Voltage-Drop - Manufacturer and NEC Recommendations [210.19(A) Note 3, 2020 NEC]

According to 110.3(B) in the NEC, equipment, including conductors, must be installed in accordance with the manufacturer’s instructions. But what about when the length of these conductors creates a voltage drop? Is voltage drop just a recommendation in the NEC and not really enforceable? Find out in this video where we discuss the ramifications of voltage drop in branch circuit and the energy and life safety issues that may be affected.
This video is an extract from Mike Holt’s Electrical Calculations Training Library, based on the 2020 NEC. For more information about this product visit www.MikeHolt.com/examprep or call 888.632.2633.
For almost 50 years, Mike Holt Enterprises has been providing quality electrical Code training to help electrical professionals learn the Code, prepare for exams, and improve their electrical knowledge. Visit www.MikeHolt.com​ for exam preparation tips and training, instructor and curriculum support, continuing education options, free videos and graphics, and so much more.

[@cherryg2210]

In the industry, its standard to consider 5% voltage drop from Transformer terminals right upto the consumer terminals. This ensures that we remain in an envelope inspite of source voltage fluctuations, Transformer regulation (load depended) and effect of overloading the device itself. Increasing this envelope to 10% means now you don't have much flexibility in operating the power system and voltages at load end may routinely go below 10%.

[@tekpatlizkalotekatl530]

I think some of the confusion is a result of using the term “voltage drop” when discussing ANSI 84.1. NEC Voltage drop or (rise) is a delta from voltage variable. ANSI is a voltage range (tolerance) of Nominal voltage. You can have Zero voltage drop from service to branch circuit load and be less than ANSI’s acceptable voltage “Range”, if utility voltages are too high or low.

[@johnsandlinjr]

This is fair. Because I work for a utility and our tolerance is 5% of the nominal. So we’re already giving the customer a where between 114 and 126

[@carultch]

A more accurate term would be Ohmic Voltage difference. It is the voltage difference from source to load, due to the fact that the conductors have non-zero resistance. It is the voltage necessary to cause current to flow through that section of conductor. If you're working with a power source instead of a load, it is really a voltage rise, rather than a voltage drop. But it still is a loss of power in the form of heat generated in the wires.

[@mastaplanna]

First let me say, thank you for sharing all of this knowledge...I also have to say, somewhat tongue in cheek...If you turned these videos into cartoons (a la Joe Rogan) and had the practical information being demonstrated that way with all of you guys talking in the background, oh man, I think it would be a hit...love your videos, teaching myself maybe for a new career...

[@MikeHoltNEC]

Hum....

[@cherryg2210]

One interesting aspect of voltage drop calculation is: Nobody talks about the actual load current to be used for voltage drop calcs. Motors seldom operate at their nameplate rating and the Code is clear about the basis for ampacity for cable sizing. But when it comes down to voltage drop, no standard or Code on earth tells if you need to take the nameplate rating or actual load, and there lies a flexibility to get the actual BHP value (shaft kW) and take the actual load Amps which will never be exceeded.

[@alvilla701]

I've been reading a lot, can i take the electrical exam even if i still do not complete the required hours?

[@microcolonel]

If you can, you still won't qualify for a license with that exam.

[@MrBucidart]

Question: Franklin Electric Motors tells me plus or minus 10% of 230 volts, PG&E tells me plus or minus 5% at 240 volts. Who's correct..

[@danmarafino1770]

I was under the impression the manufacturer spec is 10% of 230 volts so that it can comply not only with utility variances but also run on single phase 240V -or- 2 legs of a 3 phase 208V Wye.
230V motor - 10% = 207V
230V + 10% = 253V.
But this is supply voltage, not a voltage drop.