# Thread: Voltage Drop Information / Articles

1. ## Voltage Drop Information / Articles

I am looking for any information and/or articles you astute gentlemen may have laying around in files or folders pertaining to 'Voltage Drop' to add to my reports.
More so for 15/20 amp Circuits.

Much Thanks in advance.
Robert Young

2. ## Re: Voltage Drop Information / Articles

Robert, are you looking for code related stuff or for a way to calculate things?

I suspect that getting into this area of things is going to be like uncovering an undocumented septic system. The after effects just never seem to quit showing up.

Anyway, the Mike Holt site has some "freebees" which include a voltage drop calculator.

I've started purging my main computers of a lot of web stuff that gives easy answers to a lot of things because I retired (mostly). I haven't deleted it all, but the backup drives aren't in the machines right now. I'm sure, though, that if you get on something like Dogpile and enter a search phrase like voltage drop calculator and voltage drop rules you can stay busy for an evening sorting all the toys out.

Last edited by Bill Kriegh; 09-25-2018 at 03:00 PM.

3. ## Re: Voltage Drop Information / Articles

Evening Bill. Thanks for chiming in.

As per NEC code and Mike Holt, I review both.
1. Branch Circuits – This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%.

Bill, I had an article, to which I misplaced, and to whom I forgot penned the article, that I back-ended in my electrical reports concerning 15 amp circuit receptacle dV, that explained, and do not quote me on this, adverse operations from electrical equipment can be directly correlated to dV measured at 8.3% and higher on 15 amp 120 V branch circuits.
This is the type of article I am looking for.

I inspected new construction were >80% of the receptacles, and I analyse every receptacle, displayed between ><6% to >19% dV.
The receptacle closed the dist
ributional panel measured ><2%. Normal in my view.
I was truly amazed. I hypothesized, long receptacle circuit runs, too many receptacles and to small AWG for those circuits. Impedance related voltage drop by not doing proper receptacle and AWG calculation.
We are talking about a \$500,000-1/2 million dollar home.

Looking forward to others chiming in.

Best regards.
Robert

4. ## Re: Voltage Drop Information / Articles

Robert,

The FPNs in the NEC have gone away, now being "Informational Note" instead.

The difference? What does Fine Print typically indicate, and FPN was for Fine Print Note.

I believe it was in New Jersey that a lawsuit was won which made FPN enforceable within the jurisdiction of that courts circuit/district - NFPA took note of the court's decision and renamed the notes to "Informational Note" ... they are no longer "fine print" ...

This is the way I addressed voltage drop - check the farthest away receptacle outlet on each circuit (which takes some guessing as you don't know how the electrician ran the wiring, but the farthest away receptacles are, typically, the longest runs).

If they test high voltage drop (greater than 10%), it's worth writing up. If you get ~10% at receptacle outlets which are not too far away from the panel, those are worth writing up.

What you will likely find is: enter a room and measure the first receptacle outlet, then the next and the next and the next - if you find what I typically found, each one measures randomly high (no rhyme or reason for the variation in Vd ... no reason other than the receptacle outlets are wired backstabbed instead of under screw terminals ... it is those backstab connections which create the Vd readings because so many are poor connections, and they are within the receptacles themselves (can't blame that contact on the electrician ... other than they used the back stab terminals instead of the screw terminals - that IS their fault).

If per chance you measure a Vd at the closest receptacle and a slightly higher Vd at each next receptacle, the receptacle outlets are likely wired using the screw terminals and you are actually measuring the Vd of the circuit, and each length of wire adds to the Vd.

As I recall, 62-1/2 feet of circuit length (that's 125 feet of conductor: 62-1/2 feet out and 62-1/2 feet back) gives ~5% voltage drop at 15 amp on 14 AWG copper (I did the calculations decades ago, that is from memory).

If you measure 10%, that's not good.

Some will argue that "No circuit is designed to carry 15 amp all the time, so voltage drop is no big deal.", and while that is basically true ... there is a 15 amp breaker on that circuit will WILL ALLOW THAT TO HAPPEN ... so much for the "so voltage drop is no big deal" regarding that particular reasoning.

Many appliances, especially electronics, and what appliances do not have electronics in them nowadays, are rated for 120 volts +/- 10% ... there is that "10%" I referred to.

The best solution to Vd that I found was to convince as many contractors as possible that they could solve 90% of their Vd issues with inspectors and owners by doing one simple step: use 12 AWG for all 15 amp circuits as well as 20 amp circuits ... the reason is that backstab terminals for devices no longer accept 12 AWG, only 14 AWG, so unless the electrician wants spend the time to scrape off enough copper to make the 12 AWG fit in (I have seen that done), they will use the screw terminals - and their Vd issues disappear (on all but their long runs, and up sizing to 12 AWG (a 200 foot circuit run of 12 AWG will give about 9% Vd at 15 amps).

How to solve Vd issues? Use 12 AWG for 15 amp circuits - even in larger houses (get a 200 foot circuit length for less than 10% Vd) ... unless you want less than 5% Vd, then you would need ... 8 AWG!

5. ## Re: Voltage Drop Information / Articles

"The FPNs in the NEC have gone away, now being "Informational Note" instead."
Thank you. Good information.

When I enter a room, I follow a circuit voltage/drop up and downstream. Vd is the indicator, as you know.
I typically/usually write up Vd exceeding 8.2V but may note Vd is the abundance of receptacles exceed 5% Vd.

"Many appliances, especially electronics, and what appliances do not have electronics in them nowadays, are rated for 120 volts +/- 10% ... there is that "10%" I referred to."

120-10%Vd is 108 V average.

Thanks. I will try to find the article I am referring to on my previous post.

6. ## Re: Voltage Drop Information / Articles

Originally Posted by ROBERT YOUNG
[When I enter a room, I follow a circuit voltage/drop up and downstream. Vd is the indicator, as you know.
Given a continuous and uninterrupted conductor, that would be correct.

With consideration given to a conductor which is discontinuous and is interrupted by connections (at devices splices, and outlet tap points), that no longer holds true.

It is not uncommon to find voltage drop vary greatly when going around a room.

And, typically the cause of that is backstabbed connections into devices ... unless the use of such devices is not allowed north of the border?

7. ## Re: Voltage Drop Information / Articles

Originally Posted by ROBERT YOUNG
I am looking for any information and/or articles you astute gentlemen may have laying around in files or folders pertaining to 'Voltage Drop' to add to my reports.
More so for 15/20 amp Circuits.

Much Thanks in advance.
Robert Young
curious as to what testing equipment is being used to determine Vd?

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