No I'm not, you are trying to make a one size fits all. I would take the known or anticipated load and the information Don asked for in post #15 then use that.
Voltage drop
- Thread starter Therealcrt
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You can do nothing, just use #12 conductors and it's code compliant. Or you can do the VD calculation but you will need to decide what the current at the end of the circuit is. For a 20 amp circuit you can use any number that you can pull out of the air because without knowing the load you're just making a guess. Worst case scenario use 20 amps. If you know that they're plugging in a 10 amp toaster use 10 amps.
Therealcrt
Senior Member
- Location
- Kansas City
- Occupation
- Electrician
OK so it’s co-compliant to use number 12 conductors 500 feet away and the voltage only being 80 V when the load is connected because you installed the device not knowing what load would be installed that might be code compliant but it’s downright stupid so why is it not in the code?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Therealcrt
Senior Member
- Location
- Kansas City
- Occupation
- Electrician
Ok so back to the video then, what is he really saying then
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Mike's point from the portion of the video I watched is that the NEC does not require voltage drop compensation (there are a few exceptions). But when you read 110.3(B) that section would require you to follow the manufacturer's installation instructions and if the equipment is built to ANSI standards then you have to follow their (ANSI) recommendation of no less than 10% below nominal and 5% above nominal voltage at the equipment.
- Location
- Illinois
- Occupation
- retired electrician
The system for public inputs to make changes for the 2029 code will likely open in the 4th quarter of this year and close in September of 2026, so you have plenty of time to write up a code change.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
How much voltage drop would be tolerable is your or your your customer's decision; aside from the examples Don mentioned there is nothing in the NEC that says 3% or any other number is max for Vd.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
If the device at the end of the conductor run operates just fine at 80V, then what's the problem?
And, those two don't always intersect at the same point!
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
How can you possibly know that without a known load?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
You would have to be very careful with the wording of any voltage drop requirement. Take your example, if it's just running a Wi-Fi router then it is totally fine in sizing for the full 20 amps would be a complete waste. This is the problem we see in a lot of energy codes that have voltage drop requirements and they are quite vague so in most people just assume it's the full rating of the branch circuit or feeder. This is typically very wasteful. Also maybe you want a lot of voltage drop for fault current reduction purposes, or to reduce the wattage of a resistive load, or has been mentioned maybe the load is totally fine with a large voltage drop.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
It shouldn't be a requirement and it isn't because unless there is a specific load involved it cannot be calculated unless the NEC is going to give you a parameter to use like for a 20 amp circuit assume 16 amps in the VD calculation. Something that isn't variable like a fire pump is simple. 500' away, 150 amp load, copper, done.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
Probably because you're all over the place. They've answered each of your questions the six different ways you've asked it.
Then make your own conclusion. Worried about it? Do some math or don't do some math; use a rule of thumb; see what is inside the back of the van to use; do as you please unless you are installing a circuit for a fire pump or sensitive electronic equipment, as Don mentioned. There's no right answer, it's entirely up to you as the designer of the circuit. There's been occasions I've used 1A as my load for the math, and other times I've used 20A, it depends on your opinion of the conditions and what they want to pay for.
(Edit to add: getting back into the swing of things and made the rookie mistake of not noticing there was a page two, whoops!)
- Location
- Illinois
- Occupation
- retired electrician
If the code does not address it, it becomes a design issue. There are very few cases where the code addresses voltage drop.
I'd go by the ANSI or your state energy code whichever applies,
It says your in Kansas
and the nice folks here all telling you voltage drop is not 'in the code' do not know all the adopted codes in Kansas.
Voltage drop is not in the NEC because just like the code on smoke detector placement, its out of the scope of the NEC to cover the topic,
but wait its not out of the scope the 2018 energy code as adopted by many if not most states, such as NY, NJ, IL, FL and your state of Kansas:
Which states:
They will all now pile on and say oh but its not enforced, but its in your state code and if your required by a contract to meet all applicable codes then there is your answer.
I think its misleading for a well known educator like Mike to overlook this fact, its like saying the NEC does not require residential smoke detectors so forget about them.
Therealcrt
Senior Member
- Location
- Kansas City
- Occupation
- Electrician
Finally a good response
ptonsparky
Tom
- Occupation
- EC - retired
I hadn’t noticed an energy code mentioned in the OP.
Nope, still don’t.
Nope, still don’t.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Ok but it doesnt say what current to use. I will use my own judgment and will NOT be using the OCPD size of the branch circuit or feeder.
The inspector that dinged me (not that long ago) said I could use any method I wanted, as long as it was reasonable. I tried everything, just going off the nameplate (motor in my case) I was not even in the ballpark of compliance.
woopsy.
First time we got dinged on voltage drop I hadn't either, as I had never been trained on it. My apprenticeship days were long before an energy code.
It cost the boss a lot of wasted time and money.
I am not saying I agree or disagree with the law, but just do a good job and do know the law that governs you. It should be included in Mikes training IMO.