Dustin, this is why I never considered my self an an a electriction. I can bend EMT like an artist but I know better not to trust my skills to pull wire until I have a licensed electriction go over it all. This is a true trade on education of the laws of electrical physics
@@tfun101 Back in the early 1970's completed a 7 step Electrical Apprenticeship in an industrial program and received a Journeyman's Certification. The Apprenticeship program at the time was recognized by the IBEW to be fundamentally equivalent and obtaining the IBEW Journeyman's card was mostly a formality. At he time both the IBEW and the automotive industry were recruiting our guys. I was USWA at the time so we had a pretty good package and plenty of OT available. I was considering making the move but the company offered me a position in electrical management. That included education reimbursement so I could pursue my EE degree. Our apprenticeship had included multiple EE classes at a highly recognized engineering university extension and my credit could carry over allowing a fast track path toward my degree. I chose that option. It was a great opportunity. Sadly these kinds of things don't exist much anymore. I don't regret the decision at all. I as very much a hands-on kind of guy, but realized could accomplish much more in management and ultimately make more money too. The choice got me into some huge projects working with the latest technologies. It was tough though because managing a full time plus job and attending school at night meant I was on the go all the time. I got my degree and continued to advance in the companies management while making a lot of contacts within the industry. Amassed a ton of CE credits ang the way through numerous manufacturer programs. I became a project engineer in a billion dollar joint venture green field project. I spent close to 15 years on the design and build of that project and was then chosen to run all the electrical and instrumentation at that facility. That included hiring and training all of our technicians and developing our own apprenticeship program. At the same time I was very involved in higher levels of corporate management. Then about 20 years ago I took full retirement and quickly joined up with an engineering company doing project engineer and project management, Probably spent 80% of my time in the field. We worked exclusively with IBEW guys. In between some big projects I got involved in doing training of our clients and also for the IBEW. I started making a shift between project management and training. Over time, passed on a lot of big projects as project manager because these are enormous high demand roles and instead did limited consulting on them. I reduced my field work to about 20% and focused more on the engineering management side and building training programs tied to the projects. As I was aging and wanted more free time, I moved more into a consultation role. Project management is very demanding and because oi the pace, it can be a 25/7 job. (Not a typo, but an expression of the demanding role it can be.) Tried to pick smaller projects to consult on. That included some with both commercial and residential contractor companies. That is pretty much where I lost all respect for those doing residential construction. I had never in my entire career come across such unqualified people. And the management folks were even worse than the guys on the job. I pissed off a lot of owners when I told them they were violating laws with their total disregard of OSHA and the NEC code. They even expressed that they did not care at all about this and they got paid for delivering good enough, fast and cheap. I even had one tell me that if they ever got into trouble, they'd just get out of it through bankruptcy and then build a new LLC. They told me that none of their workers had the resources to pursue any legal actions and they would destroy them in court. Absolute worst case was having to buy them off with a few thousand dollars. Almost all these guys said they would not hire IBEW guys because they wanted too much money and were more trouble than they were worth. I saw plenty of examples at several jobsites where these guys operated with the same mentality as the guys managing them. Some of these contractors tried to bid jobs with our engineering company and they were quickly disqualified. I knew the right questions to ask in bidders meetings to where these guys showed themselves as complete idiots. Although it was not a written rule, our engineering company did not do any jobs with non IBEW workers with the exception of a few small companies specializing in IT stuff. Ultimately, I scaled back to where I worked part time for these guys, only consulting on hand picked smallish projects or for specific limited parts of bigger jobs. Then I got offered teaching project for local community college with multiple campuses across the state. We built a program for HS kids tied to one of their technical degree program. Somewhat to my surprise, I was very well received by these kids. All the teaching had done before was with adults. Didn't know how well I would do with today's HS kids. Also sometimes doing custom classes for local companies. most of the college staff were some pretty sharp guys but only had experience in academia. They didn't get rated very high for any of there custom stuff with local companies and I was very well received. I added another dimension they did not have with their traditional staff. Through the years as became more management and more engineer with less hands on, I missed that kind of work. So over time. I built my own shop with capabilities that make a lot of guys jealous. I do some mentoring with promising students and other wise a variety of miscellaneous stuff, including experimenting and creating some of my own stuff. Built some PLC trainers for use in my classes and always looking at making training aids for hands on labs. I also enjoy testing some of the, so called, "latest and greatest" wiring devices. Particularly stuff with questionable claims. And of course, often do a lot of repairs for friends and family. Almost always have some sort of project going that includes both mechanical and electrical skills. I get some of my mentored kids involve in these things. I have in the past been involved in issuing opinions on NEC code changes too. My roots are in industrial and automation, however I'm a strong believer that all the electrical theory applies across all the different sub fields. Part of my low opinion of "installer electricians" is that few have had any real training in the theory of the work they are doing. And guys who will tell me that something doesn't apply to residential wiring. My guess is they often hear about things they do being wrong and they seem to have a distaste for engineers as guys trying to make their jobs harder. Maybe it comes from being shown that they are doing something wrong. But it's something I see in a lot of guys doing residential work including things like concrete and roofing. IDK when it happened, but it used to be that most of these guys had respect for what the engineers told them and that seems rare anymore. IDK, but I think some of this comes from the shady contractors that employ them and some may com from the fact that so manyof these guys were HS dropouts or barely graduated.
Great video Dustin. A few comments. I have done VD calls thousands of times over 35 years. If you have a motor that is 15 amps at 115 volts and have a voltage drop issue, changing the voltage to 230 volts makes a considerable difference. The 15 amps in your calculation drops to 7.5 amps. As a designer, I’m trying to get to the correct conductor size as quickly as possible. Putting cm as denominator gives % volt drop. If you put maximum volts drop you allow as denominator(120x.03=3.6) the answer will be cm. Pick your conductor that is at or larger than the number and you are good to go. When doing lighting loads, like in parking lots, you should not calc full branch circuit load at farthest length. Start at farthest distance and the load at that point. Work your way back to the panel decreasing length and increasing the load. The reason NEC uses 3% & 5% is not only to make sure equipment will work, but that in motor circuits, the breakers can handle the increased amps. I hope you do not mind the comments. Respectfully, Kevin
Voltage Drop Clarification: - Simply, the voltage drop between two points on a conductor always occurs due to resistance in the conductor between those two points: longer the distance, the greater the voltage drop. - The resistance of a conductor is determined by the resistivity coefficient of the conductor’s material and the diameter of the conductor. (Remember, current flows on the outside skin of the conductor., and voltage flows on the inside - simplistic analogy) - In a commercial AC system, multi-phase systems have different "apparent" voltage drop per the same conductor diameter due to the “phase angle” difference - For practical and standard analysis of voltage drop, you have to consider three things (1) material type and size of the conductors, (2) is it a DC or AC single or multi-phase system, and (3) what type of load is at the end of the conductor - purely resistive (i.e., incandescent bulb or heating element) vs. inductive load (i.e., motor, transformer, etc.) - The simplest explanation of what the common cause of voltage drop in residential and commercial wiring systems is due to using too small of a conductor for the type and amount of power consumed in a system
That was so interesting and at the end, I was wondering how much voltage drop is acceptable because 7 volts didn't really seem that big of a deal. Then I did the math and saw that it was about 8% and realized yup, that's why that motor wasn't happy. Thx Dustin for really helping us understand this. Your knowledge and passion for the subject is evident in every video.
That is at 120v. At 240 volts it would be only a 3% drop. But at 12v that 7 volts is a 58% voltage drop. This is one of the big reasons we increase the voltage when we know there will be a voltage drop.
@@ecospider5 Voltage drop does not decrease to 3% at 240 volts. To begin with ANSI sets the national standard for voltage tolerances. There is an A and B range for voltage tolerances at the service entry. Range A is +/- 5%. This allows 5% for the utility and 5% for the customer. As for a motor, there is no such thing as a 240 volt motor. It would be a 230 volt motor that is used on a 240 system and can be utilized from 207 to 253 volts (+/- 10% of nameplate rating) per NEMA standards. These are national standards that are recognized across all industries.
Code aside, how much is acceptable depends on what the load is. Something like a battery charger might not care at all, it will just take a little longer. Lights can be very sensitive. And transferred power is what really matters, and it varies by the square of the voltage. So a small change in voltage may cause a significantly larger change in power.
@@strehlow that is also covered in a code, PST flicker. It is the perception of flicker in an incandescent light the human eye can notice. It is on a curve, the smaller the voltage drop the more events are allowable in a given amount of time.
I don't know who you are, I don't know if you're stupid, or brilliant. Do you know that you have taught me more about electrical work than any other source I have used. I cannot thank you enough. You must just love to teach to do this.
So glad I subscribed. I applied to an electrical union nearby tested, interviewed, got my placement . It’s been a little over a year, I haven’t gotten a call yet but I’m still trying to learn as much as I can and I found this and these videos have been very helpful. Thank you.
I recently went on a cruise ship. They are notorious for having few outlets and you never know which plug type you get. What I want to ask about is that they forbid surge protectors. ?? Where does ground go at sea? Google said they don't deliver 120 hot and neutral but two opposing 60v hots. I know it doesn't pertain to your target audience, but this sounds like a very interesting geek out on topic.
Years ago I helped a guy with a long run of 1,000 ft for a 240 / 120 line. He said, what can I get at the end? Went to the charts for 2/0 aluminum and came up with 50 amps before we had a 5% drop. Turned out to be right on the money when checking with a meter. For those who may argue the numbers, this was a hunk of service cable bought surplus for $1 per foot. It had a #0 neutral so there's our limiting factor when using the 120 volt legs.
I have a question. After you run the wire, if you take a voltage reading. Would it should the voltage drop? Or this is only going to happen when a load is applied?
I'm gonna call BS. 2/0 aluminum at 1000 ft and 50 amps. You will get about a13% V drop, or 104V at the meter. You would need 500 mcm to stay within 5% at 1000'.
@@TnTBLACK95 ... I was going from memory, and that 5% should have been 15%. (my mistake) Now that you mentioned this the goal was to stay above 105 volts. IOW, my draw had to be well under 50 amps. Again, going from memory.... I recall loading one leg at a time and the real numbers for continuous draw were probably in the 40 amp range with something closer to 110 volts. These days the service is used for other things and real draw is under 20 amps a leg. Of course, we also cut the feed short so now just under 800 ft. Since this thread is about how to avoid voltage drop I will mention that one guy thought we could do the run in #6 wire... till we had a little talk about using the charts. Charts are a handy thing to have!
@@rupe53 that makes a lot more sense. lol I'm a power quality tech for the utility company and run into these types of situations regularly. To save money a secondary will be extended to serve a new customer or these old houses are being remodeled with multiple hvac units. Since engineers go by what "their book says" I downloaded a pretty handy app for figuring wire size, load drop, power factor, resistance....
Awesome video. You talking about motor loads brought up another possible video idea. Talk about motor starters and overloads. A/C motors and D/C motors. Soft starts. Motor load conductor sizing … keep up the great work. I look forward to these videos every Monday and Wednesday 👍
I took two semesters of electronic technology…quit because I could NOT understand it…mostly due to the worst teacher I’ve ever had. You have easily made me understand this wizardry easily in twenty minutes. Amazing teaching ability!
Dustin's videos are always so informative and he makes everything so easy to understand. I wish these videos existed when I was an apprentice. This is a good lesson on why you should always take your own measurements.
Thanks for that info. I am in the process of designing a wiring panel to a pond area that is about 250 ft. from the main panel and I was trying to figure out how to estimate the voltage drop over that distance and size my wire correctly. Great content, keep it coming!!!
This video is very reason why I hate most extension cords! Not heavy enough for the distance or the load requirement. Plus, you get situations where people daisy chain the smaller gauge cords.
Hey Dustin, I’m a huge fan, really support what you do. I’m a fellow sparky who does mostly residential. Could you please do a video on fire alarms if you can and explain the different systems. I would really love to learn more
Thanks for your thorough patience for us of the OLDER generation! I've learned tons from you! I used to say I knew enough to be dangerous. Now I understand why that was a true statement! Thanks for making me a safer person! You da man! Steve
very good topic. I was waiting for you to address voltage drop due to weak connection: wire nut error, wrong torque on a buss bar, etc. That said, focusing on proper conductor size & type over a specific distance - very useful and valuable vid. Thank you for doing that. A+
I truly appreciate and love how well you explain things even to the person who already understands it already. Thank you kindly and greatly appreciate you and your Chanel!
Cable length and faults Can be accurately be measured with a, TDR "Time domain reflectometers" In the IT industry, cable TV and radio systems We can accurately locate faults and determine exact lengths of conductors. Have a spool of wire want to know how long it is, clamped the TDR on the end of the cable. Question is this used in the electrical industry?
the problem with trying to measure anything while the wire is on a roll / spool is it will act like a transformer because the wire is packed close to itself. A prime example was back in the days when they were skeptical of doing a transoceanic telegraph line. In theory they figured they could hook up to a spool that was 100 miles long and test each spool before laying it. It didn't work.... till they laid it the distance. (some engineer pointed out the flaw in testing) Yes, there was continuity, but the pulsing of the power (Morse code) caused a change in the resistance.
Comment for the algorithm. This is an excellent explanation of the problems with low voltage. Especially the bad effects it can have on motors. Thanks!👍🏾
You should do a companion video specific to residential service, where it’s not uncommon to see a voltage drop of 6v or more on a 120v circuit under a 15 amp load, with the circuit verifiably NEC compliant.
I just completed one of my longest runs on my house re-wire. I calculated the drop and used a 10ga home run, so that I could use easier to manage 14ga for the short runs that make up the 15A circuit. I was expecting up to 2-2.5% loss, but *gained one volt* compared to what's at the panel. That's FREE ELECTRICITY and c'ain't nobody tell me otherwise :)
I almost didn't watch this, since I thought I understood voltage drop. But I'm glad I did watch. Your explanations of the math were great. Plus I loved hearing your personal experiences with it. Thanks for the great video.
We had trouble once lifting a 5000lb boat with a rated 6000lb hoist. We called the manufacturer and was told their 6000lb hoist is rated when the cable is on the first wrap on the drum and is derated on each subsequent wrap. Who knew! Another calculation to consider.
Thanks , great to know! i recently tested a 20A line in my home. Normally it measures a steady 121VAC (no load), but with about 16A of load i was surprised the voltage dropped to about 118V. From what i understand this is not unusual ( test was done with a toaster and AC)
One thing you need to consider in the boat lift situation is that the motor with the full load rating of 15 amps, is going to take ~5 times that current to start. It was probably a capacitor start motor, which gives it a bit of a "kick start" but that's really only to get you over the hump as the motor accelerates. If you redo the calculation at the inrush current of about 65 amps, you will see that at start up, the voltage drop will be over 30 volts! That's a 25% voltage drop!! As the motor comes up to speed, the current should quickly drop off and the voltage drop will then decrease. I would guess, that it just might have started and ran without any load on it, but even then, it would probably take at least few seconds to come up to speed, so that would still be a bit of an iffy proposition.
Great video. When in residential applications, do electricians plans for voltage drop in homes? For example, if they had a very long run to a dryer, how would they overcome the voltage drop? Would they oversize the conductor to prevent it from dropping so much for the long run? Additionally, is it possible that if you know you're going to experience a voltage drop, to intercept the wire with a step up transformer to step up the voltage to get it to where it needs to go? Is that common?
Awesome Video's, Its very different here in the UK but its interesting how other electricians work. Very entertaining and its great what you do for other sparks in the USA. Keep up the good work Dustin 👍
This is the closest video I found to my issue so I'll leave my question here: I'm getting a constant over voltage from the power company, around 135v - 145+v. What is the best way to regulate the voltage for the whole house?
Driveway lights! I did pretty much the same thing. Loooooong windy ass driveway worked to my advantage. Friend of a neighbor deal, they told me make it look good and tell us what it cost. They had a transformer/timer by the front door that powered lights on the front porch and steps. The transformer was big enough for 24 lamps but not 200' to the end of the drive. I was putting 12v light on a path to the dock so I brought the 120v out of the concrete foundation on the side of the house (right next to the main too!), the drive curved that way and was about 40' to my junction box the dock lights transformer mounted on. I put a 1" galvanized steel pipe in some concrete and mounted a third transformer to the pipe and buried some 12ga UF wire. They gave me a bonus because my pipe had a GFCI outlet on it. They like putting Christmas lights on a decorative wagon in the yard and one of those Santa things too. Now they used two short extensions.
My first house was an old farm house that had a garage 100 ft away. I ran a 12 gauge /20 amp circuit to the garage with a total cable run of about 180 ft. I installed one of those old mercury vapor lights that when you turned them off it took 20 minutes of cooldown time before they would light up again. I also has a 1 HP table saw and I noticed that when I used the saw at night every time I turned the saw on the light went out due to low voltage/ voltage drop. I noticed that your boat lift motor was dual voltage. I have always found that running big motors and high wattage heaters on 240 volt (if possible) is always more efficient. When your ripping large lumber that motor is working hard and I was tripping the motor circuit breaker. Haven’t had an issue since I switched to 240.
To see voltage drop in the real world get a plug in device that shows the voltage. Like a kilowatt or a Klein plug tester. Plug that into the bottom plug of a receptacle. Then plug a lamp into the top plug and turn it on. You should not see the voltage change. Unplug the light and plug in a hairdryer. You will see a voltage drop from the hairdryer. Record those numbers. Now switch receptacles trying to stay on the same circuit. When you plug in the hairdryer write down how much voltage drop there was. If it was more than the first test then that receptacle is farther from the circuit breaker panel than the first plug.
Wow, I like the way you explain things, I can see a veteran guy in his field, which in this case is electricity. Good job with the video! take care sir!!
Thanks for this video, we need more videos like this one with so much information, if you can we need a video explaining what reactance and impedance is. And I just wanna thank you big time for all your videos they have helped me a lot. Once again thank you so much for your time and all your videos.
Hey Dustin, I have a complicated installation, I have to run 750ft /120v for a gate system. But I have some questions about the voltage drop. Can you reach me back, I always follow your videos and I think you are very good explaining everything. I need some help with this project.
It's interesting to see how this works for AC. I've been doing car stereos for 20 years and have the calculations in my head for how many AWG for how many feet in both CCA and OFC
Could you do a video on diagnosing voltage drops actually found in houses? Suppose I put a 10-amp load on a circuit and the voltage goes down 10 volts. That indicates a poor connection somewhere along the line, right?
Did you measure the actual voltage on the motor of your boat lift when it had the problem (while it was running)? That would have been interesting to see and was likely a good bit more than your calculated 7.2 V drop.
More details on motors... A/C motors burn up with voltage drops because, unlike DC motors, they don't slow down with a voltage drop. Their speed is set by the A/C frequency (60 hz), not by the voltage. Two pole AC motors run at 3600 RPM (60 hz times 60 seconds in a minute), while 4 pole motors run at half that, or 1800 RPM, 6 pole motors at 1/3 the speed, or 1200 RPM. Those are the normal speeds you will see for A/C motors in North America for 60 Hz power. But the nameplate RPM will often be a little less because they do "slip" under load to slightly lower values. A motor under load needs a fixed amount of energy to keep spinning at its rated speed. Watts measures how much electrical energy the motor is using. Watts are volts times amps, so when voltage drops, the motor must pull more amps to keep the mechanical energy output of the motor the same. An A/C motor that is pulling 10 amps at 120 volts is using 1,200 watts. When the voltage drops to say 100 volts because you are trying tor run it on a long undersized extension cord, the motor will need to pull 12 amps at 100 volts to get all the energy it needs to keep spinning. But, because more amps mean more voltage drop, the voltage drops even more, so the motor must draw even more current, which means more voltage drop. It can get ugly fast. The motor will soon be pulling more current than the branch circuit or motor, or cord can tolerate. Everything heats up and melts. If you are lucky, the breaker pops and protects the motor from melting. But if you are unlucky, and the breaker is too large to save the motor, and your 10 amp motor stars pulling 18 amps on a 20 amp circuit, and the windings in the motor will overheat and melt the insulation, windings then short out, and the motor is toast. (assuming the motor doesn't have over-heat protection built-in). In residential applications, this is seldom a problem because the motors used are normally too small, and they are built to withstand large voltage drops, such as vacuum cleaners. Your HVAC compressors could have issue, but they are internally proteded to prevent issues (they cut off on their own when overheated from large current draws). What is more likely to be a problem in home settings is big shop tools (like a big table saw, or air compressor), which may not have overhead protection, run on undersized wires or extension cords. One can burn out their motors by using undersized building wire, or too small and too long of an extension cord. Running undersized feeders to a shop is a great way to mess up shop tools. In industrial applications, big motors are everywhere (5 hp, and up), and they must be wired and protected correctly from overload and voltage drop issues. They commonly not only have a breaker on the branch feeding them, but will also have a dedicated motor controller, which has a setable current trip point (works as a settable slow acting circuit breaker) to save the motor when it's put under too high a load or draws too much current because of voltage drop problems. The motor controller is set to trip just over the highest normal current the motor will need to draw in normal use. See NEC Article 430 Motors, Motor Circuits, and Controllers for all the code details on this subject.
Well stated! I designed a branch circuit to a fuel pump based on footage from panel to pump. In the field, the owner requested the pump be controlled by a switch installed in an office a considerable distance from the panel. The PM priced the change and had the switch installed. The pump burned out after a couple months after they moved in.
In Lakeland, FL, their outdated power grid is so bad, that when someone’s central AC would turn on, (I noticed this while walking my dog while on vacation) the nearby sodium vapor streetlights would go out temporarily due to the excessive voltage drop caused be the compressor’s starting current. Undersized city wiring and transformers were the culprit❗️ Inadequate gauge cable + modern day current demand = a very poor local power grid.
Yes actually. Mostly of the time stranded copper will have slightly less impurities than solid copper wires. That said, most of the time the impurities are so small that they won’t make a difference unless the run is hundreds of feet long.
Hey Dustin I was wondering what tool belt are you using these days. I’ve been thinking about investing in boulder bag so far. Appreciate the great content as always.
Dustin, Maybe you can point me in the right direction. I have a boat lift and I am getting 120 volts to my lift box. However, when I press the up or down lever to engage the volts drop to 6. I disengage the up/down button and it reads 120 again. I do here the clicking which indicates there is enough power to the box but it once it drops the lift does not move. Do you have a suggestion that can help me. Let me say this. During the recent Hurricanes here in Florida I am 100% sure water got into the box. I am not sure if it was salt water or water from the rain. I live in a condo complex and the power was turned off. All said can you suggest what I might be able to do before calling an expert? Thank you, Coach Cap
At first, I was curious about tgis post like it was bad thing. But as I watched further I see there is a big difference between the decrease in voltage going a load versus the calculated drop created by a load in a circuit. Basically, the difference between a DC circuit an AC circuit from my perspective.
One of the key takeaways here is that a motor, overloaded and undervoltaged, draws *more* amps than normal (quite a lot more), making the voltage drop problem even worse!
21:59 A question for those electrical engineers: is it possible to use a motor rated for 100-120v for a boat lift. If I was designing high end boat lifts, it would make sense to have a motor that accommodates voltage drop for two reasons. 1. Most boat lifts are located at a great distance from an electrical service. 2. Low voltage at the motor will cause premature failure of the motor. Having a motor rated for 115v seems like it does not give much consideration to these factors.
At Jersey Central Power & Light the tariff voltage in NJ is 120 volt basis +/- 5% or 114 to 126 volts **as measured at the load side terminals of the residential meter pan**. Some states uses a +/- 6% standard. Note that the voltage at the load center inside the home and beyond is a function of, 1.) loads, 2.) conductor sizes and lengths of runs. When a customer complains of low voltage we would install a recording voltmeter at the meter AND on occasion a second recording device inside the home as a courtesy. If at any time the voltage is under 114 at the meter for 5 minutes (sustained) or more we'd take corrective action. If we supply tariff voltage, not below 114 (not over 126) and the customer experiences let say 111 in some locations within the home, it's the customer's responsibility to have a licensed electrician address the issue. Retired reliability engineer; First Energy, JCP&L Co.
When would you change the size of wire or use a buck and boost transformer? How would you size a buck and boost? I had a similar issue at my home and just changed the wire to a much larger gauge but curious to know the options.
Total length of the circuit, not just to the switch. Especially if the motor has 12 awg stranded. Also, consider starting amps for motor, which is an inertial voltage drop due to mechanical energy loss. It's all just energy, but knowing how to think through a circuit, is key to knowing voltage drop.
Speaking of voltage tolerance for equipment. I'm not sure what our published voltage tolerance is for the equipment that we manufacture, but I know that we test to +/- 10%. That 10% is our published specification plus some amount of margin.
If the DC run lights are wired in parallel then you won’t experience the symptom you described where the light furthest down the line is the dimmest. From my experience most DC lighting that you find on boats, cars, trailers, etc, are all wired in parallel.
A higher voltage system driving a load with the same power will have lower current, so lower voltage drop for the same wires. A dual voltage 1HP motor will have roughly half the current draw at 240 vs 120. So with the same wires, it would experience half the voltage drop and 1/4 the power dissipated in the wires. This is the primary reason why higher power systems use higher voltage. Doubling the voltage reduces transmission loss by 75%, all things being equal.
Will changing the wire size on a long run only 80-90% of the distance fix the voltage drop issue or does the whole run have to change. For example on a 600’ run can you use 3/0 for 575’ and 1/0 for the remaining 25’? 208 volts 150 amp
Alright so, I'm planning for a 5 amp gate opener, some outlets for the gate opener which could also be used to run a 15amp tool here and there, but its about 75 ft from my house and from the outside of the house to the inside breaker panel will be about 30-35ft im thinking basically account for the 15amp tool plus some, so I'd run 8 gauge copper 35 ft to get outside, then turn it down to 10 gauge copper where I'm planning a pole light that might use another let's say 2 amps tops, which is 40 ft and then the rest of the distance about 35 ft would be 12 gauge to the outlet (powering the opener) obviously hypothetical... not asking for any other reason than understanding better.
Since the boat lift motor was dual voltage rated. Why did you not rewire the boat lift for 230v, assuming you had 230v available at the source. Secondarily I assume the insulation was not rated 600v. If the insulation was rated 600v or higher, you could have installed transformers and run the feeder at higher voltage to reduce the voltage loss.
We are redoing out kitchen. I am running 1/0 feeder for a 125A sub that will be in the kitchen. The main is 80' as the wire flys... so a sub made more sense than 80-100' of romex. during demo, had to some of the wiring, boy was that a rats nest. But basically after sorting out the wires, the run from the main was so bad that you couldn't run the coffee maker and toaster. I swear there must have been two breakers on one circuit... like a parallel circuit. because once I made that one run, a single run, we lost capacity.
How would voltage drop effect a motion sensor ? I was installing a sensor for a project and it seemed to have a delay when cutting off (even after adjusting the time setting). After it shut off I stepped back into the area to retest the time efficiency and it worked perfectly functional. I’m now wondering did it behave that way because of voltage drop, some sort of circuit adjustment, or was it the motion switch itself ?
The boathouse and Doc situation sounds like it would’ve been more efficient to have recommended a propane powered generator with a remote start capability. That much copper in that size of conductor is ginormous expensive.Next time, call Hank Hill for propane and propane accessories
Hi, Great channel.....Unrelated question......If I can 3D model the foundation and every 2x4, outlet and pex run and roof covering and truss etc. ...........could I theoretically get pre-approval for inspection? (assuming all is installed as per 3d CAD as they were presented originally?)
When I charge my Tesla on my nema 14-50 outlet the car shows about 243 volts with no load and about 233volts when charging at 40 amps. Is this normal and acceptable amount of voltage drop.
The Boat Lift: fyi - starting current on motors, even with a soft start, can be INSANELY high ...until the motor spins up. We had 150 Hp motors running grinders at a factory, and they would draw nearly a 700 amps at spin up. The inrush current on large motors is horrid. We had to coordinate our starts.
@@RR42636 yes. And I am working from memory (1999). Concept is sound, though. Inrush is stunning. Common starters for electric motors use a "slow blow" breaker to survive inrush. Brutal solution, and the expensive (but helpful) soft-start units don't entirely disappear the problem.
Wait! I thought a voltage drop was when an electrician with “butter fingers” who is working on a live circuit goes “Oops, the wire slipped out of my hand. Be careful.” 😂
I’m wondering how to calculate voltage drop for the main service wires. Where I live, our utility meters are usually a few hundred feet away from our main load center. And then the transformer is another few hundred feet away. So when factoring in distance to the equation, do I use the total distance from the transformer to the load center or just from the meter?
Typically, the utility company wires are not your responsibility to consider and they do their own calculations to deliver power to a meter. Here in Austin we submit a proposal for what conductors we'd like to use and they look at everything and if they see a problem they'll address it. Just depends on the situation really. If you're responsible for installing the secondary wires from a pad mounted transformer 300 ft away from a meter, yes you need to upsize for voltage drop, especially if there's several hundred more feet of conductors going in to other buildings. The more loads on the system, the worse the drop will be, so keep that in mind with the types of structures you're wiring. For most instances your responsibility for voltage drop begins at the service point where their wires hook up to yours through the rest of the system. Being ahead of the curve, however, I would definitely factor that in when building a service if I think there's going to be a drop.
so with in regards to filling breakers up to 80%, what code article would you use to support that? I was made aware of 230.208(B). Do you know of any code that says "you shall not fill breakers past 80%?"
Aren't drop calculations made using total run? In other words in your boat dock example, wouldn't you use 950 feet instead of 475? I am not a pro, so I do not know for certain. Thanks.
Is my issue a voltage drop issue? We've been noticing lately (Within the last month) that the power in the whole home fluctuates. We know this as all the lights in the home will dim and every fan in the home slows down for a few seconds and then the lights will get brighter and the fans go faster for a couple / few minutes and then just repeats over and over. This is with our normal usage in the home. Now if we turn off many things around the home it does this less. If we use our toaster oven, Fry Vats, or Micro wave it goes though this sycle even faster. So same thing but more often in a shorter amount of time. Both toaster oven and microwave are on separate circuits. I have outlet testers and they all check out fine except one that I have since fixed. The issue still persists. No breakers pop, there are no smells, no sparking sounds or visible markings of any kind like burnt outlets and what not. Like I mentioned above this effects the whole home, so lights and outlets in every room on every circuit is effected.
A momentary light dimming will happen with a furnace motor(s) start, or especially when AC starts up. This is worse when furnaces are dirty/clogged and/or AC units are not running well. Any big power draw will cause a quick dimming or flicker, but should only be caused by HVAC equipment or something like a microwave or vacuum starting. This is worse in older homes but this should last for less than a second or two. Beyond that, terminals may be loose, a motor may be going bad and drawing high current, wiring may be botched, etc. First and forement, make sure the HVAC is off and if it persists, you have a problem
Energy can not be destroyed. A loss of voltage is a loss of energy. So where did it go on a long line set ?, heat. Might not of been enough to measure, but it was heat.
Instead of using much larger wire to mitigate voltage drop over long distances... why don't folk's use a transformer near the load to bring the voltage where it needs to be? Seems like that would cost less than increasing wire size, conduit size, etc.
I have a question concerning the motor portion. Over the years I've always been told that the reason a lot of the motors we get power to are rated at 460v and not the 480v that we're bringing to it, is to go ahead and account for any voltage drop coming from the utility company to the building and then over to the location where the motor is being installed and that some over voltage in this situation is perfectly fine. Do you or anyone else here know if this is factual or not?
The short answer is "yes" it accounts for a 4% voltage drop of nominal voltage from the utility. NEMA standards are 10%+/- of nameplate voltage. Your 460v motor has an operating range of 414 to 506 volts. Overvoltage can lead to saturation of the motor windings which will cause heating and early failure. In most cases you find low voltage rather than high though. Stay with a good quality motor and run within the voltage operating range and all should be good.
@@TnTBLACK95 ...Awesome. Thanks for the reply. I always do my calculations to make sure we're in range before we energize anything, but was just curious if it was in fact the case so that as I'm explaining it to my guys, I'm not passing along any incorrect information.
![[MV] A leap of faith...ความเชื่อใจครั้งสุดท้าย (From "Petrichor the series")](http://i.ytimg.com/vi/U1piZH2CNXA/mqdefault.jpg)
Dustin, this is why I never considered my self an an a electriction. I can bend EMT like an artist but I know better not to trust my skills to pull wire until I have a licensed electriction go over it all. This is a true trade on education of the laws of electrical physics
Glad you get it. There are a lot of "installers" in the field who think they are electricians.
@@professorg8383 do you have a J card?
@@tfun101 Back in the early 1970's completed a 7 step Electrical Apprenticeship in an industrial program and received a Journeyman's Certification. The Apprenticeship program at the time was recognized by the IBEW to be fundamentally equivalent and obtaining the IBEW Journeyman's card was mostly a formality. At he time both the IBEW and the automotive industry were recruiting our guys. I was USWA at the time so we had a pretty good package and plenty of OT available. I was considering making the move but the company offered me a position in electrical management. That included education reimbursement so I could pursue my EE degree. Our apprenticeship had included multiple EE classes at a highly recognized engineering university extension and my credit could carry over allowing a fast track path toward my degree.
I chose that option. It was a great opportunity. Sadly these kinds of things don't exist much anymore. I don't regret the decision at all. I as very much a hands-on kind of guy, but realized could accomplish much more in management and ultimately make more money too.
The choice got me into some huge projects working with the latest technologies. It was tough though because managing a full time plus job and attending school at night meant I was on the go all the time. I got my degree and continued to advance in the companies management while making a lot of contacts within the industry. Amassed a ton of CE credits ang the way through numerous manufacturer programs. I became a project engineer in a billion dollar joint venture green field project. I spent close to 15 years on the design and build of that project and was then chosen to run all the electrical and instrumentation at that facility. That included hiring and training all of our technicians and developing our own apprenticeship program. At the same time I was very involved in higher levels of corporate management. Then about 20 years ago I took full retirement and quickly joined up with an engineering company doing project engineer and project management, Probably spent 80% of my time in the field. We worked exclusively with IBEW guys. In between some big projects I got involved in doing training of our clients and also for the IBEW.
I started making a shift between project management and training. Over time, passed on a lot of big projects as project manager because these are enormous high demand roles and instead did limited consulting on them. I reduced my field work to about 20% and focused more on the engineering management side and building training programs tied to the projects. As I was aging and wanted more free time, I moved more into a consultation role. Project management is very demanding and because oi the pace, it can be a 25/7 job. (Not a typo, but an expression of the demanding role it can be.)
Tried to pick smaller projects to consult on. That included some with both commercial and residential contractor companies. That is pretty much where I lost all respect for those doing residential construction. I had never in my entire career come across such unqualified people. And the management folks were even worse than the guys on the job. I pissed off a lot of owners when I told them they were violating laws with their total disregard of OSHA and the NEC code. They even expressed that they did not care at all about this and they got paid for delivering good enough, fast and cheap. I even had one tell me that if they ever got into trouble, they'd just get out of it through bankruptcy and then build a new LLC. They told me that none of their workers had the resources to pursue any legal actions and they would destroy them in court. Absolute worst case was having to buy them off with a few thousand dollars. Almost all these guys said they would not hire IBEW guys because they wanted too much money and were more trouble than they were worth. I saw plenty of examples at several jobsites where these guys operated with the same mentality as the guys managing them.
Some of these contractors tried to bid jobs with our engineering company and they were quickly disqualified. I knew the right questions to ask in bidders meetings to where these guys showed themselves as complete idiots. Although it was not a written rule, our engineering company did not do any jobs with non IBEW workers with the exception of a few small companies specializing in IT stuff.
Ultimately, I scaled back to where I worked part time for these guys, only consulting on hand picked smallish projects or for specific limited parts of bigger jobs. Then I got offered teaching project for local community college with multiple campuses across the state. We built a program for HS kids tied to one of their technical degree program. Somewhat to my surprise, I was very well received by these kids. All the teaching had done before was with adults. Didn't know how well I would do with today's HS kids. Also sometimes doing custom classes for local companies. most of the college staff were some pretty sharp guys but only had experience in academia. They didn't get rated very high for any of there custom stuff with local companies and I was very well received. I added another dimension they did not have with their traditional staff.
Through the years as became more management and more engineer with less hands on, I missed that kind of work. So over time. I built my own shop with capabilities that make a lot of guys jealous. I do some mentoring with promising students and other wise a variety of miscellaneous stuff, including experimenting and creating some of my own stuff. Built some PLC trainers for use in my classes and always looking at making training aids for hands on labs. I also enjoy testing some of the, so called, "latest and greatest" wiring devices. Particularly stuff with questionable claims. And of course, often do a lot of repairs for friends and family. Almost always have some sort of project going that includes both mechanical and electrical skills. I get some of my mentored kids involve in these things.
I have in the past been involved in issuing opinions on NEC code changes too. My roots are in industrial and automation, however I'm a strong believer that all the electrical theory applies across all the different sub fields.
Part of my low opinion of "installer electricians" is that few have had any real training in the theory of the work they are doing. And guys who will tell me that something doesn't apply to residential wiring. My guess is they often hear about things they do being wrong and they seem to have a distaste for engineers as guys trying to make their jobs harder. Maybe it comes from being shown that they are doing something wrong. But it's something I see in a lot of guys doing residential work including things like concrete and roofing. IDK when it happened, but it used to be that most of these guys had respect for what the engineers told them and that seems rare anymore.
IDK, but I think some of this comes from the shady contractors that employ them and some may com from the fact that so manyof these guys were HS dropouts or barely graduated.
This is why they make you take an electrical theory course. So, when you install or troubleshoot, you know how and why you're doing something.
Great video Dustin. A few comments. I have done VD calls thousands of times over 35 years. If you have a motor that is 15 amps at 115 volts and have a voltage drop issue, changing the voltage to 230 volts makes a considerable difference. The 15 amps in your calculation drops to 7.5 amps.
As a designer, I’m trying to get to the correct conductor size as quickly as possible. Putting cm as denominator gives % volt drop. If you put maximum volts drop you allow as denominator(120x.03=3.6) the answer will be cm. Pick your conductor that is at or larger than the number and you are good to go. When doing lighting loads, like in parking lots, you should not calc full branch circuit load at farthest length. Start at farthest distance and the load at that point. Work your way back to the panel decreasing length and increasing the load. The reason NEC uses 3% & 5% is not only to make sure equipment will work, but that in motor circuits, the breakers can handle the increased amps.
I hope you do not mind the comments. Respectfully, Kevin
Voltage Drop Clarification:
- Simply, the voltage drop between two points on a conductor always occurs due to resistance in the conductor between those two points: longer the distance, the greater the voltage drop.
- The resistance of a conductor is determined by the resistivity coefficient of the conductor’s material and the diameter of the conductor. (Remember, current flows on the outside skin of the conductor., and voltage flows on the inside - simplistic analogy)
- In a commercial AC system, multi-phase systems have different "apparent" voltage drop per the same conductor diameter due to the “phase angle” difference
- For practical and standard analysis of voltage drop, you have to consider three things (1) material type and size of the conductors, (2) is it a DC or AC single or multi-phase system, and (3) what type of load is at the end of the conductor - purely resistive (i.e., incandescent bulb or heating element) vs. inductive load (i.e., motor, transformer, etc.)
- The simplest explanation of what the common cause of voltage drop in residential and commercial wiring systems is due to using too small of a conductor for the type and amount of power consumed in a system
That was so interesting and at the end, I was wondering how much voltage drop is acceptable because 7 volts didn't really seem that big of a deal. Then I did the math and saw that it was about 8% and realized yup, that's why that motor wasn't happy. Thx Dustin for really helping us understand this. Your knowledge and passion for the subject is evident in every video.
That is at 120v. At 240 volts it would be only a 3% drop. But at 12v that 7 volts is a 58% voltage drop. This is one of the big reasons we increase the voltage when we know there will be a voltage drop.
@@ecospider5 Voltage drop does not decrease to 3% at 240 volts. To begin with ANSI sets the national standard for voltage tolerances. There is an A and B range for voltage tolerances at the service entry. Range A is +/- 5%. This allows 5% for the utility and 5% for the customer. As for a motor, there is no such thing as a 240 volt motor. It would be a 230 volt motor that is used on a 240 system and can be utilized from 207 to 253 volts (+/- 10% of nameplate rating) per NEMA standards. These are national standards that are recognized across all industries.
Code aside, how much is acceptable depends on what the load is. Something like a battery charger might not care at all, it will just take a little longer. Lights can be very sensitive. And transferred power is what really matters, and it varies by the square of the voltage. So a small change in voltage may cause a significantly larger change in power.
@@strehlow that is also covered in a code, PST flicker. It is the perception of flicker in an incandescent light the human eye can notice. It is on a curve, the smaller the voltage drop the more events are allowable in a given amount of time.
I don't know who you are, I don't know if you're stupid, or brilliant. Do you know that you have taught me more about electrical work than any other source I have used. I cannot thank you enough. You must just love to teach to do this.
So glad I subscribed. I applied to an electrical union nearby tested, interviewed, got my placement . It’s been a little over a year, I haven’t gotten a call yet but I’m still trying to learn as much as I can and I found this and these videos have been very helpful. Thank you.
I recently went on a cruise ship. They are notorious for having few outlets and you never know which plug type you get. What I want to ask about is that they forbid surge protectors. ?? Where does ground go at sea? Google said they don't deliver 120 hot and neutral but two opposing 60v hots. I know it doesn't pertain to your target audience, but this sounds like a very interesting geek out on topic.
Years ago I helped a guy with a long run of 1,000 ft for a 240 / 120 line. He said, what can I get at the end? Went to the charts for 2/0 aluminum and came up with 50 amps before we had a 5% drop. Turned out to be right on the money when checking with a meter. For those who may argue the numbers, this was a hunk of service cable bought surplus for $1 per foot. It had a #0 neutral so there's our limiting factor when using the 120 volt legs.
I have a question. After you run the wire, if you take a voltage reading. Would it should the voltage drop? Or this is only going to happen when a load is applied?
I'm gonna call BS. 2/0 aluminum at 1000 ft and 50 amps. You will get about a13% V drop, or 104V at the meter. You would need 500 mcm to stay within 5% at 1000'.
@@TnTBLACK95 ... I was going from memory, and that 5% should have been 15%. (my mistake) Now that you mentioned this the goal was to stay above 105 volts. IOW, my draw had to be well under 50 amps. Again, going from memory.... I recall loading one leg at a time and the real numbers for continuous draw were probably in the 40 amp range with something closer to 110 volts. These days the service is used for other things and real draw is under 20 amps a leg. Of course, we also cut the feed short so now just under 800 ft. Since this thread is about how to avoid voltage drop I will mention that one guy thought we could do the run in #6 wire... till we had a little talk about using the charts. Charts are a handy thing to have!
@@rupe53 that makes a lot more sense. lol I'm a power quality tech for the utility company and run into these types of situations regularly. To save money a secondary will be extended to serve a new customer or these old houses are being remodeled with multiple hvac units. Since engineers go by what "their book says" I downloaded a pretty handy app for figuring wire size, load drop, power factor, resistance....
Awesome video. You talking about motor loads brought up another possible video idea. Talk about motor starters and overloads. A/C motors and D/C motors. Soft starts. Motor load conductor sizing … keep up the great work. I look forward to these videos every Monday and Wednesday 👍
I took two semesters of electronic technology…quit because I could NOT understand it…mostly due to the worst teacher I’ve ever had. You have easily made me understand this wizardry easily in twenty minutes. Amazing teaching ability!
good lesson...voltage drop is one of those things often overlooked as to why something is acting weird..
Dustin's videos are always so informative and he makes everything so easy to understand. I wish these videos existed when I was an apprentice. This is a good lesson on why you should always take your own measurements.
Thanks for that info. I am in the process of designing a wiring panel to a pond area that is about 250 ft. from the main panel and I was trying to figure out how to estimate the voltage drop over that distance and size my wire correctly. Great content, keep it coming!!!
This video is very reason why I hate most extension cords! Not heavy enough for the distance or the load requirement. Plus, you get situations where people daisy chain the smaller gauge cords.
Hey Dustin, I’m a huge fan, really support what you do. I’m a fellow sparky who does mostly residential. Could you please do a video on fire alarms if you can and explain the different systems. I would really love to learn more
Thanks for your thorough patience for us of the OLDER generation! I've learned tons from you! I used to say I knew enough to be dangerous. Now I understand why that was a true statement! Thanks for making me a safer person!
You da man!
Steve
Now you stray into Power Quality.
Yes, voltage changes over the season and maybe by the day - week day vs. week end.
Very good lessons.
very good topic. I was waiting for you to address voltage drop due to weak connection: wire nut error, wrong torque on a buss bar, etc. That said, focusing on proper conductor size & type over a specific distance - very useful and valuable vid. Thank you for doing that.
A+
I truly appreciate and love how well you explain things even to the person who already understands it already. Thank you kindly and greatly appreciate you and your Chanel!
Cable length and faults Can be accurately be measured with a, TDR "Time domain reflectometers" In the IT industry, cable TV and radio systems We can accurately locate faults and determine exact lengths of conductors. Have a spool of wire want to know how long it is, clamped the TDR on the end of the cable. Question is this used in the electrical industry?
the problem with trying to measure anything while the wire is on a roll / spool is it will act like a transformer because the wire is packed close to itself. A prime example was back in the days when they were skeptical of doing a transoceanic telegraph line. In theory they figured they could hook up to a spool that was 100 miles long and test each spool before laying it. It didn't work.... till they laid it the distance. (some engineer pointed out the flaw in testing) Yes, there was continuity, but the pulsing of the power (Morse code) caused a change in the resistance.
Comment for the algorithm.
This is an excellent explanation of the problems with low voltage.
Especially the bad effects it can have on motors.
Thanks!👍🏾
Love what you have done with the videos you have made, you will be helping alot of apprentices out there. Keep it up!
You should do a companion video specific to residential service, where it’s not uncommon to see a voltage drop of 6v or more on a 120v circuit under a 15 amp load, with the circuit verifiably NEC compliant.
I just completed one of my longest runs on my house re-wire. I calculated the drop and used a 10ga home run, so that I could use easier to manage 14ga for the short runs that make up the 15A circuit.
I was expecting up to 2-2.5% loss, but *gained one volt* compared to what's at the panel. That's FREE ELECTRICITY and c'ain't nobody tell me otherwise :)
I almost didn't watch this, since I thought I understood voltage drop. But I'm glad I did watch. Your explanations of the math were great. Plus I loved hearing your personal experiences with it. Thanks for the great video.
Thanks for doing the calcs and thanks for the real world story about the boat motor and the DC lights. That humanized it a lot.
We had trouble once lifting a 5000lb boat with a rated 6000lb hoist. We called the manufacturer
and was told their 6000lb hoist is rated when the cable is on the first wrap on the drum and is derated on each subsequent wrap. Who knew! Another calculation to consider.
Thanks , great to know! i recently tested a 20A line in my home. Normally it measures a steady 121VAC (no load), but with about 16A of load i was surprised the voltage dropped to about 118V. From what i understand this is not unusual ( test was done with a toaster and AC)
One thing you need to consider in the boat lift situation is that the motor with the full load rating of 15 amps, is going to take ~5 times that current to start. It was probably a capacitor start motor, which gives it a bit of a "kick start" but that's really only to get you over the hump as the motor accelerates. If you redo the calculation at the inrush current of about 65 amps, you will see that at start up, the voltage drop will be over 30 volts! That's a 25% voltage drop!! As the motor comes up to speed, the current should quickly drop off and the voltage drop will then decrease. I would guess, that it just might have started and ran without any load on it, but even then, it would probably take at least few seconds to come up to speed, so that would still be a bit of an iffy proposition.
Great video. When in residential applications, do electricians plans for voltage drop in homes? For example, if they had a very long run to a dryer, how would they overcome the voltage drop? Would they oversize the conductor to prevent it from dropping so much for the long run? Additionally, is it possible that if you know you're going to experience a voltage drop, to intercept the wire with a step up transformer to step up the voltage to get it to where it needs to go? Is that common?
Awesome Video's, Its very different here in the UK but its interesting how other electricians work. Very entertaining and its great what you do for other sparks in the USA. Keep up the good work Dustin 👍
This is the closest video I found to my issue so I'll leave my question here: I'm getting a constant over voltage from the power company, around 135v - 145+v. What is the best way to regulate the voltage for the whole house?
Driveway lights! I did pretty much the same thing. Loooooong windy ass driveway worked to my advantage. Friend of a neighbor deal, they told me make it look good and tell us what it cost.
They had a transformer/timer by the front door that powered lights on the front porch and steps. The transformer was big enough for 24 lamps but not 200' to the end of the drive.
I was putting 12v light on a path to the dock so I brought the 120v out of the concrete foundation on the side of the house (right next to the main too!), the drive curved that way and was about 40' to my junction box the dock lights transformer mounted on. I put a 1" galvanized steel pipe in some concrete and mounted a third transformer to the pipe and buried some 12ga UF wire.
They gave me a bonus because my pipe had a GFCI outlet on it. They like putting Christmas lights on a decorative wagon in the yard and one of those Santa things too. Now they used two short extensions.
My first house was an old farm house that had a garage 100 ft away. I ran a 12 gauge /20 amp circuit to the garage with a total cable run of about 180 ft. I installed one of those old mercury vapor lights that when you turned them off it took 20 minutes of cooldown time before they would light up again. I also has a 1 HP table saw and I noticed that when I used the saw at night every time I turned the saw on the light went out due to low voltage/ voltage drop. I noticed that your boat lift motor was dual voltage. I have always found that running big motors and high wattage heaters on 240 volt (if possible) is always more efficient. When your ripping large lumber that motor is working hard and I was tripping the motor circuit breaker. Haven’t had an issue since I switched to 240.
To see voltage drop in the real world get a plug in device that shows the voltage. Like a kilowatt or a Klein plug tester. Plug that into the bottom plug of a receptacle. Then plug a lamp into the top plug and turn it on. You should not see the voltage change. Unplug the light and plug in a hairdryer. You will see a voltage drop from the hairdryer. Record those numbers.
Now switch receptacles trying to stay on the same circuit. When you plug in the hairdryer write down how much voltage drop there was. If it was more than the first test then that receptacle is farther from the circuit breaker panel than the first plug.
Man I could binge these videos all day. Thank you!
Wow, I like the way you explain things, I can see a veteran guy in his field, which in this case is electricity. Good job with the video! take care sir!!
Thanks for this video, we need more videos like this one with so much information, if you can we need a video explaining what reactance and impedance is. And I just wanna thank you big time for all your videos they have helped me a lot. Once again thank you so much for your time and all your videos.
Perfect timing needed this
You are the best, my friend. Thanks for the time sharing and teaching us...
Dustin this one's on the fly.but In a locked rotor situation wouldn't the resistance (inductance) go up?
Hey Dustin, I have a complicated installation, I have to run 750ft /120v for a gate system. But I have some questions about the voltage drop. Can you reach me back, I always follow your videos and I think you are very good explaining everything. I need some help with this project.
It's interesting to see how this works for AC. I've been doing car stereos for 20 years and have the calculations in my head for how many AWG for how many feet in both CCA and OFC
Ur a car guy not an electrician
Could you do a video on diagnosing voltage drops actually found in houses? Suppose I put a 10-amp load on a circuit and the voltage goes down 10 volts. That indicates a poor connection somewhere along the line, right?
Why is AL used from the meter to the Main breaker box? One would think it should be copper. ??
Topic in the right time for me.
Wouldn't current in a locked rotor be limited by the impedance of the circuit?
Did you measure the actual voltage on the motor of your boat lift when it had the problem (while it was running)? That would have been interesting to see and was likely a good bit more than your calculated 7.2 V drop.
More details on motors... A/C motors burn up with voltage drops because, unlike DC motors, they don't slow down with a voltage drop. Their speed is set by the A/C frequency (60 hz), not by the voltage. Two pole AC motors run at 3600 RPM (60 hz times 60 seconds in a minute), while 4 pole motors run at half that, or 1800 RPM, 6 pole motors at 1/3 the speed, or 1200 RPM. Those are the normal speeds you will see for A/C motors in North America for 60 Hz power. But the nameplate RPM will often be a little less because they do "slip" under load to slightly lower values.
A motor under load needs a fixed amount of energy to keep spinning at its rated speed. Watts measures how much electrical energy the motor is using. Watts are volts times amps, so when voltage drops, the motor must pull more amps to keep the mechanical energy output of the motor the same. An A/C motor that is pulling 10 amps at 120 volts is using 1,200 watts. When the voltage drops to say 100 volts because you are trying tor run it on a long undersized extension cord, the motor will need to pull 12 amps at 100 volts to get all the energy it needs to keep spinning. But, because more amps mean more voltage drop, the voltage drops even more, so the motor must draw even more current, which means more voltage drop. It can get ugly fast. The motor will soon be pulling more current than the branch circuit or motor, or cord can tolerate. Everything heats up and melts. If you are lucky, the breaker pops and protects the motor from melting. But if you are unlucky, and the breaker is too large to save the motor, and your 10 amp motor stars pulling 18 amps on a 20 amp circuit, and the windings in the motor will overheat and melt the insulation, windings then short out, and the motor is toast. (assuming the motor doesn't have over-heat protection built-in).
In residential applications, this is seldom a problem because the motors used are normally too small, and they are built to withstand large voltage drops, such as vacuum cleaners. Your HVAC compressors could have issue, but they are internally proteded to prevent issues (they cut off on their own when overheated from large current draws).
What is more likely to be a problem in home settings is big shop tools (like a big table saw, or air compressor), which may not have overhead protection, run on undersized wires or extension cords. One can burn out their motors by using undersized building wire, or too small and too long of an extension cord. Running undersized feeders to a shop is a great way to mess up shop tools.
In industrial applications, big motors are everywhere (5 hp, and up), and they must be wired and protected correctly from overload and voltage drop issues. They commonly not only have a breaker on the branch feeding them, but will also have a dedicated motor controller, which has a setable current trip point (works as a settable slow acting circuit breaker) to save the motor when it's put under too high a load or draws too much current because of voltage drop problems. The motor controller is set to trip just over the highest normal current the motor will need to draw in normal use. See NEC Article 430 Motors, Motor Circuits, and Controllers for all the code details on this subject.
Well stated! I designed a branch circuit to a fuel pump based on footage from panel to pump. In the field, the owner requested the pump be controlled by a switch installed in an office a considerable distance from the panel. The PM priced the change and had the switch installed. The pump burned out after a couple months after they moved in.
Vacuum cleaner motors are brushed motors, not asynchronous ones like in industrial applicstions. They will just slow down with undervoltage.
In Lakeland, FL, their outdated power grid is so bad, that when someone’s central AC would turn on, (I noticed this while walking my dog while on vacation) the nearby sodium vapor streetlights would go out temporarily due to the excessive voltage drop caused be the compressor’s starting current.
Undersized city wiring and transformers were the culprit❗️
Inadequate gauge cable + modern day current demand = a very poor local power grid.
Hey Dustin, question, does copper that is in the conductors have different grades of purity? Less pure, more resistance? More pure, less resistance?
Yes actually. Mostly of the time stranded copper will have slightly less impurities than solid copper wires.
That said, most of the time the impurities are so small that they won’t make a difference unless the run is hundreds of feet long.
If you change the wire size for voltage drop, do you also need to change the breaker size?
Hey Dustin I was wondering what tool belt are you using these days. I’ve been thinking about investing in boulder bag so far. Appreciate the great content as always.
Dustin, Maybe you can point me in the right direction. I have a boat lift and I am getting 120 volts to my lift box. However, when I press the up or down lever to engage the volts drop to 6. I disengage the up/down button and it reads 120 again. I do here the clicking which indicates there is enough power to the box but it once it drops the lift does not move. Do you have a suggestion that can help me. Let me say this. During the recent Hurricanes here in Florida I am 100% sure water got into the box. I am not sure if it was salt water or water from the rain. I live in a condo complex and the power was turned off. All said can you suggest what I might be able to do before calling an expert? Thank you, Coach Cap
Awesome video!, very informative. Thank you for taking the time to create this video! 👍 👍
At first, I was curious about tgis post like it was bad thing. But as I watched further I see there is a big difference between the decrease in voltage going a load versus the calculated drop created by a load in a circuit. Basically, the difference between a DC circuit an AC circuit from my perspective.
One of the key takeaways here is that a motor, overloaded and undervoltaged, draws *more* amps than normal (quite a lot more), making the voltage drop problem even worse!
21:59 A question for those electrical engineers: is it possible to use a motor rated for 100-120v for a boat lift. If I was designing high end boat lifts, it would make sense to have a motor that accommodates voltage drop for two reasons. 1. Most boat lifts are located at a great distance from an electrical service. 2. Low voltage at the motor will cause premature failure of the motor. Having a motor rated for 115v seems like it does not give much consideration to these factors.
At Jersey Central Power & Light the tariff voltage in NJ is 120 volt basis +/- 5% or 114 to 126 volts **as measured at the load side terminals of the residential meter pan**. Some states uses a +/- 6% standard. Note that the voltage at the load center inside the home and beyond is a function of, 1.) loads, 2.) conductor sizes and lengths of runs. When a customer complains of low voltage we would install a recording voltmeter at the meter AND on occasion a second recording device inside the home as a courtesy. If at any time the voltage is under 114 at the meter for 5 minutes (sustained) or more we'd take corrective action. If we supply tariff voltage, not below 114 (not over 126) and the customer experiences let say 111 in some locations within the home, it's the customer's responsibility to have a licensed electrician address the issue. Retired reliability engineer; First Energy, JCP&L Co.
Thanks for the video. For electric motors, most the surge/starting current demand be factored into the voltage drop calculations?
When would you change the size of wire or use a buck and boost transformer? How would you size a buck and boost? I had a similar issue at my home and just changed the wire to a much larger gauge but curious to know the options.
I'm in school for this and now I'm understanding some of this 😁
Total length of the circuit, not just to the switch. Especially if the motor has 12 awg stranded. Also, consider starting amps for motor, which is an inertial voltage drop due to mechanical energy loss. It's all just energy, but knowing how to think through a circuit, is key to knowing voltage drop.
Speaking of voltage tolerance for equipment. I'm not sure what our published voltage tolerance is for the equipment that we manufacture, but I know that we test to +/- 10%. That 10% is our published specification plus some amount of margin.
Thank you for sharing your knowledge.
If the DC run lights are wired in parallel then you won’t experience the symptom you described where the light furthest down the line is the dimmest. From my experience most DC lighting that you find on boats, cars, trailers, etc, are all wired in parallel.
A higher voltage system driving a load with the same power will have lower current, so lower voltage drop for the same wires. A dual voltage 1HP motor will have roughly half the current draw at 240 vs 120. So with the same wires, it would experience half the voltage drop and 1/4 the power dissipated in the wires.
This is the primary reason why higher power systems use higher voltage. Doubling the voltage reduces transmission loss by 75%, all things being equal.
Will changing the wire size on a long run only 80-90% of the distance fix the voltage drop issue or does the whole run have to change. For example on a 600’ run can you use 3/0 for 575’ and 1/0 for the remaining 25’?
208 volts
150 amp
it’s impedance for AC and resistance for DC… fortunately AC was the adopted method and can be stepped up and down easier than with DC
Alright so, I'm planning for a 5 amp gate opener, some outlets for the gate opener which could also be used to run a 15amp tool here and there, but its about 75 ft from my house and from the outside of the house to the inside breaker panel will be about 30-35ft im thinking basically account for the 15amp tool plus some, so I'd run 8 gauge copper 35 ft to get outside, then turn it down to 10 gauge copper where I'm planning a pole light that might use another let's say 2 amps tops, which is 40 ft and then the rest of the distance about 35 ft would be 12 gauge to the outlet (powering the opener) obviously hypothetical... not asking for any other reason than understanding better.
Since the boat lift motor was dual voltage rated. Why did you not rewire the boat lift for 230v, assuming you had 230v available at the source.
Secondarily
I assume the insulation was not rated 600v. If the insulation was rated 600v or higher, you could have installed transformers and run the feeder at higher voltage to reduce the voltage loss.
We are redoing out kitchen. I am running 1/0 feeder for a 125A sub that will be in the kitchen. The main is 80' as the wire flys... so a sub made more sense than 80-100' of romex. during demo, had to some of the wiring, boy was that a rats nest. But basically after sorting out the wires, the run from the main was so bad that you couldn't run the coffee maker and toaster. I swear there must have been two breakers on one circuit... like a parallel circuit. because once I made that one run, a single run, we lost capacity.
What's a good place to buy a code book from? The ones on amazon have horrible reviews on quality is that normal?
How would voltage drop effect a motion sensor ? I was installing a sensor for a project and it seemed to have a delay when cutting off (even after adjusting the time setting). After it shut off I stepped back into the area to retest the time efficiency and it worked perfectly functional. I’m now wondering did it behave that way because of voltage drop, some sort of circuit adjustment, or was it the motion switch itself ?
The boathouse and Doc situation sounds like it would’ve been more efficient to have recommended a propane powered generator with a remote start capability. That much copper in that size of conductor is ginormous expensive.Next time, call Hank Hill for propane and propane accessories
Hi, Great channel.....Unrelated question......If I can 3D model the foundation and every 2x4, outlet and pex run and roof covering and truss etc. ...........could I theoretically get pre-approval for inspection? (assuming all is installed as per 3d CAD as they were presented originally?)
Runway lighting systems have huge, fridge sized voltage regulators because of this!
As a kid I was told that electric motors are filled with smoke and if you let the smoke out it won't work any more
When I charge my Tesla on my nema 14-50 outlet the car shows about 243 volts with no load and about 233volts when charging at 40 amps. Is this normal and acceptable amount of voltage drop.
The Boat Lift: fyi - starting current on motors, even with a soft start, can be INSANELY high ...until the motor spins up. We had 150 Hp motors running grinders at a factory, and they would draw nearly a 700 amps at spin up. The inrush current on large motors is horrid. We had to coordinate our starts.
Hey Jeff, we’re these with soft starters?
@@RR42636 yes. And I am working from memory (1999). Concept is sound, though. Inrush is stunning. Common starters for electric motors use a "slow blow" breaker to survive inrush. Brutal solution, and the expensive (but helpful) soft-start units don't entirely disappear the problem.
I was needing this video I sent you DM on Instagram to see if you had any videos on voltage drop. And here it is
Wait! I thought a voltage drop was when an electrician with “butter fingers” who is working on a live circuit goes “Oops, the wire slipped out of my hand. Be careful.” 😂
So do you take apprentice or do you only offer the membership?
That is why box store air compressors have a 5 horse power rating plugged into 15 amp outlet. 15 amps at 120 voltage 2 hp.
What was the reason for not wiring the motor for 240v? Running oversized conductors will get you more torque out of the motor.
Uh, what?
So if I upsize my wires AND upside my breaker/ fuses I magically get more torque?
@@that1electrician 240 would pull less amperage, so take it easy. internet sandbox bully
I’m wondering how to calculate voltage drop for the main service wires. Where I live, our utility meters are usually a few hundred feet away from our main load center. And then the transformer is another few hundred feet away. So when factoring in distance to the equation, do I use the total distance from the transformer to the load center or just from the meter?
Typically, the utility company wires are not your responsibility to consider and they do their own calculations to deliver power to a meter. Here in Austin we submit a proposal for what conductors we'd like to use and they look at everything and if they see a problem they'll address it. Just depends on the situation really. If you're responsible for installing the secondary wires from a pad mounted transformer 300 ft away from a meter, yes you need to upsize for voltage drop, especially if there's several hundred more feet of conductors going in to other buildings. The more loads on the system, the worse the drop will be, so keep that in mind with the types of structures you're wiring. For most instances your responsibility for voltage drop begins at the service point where their wires hook up to yours through the rest of the system. Being ahead of the curve, however, I would definitely factor that in when building a service if I think there's going to be a drop.
on a 3 phase, what if you have 2 wires for ex. " on a 2-#12 solid uncoated type thw ..... does the k increase to 25.8 ?
I been looking into expanding my knowledge any recommendations on books that might help with installation, motors, grounding, etc?
@@Makitafan thank you I have to go through his videos
so with in regards to filling breakers up to 80%, what code article would you use to support that? I was made aware of 230.208(B). Do you know of any code that says "you shall not fill breakers past 80%?"
The 80% derating applies to continuous loads. See 210.20(A).
210.21(B2) and 210.23(A1) also mention 80% loading for cord-and-plug-connected loads.
Aren't drop calculations made using total run? In other words in your boat dock example, wouldn't you use 950 feet instead of 475? I am not a pro, so I do not know for certain.
Thanks.
2KIL multiplier of 2 is to correct that on single phase runs
It is also catastrophic, The lower the voltage the higher the current. The higher the current the more voltage drop you will have.
Great video man thank you
Is my issue a voltage drop issue?
We've been noticing lately (Within the last month) that the power in the whole home fluctuates. We know this as all the lights in the home will dim and every fan in the home slows down for a few seconds and then the lights will get brighter and the fans go faster for a couple / few minutes and then just repeats over and over. This is with our normal usage in the home. Now if we turn off many things around the home it does this less. If we use our toaster oven, Fry Vats, or Micro wave it goes though this sycle even faster. So same thing but more often in a shorter amount of time. Both toaster oven and microwave are on separate circuits.
I have outlet testers and they all check out fine except one that I have since fixed. The issue still persists. No breakers pop, there are no smells, no sparking sounds or visible markings of any kind like burnt outlets and what not.
Like I mentioned above this effects the whole home, so lights and outlets in every room on every circuit is effected.
A momentary light dimming will happen with a furnace motor(s) start, or especially when AC starts up. This is worse when furnaces are dirty/clogged and/or AC units are not running well. Any big power draw will cause a quick dimming or flicker, but should only be caused by HVAC equipment or something like a microwave or vacuum starting. This is worse in older homes but this should last for less than a second or two. Beyond that, terminals may be loose, a motor may be going bad and drawing high current, wiring may be botched, etc.
First and forement, make sure the HVAC is off and if it persists, you have a problem
Energy can not be destroyed. A loss of voltage is a loss of energy.
So where did it go on a long line set ?, heat. Might not of been enough to measure, but it was heat.
Isn’t a Loss of voltage really a lack of voltage?
@@howtodoitdude1662 No, at the breaker box you will have full voltage. Loss is at end of line set. Edit; or I should say 'loss' is IN the line set.
How are KID in 3 phase and single phase affected by the difference in US and idk EU measurements? Distance specifically
Instead of using much larger wire to mitigate voltage drop over long distances... why don't folk's use a transformer near the load to bring the voltage where it needs to be? Seems like that would cost less than increasing wire size, conduit size, etc.
2kli/cm is for DC only. Why are you adding it to 1phase ac calcs?
I have a question concerning the motor portion. Over the years I've always been told that the reason a lot of the motors we get power to are rated at 460v and not the 480v that we're bringing to it, is to go ahead and account for any voltage drop coming from the utility company to the building and then over to the location where the motor is being installed and that some over voltage in this situation is perfectly fine. Do you or anyone else here know if this is factual or not?
The short answer is "yes" it accounts for a 4% voltage drop of nominal voltage from the utility. NEMA standards are 10%+/- of nameplate voltage. Your 460v motor has an operating range of 414 to 506 volts. Overvoltage can lead to saturation of the motor windings which will cause heating and early failure. In most cases you find low voltage rather than high though. Stay with a good quality motor and run within the voltage operating range and all should be good.
@@TnTBLACK95 ...Awesome. Thanks for the reply. I always do my calculations to make sure we're in range before we energize anything, but was just curious if it was in fact the case so that as I'm explaining it to my guys, I'm not passing along any incorrect information.
Can you explain parallel runs please?
It is beneficial to know and understand the details. But in today's world, just use the app