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Ghost voltage, is it real?
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- เผยแพร่เมื่อ 9 ต.ค. 2021
- In this quick little video I run into an uncommon voltage issue while replacing an inducer motor.
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It's often capacitive coupling from adjacent wires, but can also be leakage through control equipment, especially with capacitive filters and snubber networks. You can touch a 240V wire and not get a shock if you're isolated completely from ground, but it's not recommended, as anything that does provide a ground path will result in high current flow through your body.
This is why electricians tend to use test-lamps instead of high impedance meters. The extra load shunts current leakage to give a more accurate indication.
Always listen to professor clive
I was gonna say something , no way you would get hit if you weren't grounded. This guy obviously not an electrician and really nows nothing about electricity if he doesn't now that.
shopping for a test lamp now, as always I appreciate the great wisdom Clive
@@curioushvacguy6876 Are we talking about a neon test light? Haven't seen too many people carrying one of those. Maybe a volt alert pen?
Glad to see you're back!
thanks
I dont ever turn gas off at the actual gas valve anymore. My first heating season, I had to replace 4 because they just wouldn't turn back on.
Good job
@@adamlee3810 I've been there, but it becomes part of the chargeable repair. Today's heating products are becoming problematic here in CA. We've had nothing but problems with these low nox heaters. Garbage and loud. Cheap HSI systems, poorly built circuit boards, gas valves needing an additional appliance regulator. Non adjustable air mixture ports that need adjustments. Company reps are pretty much in the dark on several of these issues. 40 years in the business and they throw us these learning curves that make me feel like I'm back at year one in this trade, but I digress. Lol.
It’s a common phenomenon especially in 12v dc automotive electrical systems. If one strand of a wire is intact on a circuit due to corrosion or other means it’ll still ohm out properly and even have the correct voltage. But try and put a load on the circuit then the voltage will drop to almost nothing and the device will not work. Which is why good mechanics carries a few different size lights and jumpers in his or her toolbox to load test circuits to be 100 percent sure it’s the components or the wiring of the circuit.
That switch is a MMSKG1. It's a motor starting switches that provides manual on/off control of 1/3 phase AC motors where overload protection is not required.
So called, 'ghost voltages' are generally caused by high impedance somewhere in the circuit. Digital meters tend to have a very high input resistance and will show the full voltage because the meter places almost NO load into the circuit. Load the circuit down and the voltage drop across the high impedance will increase to the point where little or no voltage reaches the load. If a tech has a question about this they can connect a lower resistance into the circuit where they wish to measure voltage and will see the voltage drop. It basically comes down to a bad connection somewhere.
That switch that had the problem is a 'motor starter' switch.. It is a more sensitive device sized more precisely to the current draw of a motor than a circuit breaker, and is there to basically continuously monitor the current through the motor. It has a 'heater' precisely sized to the load (motor) and as the current through the motor increases beyond it's rating the heater (usually some kind of bi-metal) heats up will bend and engage a linkage to disconnect the motor. With that type you generally turn the switch all the way off and back on to reset it, or with some, the switch will be off, and only needs to be turned back on. Heaters on a motor contactor generally have a button used to reset them. It would appear that the contacts inside the motor starter switch had some defect or carbon build up creating a point of high impedance (resistance) creating what gets interpreted as a ghost voltage at the load that is detectable when the load is removed, and a high input resistance meter is used to measure the voltage.
I will go on to say that I think the use of a motor starter type switch to feed an entire unit was a misapplication for it's intended use. If you have devices powered by the motor starter switch other than just a motor you're no longer using it for it's intended purpose. They're not meant to feed anything more than a single motor. You'll see them on exhaust fans etc. That' where they belong. Not a unit with power supplies, circuit boards, and other devices that require power as well as one or more motors.
Replacing it with a standard 20 amp switch was the right thing to do. If one wanted to protect the motor inside the unit against overload, then some overload protection device will be mounted inside the unit and supply the motor alone as you'll see in most HVAC applications.
Man thank you for your input , thats very interesting indeed mate 👍 . I briefly heard about ghost voltage before but you made it much clearer so cheers for that mate 🤜🤛
Thanks for the info FRed- very much appreicated sir, this is why I like to stay humble
This is an awesome video and an awesome subject , I've learned a few things from the comment section too .
I think Curious being humble and open to learn opens the door to other techs sharing their knowledge.
Man it's awesome having you back , Bill ! 👍👍👍
thanks Archer, gotta stay humble to learn bro-- my next video is me running a call on a machine im not very familiar with, lots of questions and humility in that one
you'll see that a lot in larger buildings/commercial ran in conduit, bus ducts and chasses that house multiple live conductors. inductive coupling is a pain, at power grid levels it can and will kill you, especially if the coupling occurs from higher primary voltages into parallel or intersecting lines, without any connection the lines could reach a higher potential than the normal voltage.
That type of switch is very common in commercial buildings where you have small motors that have more than one motor on a circuit say you have several small pumps on one 20a circuit but the pumps only use fractional amp draws and one pump fails it will trip the switch for that pump instead of tripping the breaker and shutting down all the pumps so you might have more than one unit heater on that breaker
Nice trick with the “Glow Stick Of Death”! We do Industrial work. On 110v circuits we use the old fashioned Acme Pop Testers. Control circuits will do the same thing. You have what says 110. But no Umph behind it! That’s where the pop tester shines. Thanks for the video. One other thing on the Reznor units. Always check the cabinet ground. If it’s loose or corroded. It will screw up the burner module. Found that more then once! Be well! Best Regards!
The Breaker protects the wire and circuit from shorts and excessive current. The switch was a common isolation and overload switch. This should match the thermal characteristics of the motor and protect it from overload. I am a little surprised to see it on such a small motor, but they do make them for that purpose. Ghost voltages aren't uncommon to see in the Electrical Industry. It is primarily caused by inductive coupling, but there are other causes. The high input impedance of today's digital meters draw so little current that they will show full voltage. That is why I still keep my Wiggy Meter around (Solenoid Voltage Tester) because it puts a load on the wire.. Nice to see you doing Videos again Bill.
Thanks Stewart, imma have to get me one of those wiggys, should have had one long ago
Happy to have you back sir!!
thanks
Nice video Bill! That's a motor protector switch. You pick the amperage you want.
Great video looking forward more of them 👍
keep it coming love your videos just for being honest, thanks alot
Hey Bill , nice to see you out and about ... Good interesting little vid ... Thx ...
Thanks bud
Good one Bill 👍
Hey hey! Great bearded one, nice to see more of ya! Hope all is well and keeps it going stay well Sir!
Hey, thanks!
Great to see you posting great videos again brotha.
Appreciate it
Good find Bill. That was interesting.
Please never ever touch a life wire, especially on a ladder!!
First your ladder might be isolated to the ground by its rubber feet, you might think there is no harm, next thing you might touch a grounded part and your in trouble.
Second electricity through your mussels might drop you down.
Dont wat to se that happen to you.
Like your ch btw. And your approach to problems. And your politeness
Yeah i know I am a crawler. 😄
Greets from the Netherlands.
what about bare handed wiring live standing in waist deep water. better have your full focus on the work!
you make a good point, thats how curiosity killed the cat
the newer meters that have a LO-Z function will help to discern if the reading is true voltage or induced. VFD'S are bad about that . I know having a meter that does everything is now pretty common but I still prefer using my Fluke 116 and if I need to measure amps I have a Fluke 324..
Hell yeah it’s real . Seen it on 480 old WWII spot welder ,spooky.
Been there. Phantom Voltage is the worst for troubleshooting.
The ghost voltage that always got me going was the spark ignition on a range.
Dude i hope you are wearing a safety harness or something. Thats how my dad almost ended in a wheelchair playing with live wires up above a walk in. He still walks like robocop 20 years later no joke...
Interesting issue, and all well explained
Awesome video ! Thanks
Glad you liked it!
I'd never assume a precise 120V floating around to be capacitive coupling, seems like you tested hot to ground and then motor lead to hot but this never actually proved continuity in the circuit. If you're pulling 120VAC hot to ground on a meter and suspect it's ghost voltage then something like a neon lamp would be handy.
your exactly right, something that would actually put a load on the circuit
I was a maintenance supervisor at a big casino in my area. Before I was a maintenance supervisor I worked with my pops doing HVACR with the family business. After that became a mechanical engineer. Many moons later the maintenance supervisor job. We were getting complaints about people getting “shocked” by some of our slot machines. So, with my background I decided to do a feeder study. Turns out there was 142 amps in the ground loop feeding said Casino. Had to reword the 5 xfmrs feeding the place. The backup system and switchgear, everything. Complete with fireworks on the last cut. That was a days work. That’s what you get for going with the lowest bidder and many “value engineering” cuts on an Indian built Casino.
Wow. How did you figure out that problem? So interesting.
Long time no see
Nice find man!
🤘
I was changing a light fixture and the same thing happened. I flipped the breaker and switch off but still picking up ghost voltage. Never figured out why.
@curioushvacguy I'm surprised you didn't see ghost voltage when you were in the appliance field it usually when testing the evap fan next to defrost circuit. If it was more common I would suggest getting the Fluke 116 I believe it has low impedance measurements called loZ
they have a plug in module to deal with "ghost/induced voltage" for all models. other companies likely have them also
nope never saw it in my appliance days, last time I found it was on a exhaust hood-- strange stuff really but a meter upgrade would def help with this, it would make it safer to verify
Well I know I have run into a on and off switch with a technical reset for 120 volt exhaust fans in gables of metal buildings but for heating unit I've never seen that
good, so im not alone then
It go bite yuh....lol
A meter with a lo z function would not have showed that voltage. My Fluke 87 V has that .
For Halloween may a suggest a killer clown costume for you?
Good video.. I would be curious what the voltage would read to ground and neutral while it was connected to the motor.
Good question!
When i hear “hey what’s up guys.” I leave and never watch again.
hahha thats awesome
🤘🤘🤘🤘🤘🤘🤘
That one looked pretty new. The ones I've worked usually looks like hell.
Do a video on wild leg 3 phase systems
I thought I was loosing my mind because of 'ghost' voltage once.
Sounds like two wires are super close to each other but not actually touching. Voltage is induced across the gap similar to a capacitor?
Well dang I just ordered the SC260, maybe I should've ordered the SC480 it has Loz setting🤷 but, really how often do you see this issue? Seems like it's been several years ago when you last had this issue on a exhaust fan on a roof.
exactly, just get an inexpensive little wiggy
I was electrocuted by my chain link fence gate last week. Its attached with wire to a metal pole on the side of my shop. The shop has some kind of metal siding and the poles right up against it. I checked it several times with a that yellow klein pen , a multimeter and by hand and while the gate was open and I touched both the left and right side of the double gates it would shock me. But gates closed it didnt put off voltage. It was about 29v ac. I shut off one breaker at a time and it stopped after I shut the last one off but when I turned everything back on no shocks no voltage ever since?? I'm confused. I'll come back and modify my comment if I figure this out. Also this has never happened before with many years of using the gate.
odd, where you maybe grounded that day and never before?
@@curioushvacguy6876 I usually always try to stay well grounded😄. No everything was the same, didnt do anything differnt that day. Had my shoes on. It's just weird how the fence and shop wall triggerd the test pen and multi meter showed about 29v, and I know what being shocked feels like🤷♂️.. I still haven't figured it out. I'll let you know if I ever do thou.
I’ve seen it a few times in my life, I’ve referred to it as empty voltage but it’s always been a broken wire inside of the insulator or a defective switch. I work on HVAC so not sure what it’s actually called maybe an electrician can fill us in
It's a breaker not a switch, hint, checker the product code.
valid point
Love your commonsense approach to the practical problems
👍
👍👍👍
Oh fun chasing ghost voltage spikes 🙄
👻👻👻 It's a halloween miracle
What was that little orifice you cleaned out, an air balance valve?
Actually that is the port for a tube leading to the air pressure switch- I lost part of the footage showing it wouldnt light because it couldnt close the air switch
Genius. I would’ve replaced the motor like a dumbass.
Long time no see I'm starting to wonder if he cut your beard off LOL
just a quick trim and a tickle thats all
You can have voltage without any problems but that voltage isn’t carrying any amperage, that’s why it hasn’t shocked you.
He was also not grounded :P
I also have mutant abilities
@@curioushvacguy6876
Good to see you back
@@curioushvacguy6876 🤣
Electricians will sometimes work hot wires standing on plywood or something, or use the tingle test with their finger to grab only a hot if they are coupled to the ground just enough, but not enough to complete the circuit painfully. Or wire a receptacle and put on the hot first and save the ground for last so the metal ground body can be held onto during wiring without getting shocked by touching the hot at the same time.
Fiberglass ladder?
Yes,
@@curioushvacguy6876 You won't be grounded on a fiberglass ladder, therefore no circuit will exist whilst standing on the ladder through your feet.
#343 Thumbs uP
i already know how ac electric work
it switch that not making contact with pin it staying closer to it like 2 or 4mm from it and ac voltage is jumping from pin to pin but super lower amp like 0.1 somehow if u ground it will show nothing at all
put wire that closer to ac 120v like 2mm or 4mm I believe you be getting 120v but when touch it ground out
if you dont know much about it go ask electricboom he probably explain it just like voltages jumping from oils to oils same as switch is
Holy shit!!!!
What did I do to deserve this????
What a surprise!!!!