Proper wiring of general use receptacles

[bsmale]

I hope this post finds someone who can help lead me in the correct direction--

I am a Certified Electrical Contractor since 2003, and an Adjunct Professor at our local Apprenticeship Program (That happens to use Mike Holt's curriculum). I have found in my area and believe in general, there are VERY few contractors doing voltage drop calculations upon general use receptacles, specifically in homes; but overall, everywhere. We are allowed a maximum of 3% on branch circuits, and I find VERY few that test within spec, using a load inducer. Arc-fault requirements are becoming more prevalent, yet the actual percentage of time they do their job is low. Arc-fault breakers, I know for sure Square D, are rated at 120 volts, with a 3% tolerance—I have an email confirming this from Square D engineering. Power companies are increasing voltages on their lines to account for the increase in load, instead of fixing the cause of the problem. I personally have a customer that has random nuisance trips due to voltage spikes upwards of 126 volts—this is WAY out of tolerance for these breakers. Beyond that, on the branch circuits: If the wiring is not sized to accommodate the full load, at the farthest device, the voltage drop will put the breaker out of tolerance; and it will not function properly.

I am attempting to inform our up and coming in class, but I feel this is NO WHERE near enough; how might I go about making the largest impact upon our trade?

 

[infinity]

I have found in my area and believe in general, there are VERY few contractors doing voltage drop calculations upon general use receptacles, specifically in homes; but overall, everywhere. We are allowed a maximum of 3% on branch circuits, and I find VERY few that test within spec, using a load inducer.

There is no NEC requirement to provide voltage drop compensation on general use receptacle circuits in a home. The 3% you've mentioned is merely a suggestion. Yes there may be instances where long branch circuits end up with a lower voltage on the farthest receptacle especially under a heavy load. Testing them is not required and IMO it is not very useful simply due to the nature of how receptacles in homes are typically used.

Welcome to the Forum.

 

[bsmale]

There is no NEC requirement to provide voltage drop compensation on general use receptacle circuits in a home. The 3% you've mentioned is merely a suggestion. Yes there may be instances where long branch circuits end up with a lower voltage on the farthest receptacle especially under a heavy load. Testing them is not required and IMO it is not very useful simply due to the nature of how receptacles in homes are typically used.

Welcome to the Forum.

Hello, and thank you for your response.

I disagree. Although it is a suggestion, it is one that should be followed. Arc-fault breakers have to be within their specs to function properly. It is in our Code that we are to follow manufacturer specifications, and this would be one of them.

Besides that, if you think it is ok to allow a voltage drop of up upwards of 10%, or more under load—it is not—

I have gone behind others and seen 101 volts under load, which did not allow the equipment to function; the voltage was simply out of spec.

My question still stands as my first post stated.

 

[LarryFine]

Welcome to the forum.

Is your question about mandating voltage regulation from the POCO, or about mandating how electricians should be wiring?

We really can't do anything about the former, and the latter is more about design than code, which are separate things.

 

[Seven-Delta-FortyOne]

Sounds like a solution looking for a problem.

I have not personally encountered 10% VD ever, in a residential setting.

Power in my area is regularly 124-125 volts at the panel. I haven’t seen 120 in quite a while. Even 121-122 is getting uncommon.

AFCI breakers have questionable usefulness on a good day, so it’s not clear that a low voltage will make them function any less than they already don’t function.

 

[bsmale]

Hello, and thank you.

Truly my issue is with the wiring, but the power companies will become an issue as well.

If we as electricians cannot provide a specified voltage to a piece of unknown equipment, then what are we really doing? We have no clue what the load requirements are, therefore I believe we should prepare for the worst, especially in a home; but this is not limited to homes—it’s across the board. Unless an engineer specifies a current draw for a given load, electricians simply don’t size wire for the unknown loads. I have had people say to me to use the 3 VA that we use for calculations…..3 watts!?!


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[roger]

Sounds like a solution looking for a problem.

I have not personally encountered 10% VD ever, in a residential setting.

Power in my area is regularly 124-125 volts at the panel. I haven’t seen 120 in quite a while. Even 121-122 is getting uncommon.

AFCI breakers have questionable usefulness on a good day, so it’s not clear that a low voltage will make them function any less than they already don’t function.

 

[bsmale]

Sounds like a solution looking for a problem.

I have not personally encountered 10% VD ever, in a residential setting.

Power in my area is regularly 124-125 volts at the panel. I haven’t seen 120 in quite a while. Even 121-122 is getting uncommon.

AFCI breakers have questionable usefulness on a good day, so it’s not clear that a low voltage will make them function any less than they already don’t function.

Sir, it depends on the size of the home as to the length of the wires, so you may not have; but it is more than common.

As far as the power companies, yes, they are increasing voltage to account for the additional load and voltage drop on their end—I see the same voltages here. BUT, that does not change the fact that the manufacturers build their products within a certain spec, and we MUST abide by them. That would mean that a breaker that is rated at 120 with a tolerance of 3%, is only valid between 116.4 and 123.6. Regardless of how you feel about if they work or not, I personally have done tests regarding their functionality both in and out of spec—and they do their job while in. It truly doesn’t matter whether or not we like these breakers, they are required; and we should learn to work with them.


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[LarryFine]

BUT, that does not change the fact that the manufacturers build their products within a certain spec, and we MUST abide by them. That would mean that a breaker that is rated at 120 with a tolerance of 3%, is only valid between 116.4 and 123.6.

First of all, I have never heard of voltage regulation that tight from any utility.

Second, sometimes, we have to select equipment to suit the power as supplied.

 

[bsmale]

First of all, I have never heard of voltage regulation that tight from any utility.

Second, sometimes, we have to select equipment to suit the power as supplied.

Sir, I did not state that the power company regulates that voltage. All circuit breakers are rated at a particular voltage and tolerance. I know for certain, that Square D is rated at 120v. This is the tolerance of the breaker, and that is the voltage we must work within. I am not certain, but believe the other manufacturers fall within the same spec.


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[infinity]

Hello, and thank you for your response.

I disagree. Although it is a suggestion, it is one that should be followed. Arc-fault breakers have to be within their specs to function properly. It is in our Code that we are to follow manufacturer specifications, and this would be one of them.

Besides that, if you think it is ok to allow a voltage drop of up upwards of 10%, or more under load—it is not—

I have gone behind others and seen 101 volts under load, which did not allow the equipment to function; the voltage was simply out of spec.

My question still stands as my first post stated.

Again this is not a code issue it's a design parameter. If you want the cheapest installation possible you just do the code minimum. If this were a real world problem it would be addressed by the NEC.

A piece of equipment that won't work due to VD then the design would need to be changed. That is not the same as having a code requirement where you put the maximum load at the receptacle at the end of the circuit and test for voltage drop. I have heard of home inspectors doing just that and then reporting it as a defect which is wrong.

 

[bsmale]

Again this is not a code issue it's a design parameter. If you want the cheapest installation possible you just do the code minimum. If this were a real world problem it would be addressed by the NEC.

A piece of equipment that won't work due to VD then the design would need to be changed. That is not the same as having a code requirement where you put the maximum load at the receptacle at the end of the circuit and test for voltage drop. I have heard of home inspectors doing just that and then reporting it as a defect which is wrong.

It’s actually funny you mention that the code would address it….it somewhat starts to in 2023. The requirement for non-combination arc fault breaker and their respective receptacle is limited to right at 50 ft, which happens to be the approximate distance that VD comes into play. It is not addressed on combination circuits, but definitely on non.


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[don_resqcapt19]

Hello, and thank you for your response.

I disagree. Although it is a suggestion, it is one that should be followed. Arc-fault breakers have to be within their specs to function properly. It is in our Code that we are to follow manufacturer specifications, and this would be one of them.

Besides that, if you think it is ok to allow a voltage drop of up upwards of 10%, or more under load—it is not—

I have gone behind others and seen 101 volts under load, which did not allow the equipment to function; the voltage was simply out of spec.

My question still stands as my first post stated.

There was at least one attempt to put a mandatory voltage drop into the NEC for this very reason but it was rejected by the code making panel.
With more an more equipment in dwellings having switching power supplies with a very wide input voltage rating there is less of a reason to have a required voltage drop in the NEC. Even AC equipment often has a nameplate voltage range that would permit a 10% voltage drop.
This is a design issue and not a code or safety issue.

 

[don_resqcapt19]

Sir, it depends on the size of the home as to the length of the wires, so you may not have; but it is more than common.

As far as the power companies, yes, they are increasing voltage to account for the additional load and voltage drop on their end—I see the same voltages here. BUT, that does not change the fact that the manufacturers build their products within a certain spec, and we MUST abide by them. That would mean that a breaker that is rated at 120 with a tolerance of 3%, is only valid between 116.4 and 123.6. Regardless of how you feel about if they work or not, I personally have done tests regarding their functionality both in and out of spec—and they do their job while in. It truly doesn’t matter whether or not we like these breakers, they are required; and we should learn to work with them.


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I really doubt that you will find such a voltage requirement in UL 489, or UL 1699. I know for a fact that UL 943 requires GFCI to function at 85% of rated voltage.

If you believe this is a real world issue, you have plenty of time to write up a public input and solid technical substantiation for a new rule in the 2029 code. Public input submission will start in the fall of 2025 and end in the fall of 2026.

 

[LarryFine]

All circuit breakers are rated at a particular voltage and tolerance. I know for certain, that Square D is rated at 120v. This is the tolerance of the breaker, and that is the voltage we must work within.

If you're talking about standard breakers, the voltage rating is a maximum nominal rating.

Higher-voltage breakers may be used at lower voltages with no adjustments necessary.

I find it hard to believe that any AFCI or GFCI breaker will not function outside of 3%.

 

[bsmale]

If you're talking about standard breakers, the voltage rating is a maximum nominal rating.

Higher-voltage breakers may be used at lower voltages with no adjustments necessary.

I find it hard to believe that any AFCI or GFCI breaker will not function outside of 3%.

Yes sir, standard breakers. You will not find non standard in afci or gfci. And again, I did not state they will not function, but I know for certain I get nuisance trips. If I replace the breaker with a local device, which is rated at 125v, I don’t.


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[suemarkp]

As far as the power companies, yes, they are increasing voltage to account for the additional load and voltage drop on their end—I see the same voltages here. BUT, that does not change the fact that the manufacturers build their products within a certain spec, and we MUST abide by them. That would mean that a breaker that is rated at 120 with a tolerance of 3%, is only valid between 116.4 and 123.6. Regardless of how you feel about if they work or not, I personally have done tests regarding their functionality both in and out of spec—and they do their job while in. It truly doesn’t matter whether or not we like these breakers, they are required; and we should learn to work with them.

How does voltage drop at the end of a circuit affect the voltage applied to the breaker? Yes, there will be a small voltage drop in the service conductors to the panel, but that is more of an overall loading issue and not a branch circuit issue. Also a power company issue with the weenie conductors they use to feed a service, especially residential. I don't see how the breaker knows or cares whether the voltage has dropped 10V in the branch circuit wires and 110V in the load, or 1V in the branch circuit wires and 119V in the load.

 

[tallgirl]

First of all, I have never heard of voltage regulation that tight from any utility.

Second, sometimes, we have to select equipment to suit the power as supplied.

That's practically impossible. If you put a voltage monitor on a line you can watch large generation getting dispatched and turned off. I'd like to break into my neighbors house and do that and see what it looks like when my car is charging ...

 

[Steviechia2]

Power companies are increasing voltages on their lines to account for the increase in load, instead of fixing the cause of the problem.

Is this even possible? How would the power companies increase the voltage without changing all of the transformers?

 

[Fred B]

Power companies are increasing voltages on their lines to account for the increase in load, instead of fixing the cause of the problem

Is this even possible? How would the power companies increase the voltage without changing all of the transformers?

They do have voltage regulators on their systems that are to some extent adjustable with a variable regulator like this:

https://www.eaton.com/us/en-us/products/medium-voltage-power-distribution-control-systems/voltage-regulators/voltage-regulators--fundamentals-of-voltage-regulators.html

If a voltage is out of specs, the electrician can make a report, but that doesn't mean anything will be done as the variations are time of testing conditional and a lineman when finally getting on site to make an evaluation may or may not see the values the electrician witnessed and reported. The electricians ability to control an out of spec situation on the feeder or branch circuit level is very limited at best, and has no control over system of the POCO.

If OP is suggesting that the electrician takes some ownership of this beyond what is simple best case adjustment factors, then it would be forcing an extreme over sizing of conductor to mitigate a potential "possible" excessive VD. But then it could also start creating another issue related to AFC and SCCR of the local system breakers and equipment. Most residential panels used around here are rated to 10kAIC and more than a few appliances are only good to 3-5kAIC and the voltage drop aids in meeting within these limits. So eliminating ANY potential VD would now in concert with the POCO attempt to keep the levels stable, potentially make it necessary to increase the SCCR of the entire system installation.

One issue the POCO around here are complaining about is the amount of private PV introduced onto the POCO lines with spikes created by fluctuating sun/cloud causing spiking/lags faster than the POCO system can adjust to it. Regulations do say they must provide within a minimum tolerance the set voltages, and these spike and lags give them a real headache. And if such PV or other non-utility power generations are provided in the system after the POCO regulator, such spike/lags will be experienced to an even greater extent by neighboring properties.

regulatory requirement:
UNITED STATES DEPARTMENT OF AGRICULTURE RURAL UTILITIES SERVICE BULLETIN 1724D-114 RD-GD-2017-90 SUBJECT: Voltage Regulator Application on Rural Distribution Systems:

https://www.rd.usda.gov/sites/default/files/UEP_Bulletin_1724D-114.pdf