets were usually ungrounded although polarized, however, the plugs were neither grounded nor polarized (two prongs, both the same width).
That light bulb example was excellent. I replaced a vanity light above a bathroom sink at an old cabin a few years back and it was not clear which wires were hot or neutral and I didn't have any testing equipment handy. I guess I had a 50/50 chance. Your test was perfect.
there is alot of old houses that switched the neutral and light or outlet would have it constant hot . very bad situation and bite you hard . when going to replace and see switch is off . a shocking way to find out .lol
And in some older houses notably old farm houses with an outbuilding , a yardlight in the middle, and a pair of three way switches, one in the house and the other in the outbuilding, which also contains receptacles which remain live at all times, using only three wires between house and outbuilding, excluding the equipment grounding conductor. How they accomplished that was by hooking the hot and neutral to the travellers on each three way switch, which continues the circuit to the outbuilding. Then a single wire would come off the common of each three way to the yardlight. The bulb will be OFF if it sees two hots or two neutrals, but turns ON when it gets a hot and a neutral, polarity can be correct or reversed depending on the position of the switches.
I ran into something similar here, except the light fixture was hot...so when I went to change the bulb in the basement, the metal light fixture was wired up by someone who didn't know what they were doing and they wired up the neutral and hot backwards, and the threads hit the metal fixture as I was removing the bulb and my finger must've been touching on the top of the thread where the glass meets metal and shocked the hell out of me. Yeah that got rewired real quick. Some people don't need to be touching electricity
Another thing that you need to look out for is when the switch is beyond the fixture. Ex: Power comes into a ceiling light fixture. The hot lead (black) should be connected to the black lead going to the switch and not to the black lead going to the ceiling lamp. The neutral (white) coming back from the switch is now the hot and should be marked (usually a wrap of black electrical tape) and attached to the gold colored terminal or black lead of the fixture. The neutral (white) of the power supply cable is then connected to the silver colored terminal or the white lead from the fixture. Many DIYers get this messed up.
In Europe it is normal to have table lamps. floor standing lamps, etc. with Edison screw lamp holders and fitted with two pin reversible plugs. Therefore a 50/50 chance of reversed polarity. Always a good plan to pull the plug first!
Great job showing how to test the outlet with a tester. But it’s also possible to use the same tester to test a light socket. You just need a few more pieces to connect as follows: Mount an outlet in a box and add two male cords. One cord is polarized two pin and connects to the outlet at hot and neutral. The other cord is three pin and ONLY connects to outlet ground. Then plug outlet tester into outlet. Plug a polarized light socket to outlet adapter into the light being tested. Connect this whole device up using the two pin cord to the light socket and the three pin cord to a known good grounded outlet. The outlet tester will report if the light socket is reverse polarity. I’ve done this test at many houses and most older houses have reverse polarity lights. My own house built in 2004 has half the lights wired wrong. And that’s by a professional electrician and passed inspection.
or in a house that is new enough to have a grounding conductor, plug a grounded extension cord into a known good receptacle, and use a continuity tester to check between the ground pin of the extension cord and the screw shell of lampholders. or hold a non contact voltage tester to the screw shell.
An additional comment --- when checking voltages with a DMM, always reference to a known ground. Some may assume that they can check voltage using the Neutral as the reference but this could lead to incorrect readings with AC voltages if another fixture in the circuit is incorrectly wired. Also check BOTH Hot and Neutral during the same test.
Back in the late 1970’s I worked for a power company. On rare occasions I would find in old Victorian homes wall sconces wired using the old gas light gas line as a neutral. The electric light fixture would have a hot wire connected and a neutral/ground connected from the fixture to the gas line, which was still pressurized. When I asked old timer co-worker about this he told me that at the time it was thought electric lights were a passing fad and would not last. It was cheaper and easier to run a single wire and the gas line was capped and left in the wall so the gas lights could be re-installed. Talk about unsafe!
When you're outdoors it is easy to inadvertently come into contact with the ground. When you do then you're electrically grounded. We use a ground reference for safety but the fact that we do creates a local hazard. Basically if you have to mess with electricity outdoors be careful and try to wear insulative footwear. You do not want to be in the return path for current.
The most common issue I've run into (multiple times), is the light switch itself is wired wrong! So the switch cuts the neutral line and not the power. So the light socket(s) still have live power to them with the switch OFF! I can't tell you how many times I've discovered this problems in the homes I've owned. So I'm extra careful around light switches when replacing bulbs. And some people I've talked to don't understand the problem "It's not on, so its OK". Argh
Man thank you so much for your video. In 10 minutes I learned more than I had learned and understand about wiring issues 😅. I’m definitely subscribing!! Thanks again
Yeah. I definitely have something wrong with my wiring. Every time I turn on my kitchen light, the dining room chandelier flickers even with the dimmer switch turned off
1. reversing the wires can be bad for in old tube radios where often the neutral wire is supposed to be connected to the metal case for grounding but even if the cord has been upgraded to make the radio safer having reversed wiring in the outlet can now liven up the body of the radio. 2. lamp kits there are lamp kits so you can turn a ceramic statue into a lamp by installing a lamp rod nuts and washers and a lamp holder. you can also get replacement lamp holders with switches built in. often if the paper tube that goes between the outer shell and the threaded part of the bulb holder can go missing or degrade to the point where the bulb holder could contact the metal shell and make the threaded base live if wired wrong. so when building a lamp make sure to know what wires are what a good lamp cord should have some marker on the wire to indicate the neutral. when replacing a lamp socket make sure to wire in the replacement properly or there could be safety problems.
@ejonesss I knew that one of the first reasons for polarized plugs was to prevent energizing a metal lamp base. I never knew how that could happen. You mentioned the paper tube that used to be used in old lamps. Thanks for pointing out the card board was the "insulation". Yes, I can totally see how if that paper got compromised it would energize the base. I guess back then paper was easier to use than plastic. Thanks for answering a question that has been long in my head!
5:52 What you want is that the hot side is cut off at the switch. Imagine someone wants to change the light fixture, he might just turn the switch off assuming that will cut power to the socket so he can just take off the fixture and put up a new one. But in this scenario the socket is still hot because the way light is turned off is by taking neutral away from hot. Now someone might touch hot and ground and has quite some surprise.
I've found just one appliance that would not work correctly with reversed polarity: A gas furnace. It uses flame detector based on ion conductivity to ground which does not work when you reverse polarity.
Use the ground connection in the light fixture where the bare copper wire or the green insulated wire is connected. Assuming the light is mounted to a metal junction box and the metal junction box is properly grounded. the metal box is the ground. Of course if the neutral and hot are reversed it's also possible that the JB isn't properly grounded.
Something very important to note about basic plug-in outlet testers: if the outlet is not grounded, they cannot detect reverse polarity. I learned this when my parents bought an old house and asked me to look over the wiring since I’m handy with that sort of thing, and many of the outlets appeared to be ungrounded but otherwise okay to the outlet tester, but when I used a three-prong cord plugged into a known good outlet as a ground reference, over half the outlets in the house were not only ungrounded, but the polarity was reversed as well.
It's amazing what you find in older houses. I have no problem with DIY work, I do it all the time myself, but do your homework and take the time to make sure it's right if you're going to. As my father used to say "if it's worth doing at all, it's worth doing right". I am in an older house, not that old but old enough for the kind of house it is and every 10 minute project turns in to so much more because someone did something wrong to begin with. I'm also a perfectionest so even if it's a minor thing, if I let it go it will annoy me until I go back and fix it.
This is se of the most dangerous advice I've seen! DO NOT DIY YOUR OWN ELECTRIC IF YOU ARE NOT A ELECTRICIAN! DO NOT TEST OUTLETS WITH THE BOX AS NEUTRAL! he didn't even bother to say don't touch the box. This is horrible horrible horrible advice. DONT TOUCH YOUR GOD DAMN ELECTRIC!
I'm not debating that incorrect wiring isn't safe (mostly to you), but how can incorrect wiring damage a product over time? First of all, we've got to acknowledge that AC constantly reverses polarity. I can't really see how "polarity" matters to a device when using AC. Actually, what we call polarity isn't polarity. We just use it to conveniently refer to a hot/neutral system. If we used a hot/hot system, it wouldn't matter which side is which. In fact it may have been that way until 240 came into our homes. When the hot/neutral system became available, people were still using non-polarized lamps and receptacles. Fun times. Basically, zappies do bad things to people, so we started polarizing stuff. As for leaving a hot connected to a device while not in circuit, it's not in circuit so no power is going through it. I'm overlooking zombie power in poorly designed light bulbs for now that are lighting due to capacitance which is in the millivolts. The innards of the device may be idly sitting at the hot voltage potential, but everything sits idly at a voltage. That's why it took thousands of years to even realize it was electricity was even there. People got zapped on doorknobs during the winter, and probably thought it was demons or something.
European Schuko plugs are not polarized and everything works. One of my floor lamps vibrates with AC hum if the switch interrupts the neutral. I can feel this if I slide my fingers across its surface. This way you can sense vibrations that you can't by firmly grasping the appliance. You'd have to go out of your way to touch the lightbulb screw. Modern plastic sockets don't directly connect the screw anymore, and only provide a tab at the bottom. A danger might come if you react and cause a ceiling lamp to fall down and break, or yourself falling down from a ladder.
5:50 That it might reduce the life of equipment when wired reversed is BS.... As long as there is no closed circuit, there's no load or work done by device.. In Europe we do not even have polarized outlets... And you are telling me our equipment is massively having (maybe) a shorter live? 🤣 🤣 🤣 🤣 🤣 🤣 Wouldn't that also mean that the switch has a hard time when polarity is correct? 🤣 IT IS (COULD) ONLY (BE) A SAFETY ISSUE
Thank you for this information. I was just recently replacing a burnt out lamp fixture & this information is going to help me from burning it out again. Again, thank you very much.
I purchased a rehabbed house over a year ago and I just found out that the receptacle for the garbage disposal was wired backwards between HOT & NEUTRAL and I found this out with my Fluke ST120 socket tester. For the longest time, the circuit breaker/GFCI would periodically trip and I do believe I just found out why this was happening because of reverse wiring of the garbage disposal receptacle... THANK you so much for these videos.
I have come across both a reverse-polarity receptacle and a reverse-polarity light fixture, both on the laundry room lighting circuit (receptacle powers fluorescent fixture). Fortunately, both of these issues have been fixed, and the switch is on the hot side.
If TH-cam videos could be rated five stars this would be a genuine 5 star video. Simple, to the point with well explained examples of how to tell if the wiring in your house is suspect. I totally expect your subscriptions to increase if you keep this up!
Best timed video. Exactly what I have been wondering since the weekend when I changed out a 3 way switch. I did not know which was hot and which was not. Thankyou!
Hi again, Second question. I just installed two new ceiling light fixtures (no fans attached) and now have a problem. The wall switches are not turning the lamps off. Sadly, I did not test the lights at the switch plate after installing so I don't know if both of the switches have burned out, or if the builder reversed the polarity. Could I trying connecting the light fixture's Black wire to the unused Red wire in the ceiling? I have seen that the Red wire is for supplemental power. BIG THANKS AGAIN!
Good tutorial.. I'm aussie and live in Thailand. When our house was built, we had the electrics done by an "alleged" electrician. Bahahahaha.. After numerous storms and exploded or dead devices, I decided to check things. I purchased a multi-meter and a power point tester. 3 zones of power points, amounting to 30+ power points, all reversed. I then decided to test light switches (30+), first to ensure correctly wired, but secondly, if the switch or light socket was reversed too. Yup, light switches off and 230v, when lights on, zero volts.. So armed with enough torches, into the roof I go. OMG.. Given the Thai heat, it was long and slow. I checked every junction box and light fitting (35+). Some wiring was correctly wired at the switch or power point, but mostly, each junction box was incorrectly wired from one box to the next too. Thailand gets cable from USA, China, UK and locally manufactured. With that, 4 different colour codes and all made up the wiring in my house. I tried to get the local Thai electricity agency to come around and fix it but all they wanted to do was rip it all out and start again. They however couldn't tell us when they could do it, as Thailand don't usually have qualified electricians for domestic settings. So painstakingly, I went around checking, identifying wiring for every switch, junction box, light, fan fitting and power point. I averaged about 3 junction boxes a day given the extreme heat in the ceiling and the requirement to have household power completely off throughout, given I wasn't trusting of any work previously done. We're all good now. No more explosions or device failure due to electrical issues within the house. I'm alive to tell the tale too, so I must've done something right. Whilst I'm not a qualified electrician by western standards, I am confident now, my house is wired correctly. I know as much if not more than the average Thai person who claims to be a domestic electrician.
This is why BC(common here) to ES adaptors are banned in new zealand (Bayonet cap to edison screw), as they could be installed in a BC fitting either way around(have reported a few for sale, and got sellers spoken too, and possibly fined) Also travel adaptors are banned here, for same reason. Recently got a chinese led light, which had a (illegal) travel adaptor, which was giving me shocks. Turned out body of light was alive at 115vac when turned on , with adaptor one way around, and at 200+vac when switch was off with plug other way around, and shock current was 40ma. Supplier withdrew product when show tests. (we use 230vac @50hz).
Best description of this problem that I have seen to date. Very clear and concise, easy for the layperson to understand. 👍
Thanks John 👍
I completely agree with @john jones
What a great video !
@@EverydayHomeRepairs We in europe don't have any of that we just plug things in and don't care if its reversed or not, we are just careful not to touch any metals, then again if I do touch metal, our whole house has GFCI protection instead of just a few sockets in the kitchen/bathroom
@@BartvandeMosselaar Bad idea. What if the GFI is faulty? The job should be done right or not at all.
I work as an electrician as well. One of customers gave us an antique light to install but the wires had no indication which was ground, neutral, or hot so ended up pulling my meter out to figure the three wires and hook it up correctly using the ohm setting.
Great explanation on how to use the Klein tester and also the probe.
Your example explaining what happens when wires are reversed with a light bulb s an eye-opener! Yikes!
Thank you. Much appreciated.
It’s often advantageous to switch the neutral on older fixture. Pilot lights, memory functions and other low voltage functions were allowed to use ground as neutral and worked off the always on hot.
Here we go again. Where were you when I had this problem. I was selling a house and the inspector caught this problem in the bedroom plug. I tried to fix it but without any luck. I called an electrician and he had to trace the problem all the way to the bathroom switch. So the problem could be different than the plug itself. The house was fairly new and I wondered how so many inspectors missed this problem starting with state inspection. Well explained and thank you for sharing
Good point Hassan and thanks for the example. I think many are caught off guard on what inspectors do and don’t find during the inspection 😁
As someone working in residential housing construction as an electrician, it's a horror show. The inspector does not inspect everything. Sometimes my coworkers run out of weather resistant gfi plugs, so they use the normal ones in an effort to fool the inspector, knowing he won't check. Many don't even understand basics and don't utilize critical thinking because they take a completely procedural approach. They don't need to know how everything works they just need to know how to put it together.
Everyone comes under the impression that the world has rules that must be followed, but honestly, it seems the are a lot of people in society who just.. don't care. Not out of malice, but pure apathy. Almost reads like exhaustion.
And yes, I'm trying desperately to get a new job, it's just really hard.
@@Rin-qj7zt wow. You just described the reality. I have leased a gas station once and few months into the business my A/C started to act up. I called the pros and sure enough he found a cluster of live wire pointing up without caps. He could have easily touched them and hurt himself. The building was almost 2 years old and just disgusting to see violations passed by the inspector. I wish you luck in your future job
One of the dangers of connecting a run of receptacles in series. One gets wired backwards and now everything downstream is backwards.
@@hassanbazzi3545 Before blasting the inspector, is it possible that the previous owner left you this mess?
Well now that i learned the proper way to find which side is live. I can now confirm there is a lot of wires (outlet) that are wired in reverse in my house 😂 Gotta fix that asap.
Great Video, its always good to hit the basics sometimes.
@4:38 you speak what happens whit reversed polarity. But it is AC so both wires have voltage, one time negative other time positive.
This is special issue in DC applications. Where Hot or positive can arc against metal housing because fuse is before the switch.
In the EU where we have dobble voltage, the schuko scoket does not prevent how you power a device. So at the device the power hot (or live how we call it) can be switched. Just by turning the connector in the socket. Special machines or big machines are wired directly.
Do not know how the code is in US. but over here we have LIVE is brown Netural is blue and black we use after a switch.
So the wire from the breaker is black and goes to the switch.
Light bulb have than black and blue wire.
The neutral is grounded so it has no voltage - ever. The phase has voltage referenced to the ground and it alternates between positive and negative.
Awesome video and clear explanation!
Another thing you did not mention - those ceramic light fixtures are normally hung where? on the ceiling, you may be standing on something, like a chair or a step stool or ladder. I once lived in a house that had that type of fixture in the ceiling of a staircase that led to the basement - I had a ladder propped on the stairs, and me on it when I grabbed the exposed metal box, that was wired incorrectly, it was hot. Guess what happened! I received a jolt and fell off of the improperly erected ladder, and took a tumble down the stairs. Stupid way to prop a ladder, but sometimes, that is what homeowners do. Electric codes are there for a reason.
This same house in the winter would sometimes lose one of the phases at the utility pole in the winter, due to weather. That would create some weird conditions due to back feeding through light fixtures and other loads. Turn on a light in the front hall. light in guest bathroom would light but dimly.
I think that would explain how a dad of one of my wife's kindergarten students got killed changing a light bulb. Not sure if it was the shock or the fall from the ladder that killed him though.
Can you show us a good way to fix vaulted ceilings drywall cracking, my split level vaulted ceilings keeps cracking and I fix it and then it cracks more
Well, the light socket polarity is a good idea but it cannot be accomplished if it is connected to a 3-way set of switches.
Thanks!
Nice setup and demo!
Old house some outlets read weird 40v instead of 114, what could be the cause?
OK. So years ago I installed a new switch in a table lamp and wasn't sure which side of the cord was neutral. Switch works fine. The outlet and plug are polarized and outlet tests normal with a plug in tester as well as with a DIMM from hot to neutral (120), hot to ground (120) and neutral to ground (0.2). Continuity test reveals that the large end of the plug (neutral) is continuous with the "screw" portion of the socket and the narrow end of the plug (hot) is continuous with the "base" of the lamp socket. When switch is turned off (light off) no voltage from screw portion of bulb to ground but when switch is turned on (light on) there is 120 v from screw portion of bulb to ground. How is this possible? Could a loose neutral wire upstream of outlet cause this?
Very good video.
Goood explanation!
Great info..!
Thanks!
Just wondering if a LED bulb will iWork if it is reversed. My guess is no
I was a bit skeptical but the LED bulbs I tried worked the same.
Good explanation! I think you covered two of the three big topics: outlets, light fixtures, but also switches. If your light fixture is wired correctly, but your switch is wired incorrectly, I think you end up with the same problem. In particular, many people will do fixture work by flipping the switch off because they don't want to deal with the breaker, but if the switch is wired backward, you can still have hot waiting for a path to ground all the way at your work.
I came here to say this. Having a lightbulb with its threads exposed is a good example of something an everyday homeowner (or their kid) might do and not consider it in any way dangerous. But a DIYer trying to change a light fixture with just the switch turned off and not the breaker? That's a nice, educational shock for DIY electrical work. It doesn't matter if you know what you are doing, get a voltage tester or a mulltimeter to check for voltage before you touch ANYTHING.
If I don't want to play the breaker guessing game then I will tape the light switch in the off position. That way all of the people I tell not to touch the switch will have a second warning before I come down the ladder and dole out some verbal education.
@@docferringer
If I don’t want to play the breaker guessing game?
That’s equal to…
“If you’re willing to run the risk of a shock…”
It's difficult to wire the switch backwards because the black hot wire is the only one attached to the switch and the neutral white wire bypasses it.
We need to go back to wireless lamps and tech like it was before 1800 during the time of the giants
Knob and tube was better
I am working in a house that was built in 1947. All wires look black. This video prevented me from possibly wiring a new fixture incorrectly tomorrow. So easy to check with just non-contact voltge tester.
if you look closely, one of those wires will have a white or silver stripe on the side, although it may be worn away by now. BTW, if it looks like cloth covered romex and has a light silver glaze on the outside, it's impregnated with arsenic (poison) to keep mice from chewing on it. IOW, wash up after working with it.
@@rupe53 Thank you for the arsenic warning. It is "cloth" covered wiring in conduit on the main floor. Unfortunately, it is in BX behind plaster and it is not feasable to replace.
@@rogerhodges7656 ... my home was from 1910 so already have experience with wiring behind plaster. It wasn't fun, but that was 40 years ago.
THANK YOU SO MUCH!!! I struggled to find an explanation as thorough and easy to grasp as this one. I always was taught, heard, and knew it was bad if you reversed polarity, but outside of frying your plugged in device, I never really knew WHY it was bad. This demonstration with the bulbs, the way you showed how you could shock yourself, and the way you explained it, finally has given me the WHY it’s so bad!
I’m definitely saving this for future reference.
My dad found most of the outlets were wired in reverse in an older house that we moved into. Being an electrician, he fixed all of those. But I would not have guessed that unscrewing a light bulb would zap you. So now I know.
I have found the same problem in apartments I moved into, presumably wired by "professional" electricians.
The Edison screw (which is what you would consider a standard light socket) was developed quite a while ago. The polarized plugs and sockets used today were an attempt to make the Edison screw safer. The intent is for the large easily touched screw portion to be at neutral, while the hot portion is the little contact at the center of the bottom on the socket. (The easy to touch part = neutral, while the hard to touch spot = hot). Frankly, if the Edison screw were to be developed today, it would have been immediately rejected due to safety issues. But given how long ago it was developed, and how many of them have been installed over the years, it's a legacy device that's virtually impossible to get rid of.
@@johncochran8497 British use a bayonet mount that has two contacts on the bottom.
@@johncochran8497 you backwards, smaller screw for less current as neautral is a traveler conducter carries 50% of of the curent line , if add both togeatherif current line is 120 v ac and neautral line is 60 v ac = total 180v ac. From ground to neautral is 60 v ac if curent line is being used. The curent line and ground be 120 v ac. Only earth ground is 0 v ac
@@michaelspencer6523 You might want to try again there. Your comment was rather incoherent and wrong.
Perhaps you've confused about an Edison Screw vs an Edison Circuit. Even though both use the word "Edison", they are NOT related except in that they're both associated with electricity.
I moved into a home a few years ago that was built in the late 1960s. I didn't realize that several outlets had reversed polarity until I was swapping in some smart plugs. Then, I took my tester around and found the others.
The electrical code probably didn't specify back then.
@@mharris5047 they are all grounded plugs with the wider neutral at least. It is definitely odd. It was built in 68-69.
@@CarnivoreRonin Same experience here - oddly, nearly exactly half of the outlets and the switches had the hot/neutral swap issue.
The ceiling fixtures are most dangerous because you are usually on a chair or ladder changing a bulb. Getting zapped may not injure you, but falling off a chair could have very bad outcomes.
Old school metal recessed cans are grounded. Even brushing the springs or clips that hold the baffle in place have given me a zap before I finished screwing the bulb in. I'm guessing that was the easiest return when the threads were live neutral was switched off.
My daughter recently bought a house, which was inspected and the inspector found reverse polarity on one of the receptacles, which had a lamp plugged into it. She did not understand why this was unsafe or why it had to be changed. And I explained it much the way you are. Thank you very much.
You bet, thanks for the feedback 👍
Exactly. I've seen older metal lamps where a reverse polarity can electrify the entire lamp.
As always you taught me something today. I have a great respect for electricity and slightly frightened by it. However, you have taught me so many things by your videos, I would rather hang a ceiling fan than put in a new P trap. At least electricity is logical. Thank you🙂
Lol Why is a P trap not logical to you? The water it keeps in it keeps the sewer gases from your septic or sewer system from coming up through your drains. They can be toxic if you smell them over time… Google the issues with drug addicts fermenting their poop and huffing it. Gross, but it shows you why you really wanna block those gases from coming in the house.
Plus, it can catch things like rings if you drop them down the drains.
Nice video. All very important facts for anyone doing electrical work and well explained! But a few minor corrections to keep you from spreading false information...
At 1:40 you mention: "... plugged in either way and it doesn't matter because they have a little additional circuitry inside that makes them adapt to that.".
They don't actually have any such circuitry. With A/C signals as used in power systems, there is no polarity like there is with a DC signal that may need to have wires swapped internally to work correctly. The hot vs neutral has nothing to do with the current flow or power transfer. It's only about human safety. It's all about keeping humans from being shocked. The non-polarized devices keep us safe by having no external metal case or screws that can shock us. With no exposed metal parts and the correct insulation around all circuits, it makes no difference what side internally is connected to hot or neutral. In fact, with no ground reference to work with, the circuit can't even determine which way it's plugged in.
At 5:40 you mention: "... or can reduce the life of your device" [when hot and neutral are reversed in a device like a light].
In terms of power and current flow in A/C circuits, it makes no difference if you swap hot and neutral. You are correct that the entire circuit is "hot" RELATIVE to GROUND, so this creates a very dangerous safety issue for sure, but it does not power the device (when the switch is off) any more than with a correctly wired switch. It will not reduce the life of any device. Again, the hot vs neutral polarity is ONLY about human safety. When it is wired incorrectly, we both risk shocking people and starting fires.
I disagree. I have a few machines in my store with rectifiers built into their control boards. Reversing hot an neutral on these machines results in power spikes on shutdown that will fry the micro-controllers. Ask me how I know.
@@johnmiller8884 I can believe you have machines that can be fried by the mistake, but the only way that happens is if the machine is wired wrong internally and uses the safety ground as a conductor of some type. What type of machines are these?
DIYer. Bought an old fixer upper that needs a lot of updating. I want to make sure I get it correct. Thanks for your vids
You bet, best of luck on your projects.
I'm just a homeowner, without a great deal of experience doing home electrical wiring. For example, I knew that reverse polarity in a outlet was bad for the devices, but I didn't know why. And I had no clue about reverse polarity in light sockets.
Which makes this a timely video for me, because I have a light socket that is old and I need to replace.
Best of luck on the light fixture swap 👍
The device does not care. It does not know which side is hot and which not. All it sees is the difference.
The problem with reversed wiring also applies to re-wiring of table and floor lamps, something an amateur is more likely to attempt - and get confused about.
I likely did that with my mother's table lamps when I was a kid.
Absolutely. If you change a damaged cord on a lamp, throw away the old unpolarized plug and use a new polarized one and make sure the wide prong is wired to the socket and not the spring in the center of the socket.
Just a few days ago, I just electrocuted when I placing Lamp for testing.. The hot is the outside of the E27 Cap
So I got mad and went to check the person that install the cable..
😒 But then I realize that I'm the one that install the cable..
@@XanderProduction It could be miswired where the outside wire comes into the fuse or breaker box. If that is the problem, short of having the electric utility come out and pull the meter so you can fix it you are stuck with it. Don't automatically assume you made the mistake. Check it but if it looks correct to you start investigating at the breaker and then where the outside service connects to the main breaker. In Michigan code requiring that the line and neutral be connected "properly" didn't hit the state electrical code until the 2000's.
@@mharris5047 ._.)/ You're correct about the regulation.. But I live in Indonesia..
It's actually me who make the mistake, bcoz I'm the one who check the Live-Neutral but misplaced the connector..
I’ve lived in a variety of houses in different states. I’m always amazed what is not wired correctly. I would recommend a session on aluminum wire and Alcad sockets!
Hey John, thanks for the feedback and those would both make for good videos 👍
@@EverydayHomeRepairs Also would be good to explain what black/ white wires are in Romex. What should be hot, what is neutral.
@@JohnKenIRB233 Black is live (hot) and white is Neutral in the USA
If you have aluminum wiring in your house, have it replaced ASAP! Aluminum wiring just doesn't conduct well enough for use on mains voltage. This is one hell of a fire hazard!!!!!
@@markrobinson8539 Not always. General rule of thumb...yes. An example would be a light fixture like shown in the video but it is 'fed' at the fixture with just a 'switch leg' ran down to the switch. This would see the 'hot' fed down to the switch on one leg and back to the fixture on the other. Not typical in 'new' construction (with free access to open stud bays and the freedom to run what is 'easiest' and needed) but you'd be surprised how often it can be required in rewires or simply just adding a switch to a light that previously was on a pull chain. Code 'allows' for this...so never just assume that black=hot, white=neutral. It may be true more often than not....but it isn't a certainty.
This is why you should hit the breaker before working on a light, if somewhere along the way the polarity was reversed, the switch being off will not help you. I always check and recheck with a dummy stick (hot and neutral) before I go to work. 99.999% of the time it just scares you sometimes it hurts a little bit and it could kill you.
Sometimes a neutral or two from a different circuit might be in a box. It won't set off a non-contact voltage detector, but could give you a serious belt if you separate those "return" conductors.
@@thomaspierce9458 I see that happening, but it would be a perfect storm. also a neutral from a different circuit should be accompanied by a hot from a different circuit, which would be detectable. Once when I was really stupid, I got zapped three times, before I decided I would just hit the main, and avoid a fourth zap.
This was super interesting and valuable to watch around unsafe vs safe connections: more videos comparing safe and unsafe situations around the home would be awesome!
Thanks for the feedback Ryan 👍
Many a Time when there was no outside receptacle and I couldn't get inside particularly with an older main panel, I would open up and attach a lead of a wire to the hot & another lead to the neutral bus- bar to run a skill saw. I never did make a jumper cord up in such a way I could plug a tester in and see if I had the hot and neutral reversed but I knew it would still work, although it's not 100% safe to do that without verifying that you have the hot and neutral hooked- up correctly.
Well done with well thought out demonstration display. Thanks for the time you put in this video.
Happy to help and thanks for the feedback!
I recently received my Journeyman license and I can say that this is a great explanation on why the polarity is importantant in the wiring. Thanks for the video.
Appreciate the feedback Ramon 👍. Best of luck on your career!
@@EverydayHomeRepairs any recommendation for testing reverse polarity in light fixtures where there isn't an easily accessible ground? Taking a light fixture down to check wires seems tedious when checking every fixture
@@lumby1412 You can get a polarity plug in tester, like the 3 plug type, and get a test kit from home depot that has alligator test leads, or lightbulb plug on it where you can put them on the "assumed" hot and neutral, and see if it lights up right on the tester.
I had a reverse light bulb socket, I actually found it when I installed an led. I have almost switched all my bulbs to LED, but the fixture in question I noticed a very soft glow when the switch was off, it was such a low amount of output that almost all other light sources had to be off, so I put that led in another fixture and did not have the same symptom. I actually discovered it was backwards at the switch, which meant hot was always hot, but still hopefully that’s useful information to someone
That glow is caused by capacitance between the wires. You can get it even without a reverse switch but that does increase chance of getting it. Better bulbs have methods to prevent that. U just shows how sensitive the bulbs are.
A common method of wiring a switch is to draw one cable from a junction box into the switch and use the neutral as the return. The two wires close together create a capacitor that passes some AC.
Interesting. I did not see that coming, but I experienced it with a lamp years ago. I was taking out a lit bulb from a lamp and received a mild shock as I was turning when it turned off. Now I know why.
There ya go 👍
You should never touch the screw. If the bulb has broke off so that you need to use pliers then use special protection. In case of a plug in lamp unplug.
Potatoes!
Actually I never said it was broken, nor was it actually lit. I mis-remembered it which is why I remembered it at all, as pointed out in the video, you should never be shocked by a correctly wired bulb.
1 second ago
Your surprise, could be a DEADLY SHOCK. which is no surprise. Please do not spoon feed the panzy terms
Simple rule of thumb... DON'T TOUCH the electrical metal doesn't matter if it turn on or not. Just like even if a gun is unload, you don't point it to anyone's head and pull. Always consider it is live or loaded.
Even with the light out I'm a bit concern touching the metal contacts. Never know if there is a cap in there that still storing charge. If i care i would short it out and than touch. But just don't touch is simplest.
Should've also shown, with the hot-neutral reverse before the switch, with the neutral switched off, what should be neutral side remains hot, and, and what should be switched off hot side, also remains hot via any (unenergized) load that's connected ... that was shown on diagram, but should've also shown that with measurements on the circuit ... but looks like your demo circuit didn't match the diagram, as the demo circuit had the hot-neutral reverse after the switch, rather than before.
Would also be good to show that those tester light thingies (I oft call them idiot testers ... for ... reason(s)), won't show all possible faults, e.g. hot-neutral reverse + hot ground, and the idiot tester will indicate all is fine - when the situation is even more dangerous than just a hot-ground reverse. Those test lights just show the potential between each pair among what should be hot, neutral, and ground, expecting potential between hot and the other two, but no other potentials. Well, correctly wired isn't the only way to end up with those same relative potential differences among what should be hot, neutral, and ground. That's also why I much prefer the basic two lead neon test light. I can not only test the 3 relative potentials, but I can also test any or all of them between that and a known good ground reference or ... since it's so low current - even myself as crude approximation of ground (similar to screwdrivers with the neon test indicator - but without needing yet another piece of test equipment). If one lead on me and the other to circuit causes it to (barely) light up - it's hot ... if that other lead is on what's supposed to be neutral or ground, somebody messed up the wiring. And yeah, I've seen seriously messed up wiring with hot-neutral reverse + hot ground - hey, it passed the idiot light tester test ... someone probably just rearranged the wires until they saw the light pattern they were expecting, and left it at that. Yeah, traced that sucker back as far as I could ... there was bare copper wire that should'a been ground coming into the apartment unit that was in fact hot - egad ... atop hot-neutral reverse with white wires hot and black at neutral potential ... what a mess.
another note: older homes with knob-&-tube wiring, the neutral is switched, common practice at the time. when replacing a ceiling fixture, turning off the circuit is the best policy. fixtures is the same era with pull-chain & turn knobs, switched the screw shell or neutral.
Years ago I tested the receptacles in the kitchen of a friend's office building. Sure enough one "neutral" was hot. The electrician got there is record time. Thanks. Glad I subscribe.
Thanks for sharing
You also have to be careful with older lamps that have non-polarized plugs. Nothing from before 1962 would be polarized, as outlets weren't required to be polarized. I can't easily find when new lamps were required to have polarized plugs, but I'm sure it was much later. So with plug-in lamps, you should be extra careful and assume the socket is always hot unless it is unplugged. Remember, if the plug is flipped, the switch will be on the neutral, so the shell of the socket will always be live when it's plugged in, even if the light is off.
Being from the EU I had never even heard of polarized plugs and outlets before I saw them on TH-cam. What a strange concept..🤔
@@nolanhitchens How else do you control which wire is hot and which is neutral? Especially so that any power switch on the device is on the hot wire, not the neutral wire? Or do they just not care in the EU?
@@pfcrow No idea. I guess things are properly designed and isolated. I've never ever heard of someone being electrocuted while changing a bulb, even with the 230V. And we don't usually cut wires without first taking out the plug or turning off the circuit.
I recently cut some wires (insulated pliers) to install a new ceiling light after using the wall switch to turn the light off, assuming (😬) that would also cut the power to the wires. It instantly triggered the (earth leakage?) circuit breaker downstairs. So no harm or damage done, no sparks, nothing. But this video confirms my suspicion that the wall switch may not be connected properly, I will check.
I've seen the neutrals being switched in lighting circuits MANY times, especially in older homes. Never assume that power is interrupted with the switch in the off position; check it with a meter before doing any work.
OR JUST PULL THE FUSE OR BREAKER or do you trust the electrician? The wrongly-wired hot or live light fitting with some low energy bulbs can be enough to cause them to gently glow when switched 'off' and work fine when 'on' !
I don't care since I shut off the incoming mains when changing light bulb but I do appreciate your advice on this matter.
Great mix of theory and application in these videos. As someone new to this kind of work, it's great not just to learn what to do, but why it works. Thanks!
I think the previous owner of this 1960-era house did much of the wiring himself when it was built. About half of all of the outlets (that were polarized, 2 or 3 prong) had the hot and neutral reversed, and half of the bulbs had the neutral line switched. There were also plenty of the 2 prong non-polarized outlets all over the house.
I was recently installing new wall lanterns on my home when I came across one of the old fixtures wired in reverse. I guess the electrician was left handed because he turned the wire in the other direction. I saw that and wanted to be cautious so I checked with multimeter and found that the wire was still hot after the switch was turned off. Always good to check.
Some older devices - like radios from before 1960 - can be very dangerous with a reversed outlet since the neutral line of the plug was often connected to the chassis. Plug it in backwards (this was before polarized plugs) or into a reversed outlet and the chassis is hot & if you touch a metal part of the case you’ll get a 120V shock.
Only in usa.
The rest of the world didn't have that issue .
But then usa was and is a 5th world nation
@@janee7995 Those old electronic devices with tube amplifiers often had the chassis connected to one side of the line, as you correctly said - but not only in the USA. They would be made this way and sold in Canada as well. (I had a few shocks putting the tone-arm on a record.) If tube filaments were in series, this would also happen in other countries with different supply voltages - and no neutral for a return as on the continent of North America.
Those have unpolarized plugs unless modified. I consider those unsafe. period. Note with an unpolarized plug there in principle is no wrong way. It was seen acceptable that the chassis was hot.
In Europe they cannot be plugged into grounded sockets as that would be too dangerous if you had a grounded computer next to and there is no legal way besides an isolation transformer to use them.
@@thomaspierce9458 Those were made in most countries. The difference is that in Europe the plug does not fit into grounded sockets so you need to do something really stupid to use them.
believe it or not, kitchen counter appliances were also non polarized back then and everyone had that spiffy looking chrome trim along the counter edge, which could easily ground against the side of the electric stove or the sink. I can't tell you how many times I got a morning wakeup call if I leaned against the counter with a small gap in my bathrobe while making toast! (not what you think because I was shorter then)
Always love watching your videos!
Thx!
I knew about how to wire a socket at one of my jobs where it was a bulb in a metal housing. But we used three wires. Hot, neutral and ground, and the tip of the bottom of the bulb socket was always hot, the black wire, threads neutral the white wire, and green wire was ground and that went to the metal frame parts.
About three years ago I was asked to do some lap cord repairs to two lamps. One of the floor lamps had three lights, and neither of these had polarized plugs. Well the three light lamp, was a concern. Two of the sockets were wired one way and the other opposite. This means if a person was to change two bulbs at once while it was plugged in and turned on they would get a shock across their upper body. How dumb was that. I put them all the same way and put on polarized plugs, and made sure the threaded parts were the neutral side of the plug, the wide blade.
if you have reversed wiring then it definatly wasnt inspected before sign off... OR... whoever touched it after passing inspection, for example adding an outlet somewhere, well they had no business touching electrical.. i know homeowners like doing there own work but when it come to electrical JUST DONT!!!! ive seen in person what happens when a home owner touches electrical... long story short ended with 6 victoms...
Amen!! They have no idea, the hazards they are creating!
Well done explanation. This is why you never use a POTATO to unscrew a broken light bulb.
Most older homes have the neutral switched and a potato is mostly WATER.
Turn the breaker off and use a pair of insulated needle nose pliers to extract the base.
Good advice. I have used potatoes for unscrewing broken light bulbs. Including for a 150 watt high pressure sodium bulb in a yardlight that was busted from being hit with a football during a party. I was depending on the photocell not to kick on, super dangerous because of the high voltage ignitor, (2500 to 4000 volts) found in all high pressure sodium and smaller (150 watt and under) and many newer metal halide fixtures (pulse start metal halide)
If someone theoretically completely scrambled up the wiring so that the ground and neutral wires were actually connected to 120VAC, and connected the hot to ground, the outlet tester and DMM testing would show everything is just fine.
This is where a non contact tester would be helpful to identify this odd situation, as that would easily pick it up.
If you're up on a ladder and didn't have any known ground reference, the NCV is a good confirmation to have along with the other tools.
This condition actually happens more frequently than you might think. In an old house that was originally wired with 2 wire ungrounded circuits and two prong outlets, sometimes 3 prong outlets are installed without providing a ground wire. In order to fraudulently pass a home inspection and make a 3 light tester indicate correct wiring, a jumper wire is inserted between the neutral and ground screws, aka bootleg ground, or false ground. If there is also reverse polarity, you have a reverse polarity bootleg ground (hot connected to neutral, neutral and ground pins sitting at 120 volts to ground potential) tester will indicate correct wiring, and most if not all appliances will appear to work properly, except a device with metal housing and a three prong plug will have it's case live. And with the possible exception of sensitive electronics, most devices will work without problems, if the polarity is reversed, just not in the safest manner.
I know a lot about wiring. I've known a lot since I was a kid, I've read all the books at the library, I've had the Time Life books on basic wiring, and I went to trade school as a backup plan to learn the more advanced things. Every single house my parents or myself have ever purchased, the wiring was exactly wrong, or a downright fire hazard, except for the house my Mother had built for her. Old wiring, aluminum and copper spliced together without thermal paste, improper wire nuts and in a surprisingly lots of instances, mostly in basements with ceilings, open air splices of bare copper wires twisted together and exposed.
This latest house I purchased the idiot put in grounding outlets that didn't have a grounded box nor wire, Used plastic boxes, so they couldn't even be accidentally grounded, Junction boxes spliced into chains of boxes, 4 and 5 times over. Two or more Romex cables haring one clamp strain relief. In one case, no clamp at all. No GFCI in kitchen nor on Washer machine circuits. Just a nightmare that's going to cost me over $20,000.00 to fix. I wish people that don't know what in the hell they're doing would leave their hands off wiring. That's how houses burn down.
Why did you buy it then?
@@stevepettersen3283 Because I don't function well being homeless.
Outlet "polarization" is a completely foreign concept to me, in the Netherlands we use shuco sockets and plugs.
All plugs and sockets are reversible.
In some countries like Finland there is a standard on the wiring. The live hole is on the right but it is a minor error not worth fixing if it is reverse.
I have recently watched lots of your videos, and they are informative. I am a beginner in DIY projects and want to learn more about how to do more DIY. Thank you.
You bet, thanks for the support 👍
Around the 2 minute mark, you likely meant to say “transformer” instead of “inverter”. Interesting video, thanks!
There are both inverters and transformers for that use Case
Safety issue on reversed polarity - absolutely. "Reduce life of device"? Can you provide a source for that claim?
Here's an example, it's raining outside, the kids can't go out and play, so they are bouncing around the house all day long, therefore reducing the life of mom! 😂
I remember back in the early sixties, wall sockets were usually ungrounded although polarized, however, the plugs were neither grounded nor polarized (two prongs, both the same width).
That light bulb example was excellent. I replaced a vanity light above a bathroom sink at an old cabin a few years back and it was not clear which wires were hot or neutral and I didn't have any testing equipment handy. I guess I had a 50/50 chance. Your test was perfect.
Thanks for the feedback 👍👍
there is alot of old houses that switched the neutral and light or outlet would have it constant hot . very bad situation and bite you hard . when going to replace and see switch is off . a shocking way to find out .lol
And in some older houses notably old farm houses with an outbuilding , a yardlight in the middle, and a pair of three way switches, one in the house and the other in the outbuilding, which also contains receptacles which remain live at all times, using only three wires between house and outbuilding, excluding the equipment grounding conductor. How they accomplished that was by hooking the hot and neutral to the travellers on each three way switch, which continues the circuit to the outbuilding. Then a single wire would come off the common of each three way to the yardlight. The bulb will be OFF if it sees two hots or two neutrals, but turns ON when it gets a hot and a neutral, polarity can be correct or reversed depending on the position of the switches.
I ran into something similar here, except the light fixture was hot...so when I went to change the bulb in the basement, the metal light fixture was wired up by someone who didn't know what they were doing and they wired up the neutral and hot backwards, and the threads hit the metal fixture as I was removing the bulb and my finger must've been touching on the top of the thread where the glass meets metal and shocked the hell out of me. Yeah that got rewired real quick. Some people don't need to be touching electricity
@Jannie Kirsten did you not read my comment?! I was changing a damn light bulb.
Just bought a tester to check my entire house. Thank you for the well made video.
You bet!
Another thing that you need to look out for is when the switch is beyond the fixture. Ex: Power comes into a ceiling light fixture. The hot lead (black) should be connected to the black lead going to the switch and not to the black lead going to the ceiling lamp. The neutral (white) coming back from the switch is now the hot and should be marked (usually a wrap of black electrical tape) and attached to the gold colored terminal or black lead of the fixture. The neutral (white) of the power supply cable is then connected to the silver colored terminal or the white lead from the fixture. Many DIYers get this messed up.
Hi I am from Australia but I live in Philippines and all the wires are black
That makes things interesting 🤔
In Europe it is normal to have table lamps. floor standing lamps, etc. with Edison screw lamp holders and fitted with two pin reversible plugs. Therefore a 50/50 chance of reversed polarity. Always a good plan to pull the plug first!
Great job showing how to test the outlet with a tester. But it’s also possible to use the same tester to test a light socket. You just need a few more pieces to connect as follows: Mount an outlet in a box and add two male cords. One cord is polarized two pin and connects to the outlet at hot and neutral. The other cord is three pin and ONLY connects to outlet ground. Then plug outlet tester into outlet. Plug a polarized light socket to outlet adapter into the light being tested. Connect this whole device up using the two pin cord to the light socket and the three pin cord to a known good grounded outlet. The outlet tester will report if the light socket is reverse polarity.
I’ve done this test at many houses and most older houses have reverse polarity lights. My own house built in 2004 has half the lights wired wrong. And that’s by a professional electrician and passed inspection.
or in a house that is new enough to have a grounding conductor, plug a grounded extension cord into a known good receptacle, and use a continuity tester to check between the ground pin of the extension cord and the screw shell of lampholders. or hold a non contact voltage tester to the screw shell.
Great demo and visual aids and theory behind the topic. Thank you!!! Good advice on safety as well!!!
An additional comment --- when checking voltages with a DMM, always reference to a known ground. Some may assume that they can check voltage using the Neutral as the reference but this could lead to incorrect readings with AC voltages if another fixture in the circuit is incorrectly wired. Also check BOTH Hot and Neutral during the same test.
Not an issue... As he was only checking if there was ANY considerable voltage... Might read wrong but that is not a problem in this measurement.
If it's an old house there is no ground usually
Back in the late 1970’s I worked for a power company. On rare occasions I would find in old Victorian homes wall sconces wired using the old gas light gas line as a neutral. The electric light fixture would have a hot wire connected and a neutral/ground connected from the fixture to the gas line, which was still pressurized. When I asked old timer co-worker about this he told me that at the time it was thought electric lights were a passing fad and would not last. It was cheaper and easier to run a single wire and the gas line was capped and left in the wall so the gas lights could be re-installed. Talk about unsafe!
Microsoft thought the Internet was just a fad too. Maybe they still do? But yeah sometimes people can be really wrong about some things.
It isn't that bad....don't let those old Victorian homes gaslight you.
I got a tingle one year replacing a burned out C9 Christmas lamp on my outdoor Christmas tree. I was using a pre-polorized string set.
When you're outdoors it is easy to inadvertently come into contact with the ground. When you do then you're electrically grounded. We use a ground reference for safety but the fact that we do creates a local hazard. Basically if you have to mess with electricity outdoors be careful and try to wear insulative footwear. You do not want to be in the return path for current.
The most common issue I've run into (multiple times), is the light switch itself is wired wrong! So the switch cuts the neutral line and not the power. So the light socket(s) still have live power to them with the switch OFF! I can't tell you how many times I've discovered this problems in the homes I've owned. So I'm extra careful around light switches when replacing bulbs. And some people I've talked to don't understand the problem "It's not on, so its OK". Argh
Man thank you so much for your video. In 10 minutes I learned more than I had learned and understand about wiring issues 😅. I’m definitely subscribing!! Thanks again
Yeah. I definitely have something wrong with my wiring. Every time I turn on my kitchen light, the dining room chandelier flickers even with the dimmer switch turned off
1. reversing the wires can be bad for in old tube radios where often the neutral wire is supposed to be connected to the metal case for grounding but even if the cord has been upgraded to make the radio safer having reversed wiring in the outlet can now liven up the body of the radio.
2. lamp kits there are lamp kits so you can turn a ceramic statue into a lamp by installing a lamp rod nuts and washers and a lamp holder.
you can also get replacement lamp holders with switches built in.
often if the paper tube that goes between the outer shell and the threaded part of the bulb holder can go missing or degrade to the point where the bulb holder could contact the metal shell and make the threaded base live if wired wrong.
so when building a lamp make sure to know what wires are what a good lamp cord should have some marker on the wire to indicate the neutral.
when replacing a lamp socket make sure to wire in the replacement properly or there could be safety problems.
@ejonesss I knew that one of the first reasons for polarized plugs was to prevent energizing a metal lamp base. I never knew how that could happen. You mentioned the paper tube that used to be used in old lamps. Thanks for pointing out the card board was the "insulation". Yes, I can totally see how if that paper got compromised it would energize the base. I guess back then paper was easier to use than plastic. Thanks for answering a question that has been long in my head!
Good point about old radios even if it has a new polarized plug attached it offers no protection if the outlet is wired wrong.
5:52 What you want is that the hot side is cut off at the switch. Imagine someone wants to change the light fixture, he might just turn the switch off assuming that will cut power to the socket so he can just take off the fixture and put up a new one. But in this scenario the socket is still hot because the way light is turned off is by taking neutral away from hot. Now someone might touch hot and ground and has quite some surprise.
Well explained. Thank you for posting
You bet!
I've found just one appliance that would not work correctly with reversed polarity: A gas furnace. It uses flame detector based on ion conductivity to ground which does not work when you reverse polarity.
Question: How do I test for reverse polarity in the case of a light fixture. What do I use for ground?
Use the ground connection in the light fixture where the bare copper wire or the green insulated wire is connected. Assuming the light is mounted to a metal junction box and the metal junction box is properly grounded. the metal box is the ground. Of course if the neutral and hot are reversed it's also possible that the JB isn't properly grounded.
@@minuteman4199 they could always give it the lick test. That never fails!
Great content thank you as a DIYer all this extra knowledge helps out a lot and thank you for all the great lessons 👍
Something very important to note about basic plug-in outlet testers: if the outlet is not grounded, they cannot detect reverse polarity. I learned this when my parents bought an old house and asked me to look over the wiring since I’m handy with that sort of thing, and many of the outlets appeared to be ungrounded but otherwise okay to the outlet tester, but when I used a three-prong cord plugged into a known good outlet as a ground reference, over half the outlets in the house were not only ungrounded, but the polarity was reversed as well.
It's amazing what you find in older houses. I have no problem with DIY work, I do it all the time myself, but do your homework and take the time to make sure it's right if you're going to. As my father used to say "if it's worth doing at all, it's worth doing right". I am in an older house, not that old but old enough for the kind of house it is and every 10 minute project turns in to so much more because someone did something wrong to begin with. I'm also a perfectionest so even if it's a minor thing, if I let it go it will annoy me until I go back and fix it.
This is my dilemma in an older house that has no ground I have to figure out how to test for reversed polarity
This is se of the most dangerous advice I've seen! DO NOT DIY YOUR OWN ELECTRIC IF YOU ARE NOT A ELECTRICIAN! DO NOT TEST OUTLETS WITH THE BOX AS NEUTRAL! he didn't even bother to say don't touch the box. This is horrible horrible horrible advice. DONT TOUCH YOUR GOD DAMN ELECTRIC!
Very well explained subject. Thanks for sharing and hopefully saving someone from an accident.
I'm not debating that incorrect wiring isn't safe (mostly to you), but how can incorrect wiring damage a product over time? First of all, we've got to acknowledge that AC constantly reverses polarity. I can't really see how "polarity" matters to a device when using AC. Actually, what we call polarity isn't polarity. We just use it to conveniently refer to a hot/neutral system. If we used a hot/hot system, it wouldn't matter which side is which. In fact it may have been that way until 240 came into our homes. When the hot/neutral system became available, people were still using non-polarized lamps and receptacles. Fun times. Basically, zappies do bad things to people, so we started polarizing stuff. As for leaving a hot connected to a device while not in circuit, it's not in circuit so no power is going through it. I'm overlooking zombie power in poorly designed light bulbs for now that are lighting due to capacitance which is in the millivolts. The innards of the device may be idly sitting at the hot voltage potential, but everything sits idly at a voltage. That's why it took thousands of years to even realize it was electricity was even there. People got zapped on doorknobs during the winter, and probably thought it was demons or something.
European Schuko plugs are not polarized and everything works. One of my floor lamps vibrates with AC hum if the switch interrupts the neutral. I can feel this if I slide my fingers across its surface. This way you can sense vibrations that you can't by firmly grasping the appliance.
You'd have to go out of your way to touch the lightbulb screw. Modern plastic sockets don't directly connect the screw anymore, and only provide a tab at the bottom. A danger might come if you react and cause a ceiling lamp to fall down and break, or yourself falling down from a ladder.
5:50 That it might reduce the life of equipment when wired reversed is BS.... As long as there is no closed circuit, there's no load or work done by device.. In Europe we do not even have polarized outlets... And you are telling me our equipment is massively having (maybe) a shorter live? 🤣 🤣 🤣 🤣 🤣 🤣 Wouldn't that also mean that the switch has a hard time when polarity is correct? 🤣
IT IS (COULD) ONLY (BE) A SAFETY ISSUE
Thank you for this information. I was just recently replacing a burnt out lamp fixture & this information is going to help me from burning it out again. Again, thank you very much.
I purchased a rehabbed house over a year ago and I just found out that the receptacle for the garbage disposal was wired backwards between HOT & NEUTRAL and I found this out with my Fluke ST120 socket tester. For the longest time, the circuit breaker/GFCI would periodically trip and I do believe I just found out why this was happening because of reverse wiring of the garbage disposal receptacle...
THANK you so much for these videos.
I have come across both a reverse-polarity receptacle and a reverse-polarity light fixture, both on the laundry room lighting circuit (receptacle powers fluorescent fixture). Fortunately, both of these issues have been fixed, and the switch is on the hot side.
My favorite video program ....excellent...like to see more plumbing and electrical issues! Keep up the good work....thumbs up!
If TH-cam videos could be rated five stars this would be a genuine 5 star video. Simple, to the point with well explained examples of how to tell if the wiring in your house is suspect. I totally expect your subscriptions to increase if you keep this up!
Best timed video. Exactly what I have been wondering since the weekend when I changed out a 3 way switch. I did not know which was hot and which was not. Thankyou!
Hi again, Second question. I just installed two new ceiling light fixtures (no fans attached) and now have a problem.
The wall switches are not turning the lamps off. Sadly, I did not test the lights at the switch plate after installing
so I don't know if both of the switches have burned out, or if the builder reversed the polarity.
Could I trying connecting the light fixture's Black wire to the unused Red wire in the ceiling? I have seen
that the Red wire is for supplemental power.
BIG THANKS AGAIN!
Good tutorial..
I'm aussie and live in Thailand. When our house was built, we had the electrics done by an "alleged" electrician. Bahahahaha..
After numerous storms and exploded or dead devices, I decided to check things. I purchased a multi-meter and a power point tester.
3 zones of power points, amounting to 30+ power points, all reversed.
I then decided to test light switches (30+), first to ensure correctly wired, but secondly, if the switch or light socket was reversed too.
Yup, light switches off and 230v, when lights on, zero volts..
So armed with enough torches, into the roof I go. OMG..
Given the Thai heat, it was long and slow.
I checked every junction box and light fitting (35+).
Some wiring was correctly wired at the switch or power point, but mostly, each junction box was incorrectly wired from one box to the next too.
Thailand gets cable from USA, China, UK and locally manufactured. With that, 4 different colour codes and all made up the wiring in my house.
I tried to get the local Thai electricity agency to come around and fix it but all they wanted to do was rip it all out and start again. They however couldn't tell us when they could do it, as Thailand don't usually have qualified electricians for domestic settings.
So painstakingly, I went around checking, identifying wiring for every switch, junction box, light, fan fitting and power point.
I averaged about 3 junction boxes a day given the extreme heat in the ceiling and the requirement to have household power completely off throughout, given I wasn't trusting of any work previously done.
We're all good now. No more explosions or device failure due to electrical issues within the house. I'm alive to tell the tale too, so I must've done something right.
Whilst I'm not a qualified electrician by western standards, I am confident now, my house is wired correctly. I know as much if not more than the average Thai person who claims to be a domestic electrician.
This is why BC(common here) to ES adaptors are banned in new zealand (Bayonet cap to edison screw), as they could be installed in a BC fitting either way around(have reported a few for sale, and got sellers spoken too, and possibly fined) Also travel adaptors are banned here, for same reason.
Recently got a chinese led light, which had a (illegal) travel adaptor, which was giving me shocks. Turned out body of light was alive at 115vac when turned on , with adaptor one way around, and at 200+vac when switch was off with plug other way around, and shock current was 40ma. Supplier withdrew product when show tests. (we use 230vac @50hz).