Branch Circuits

louis bugaj

What are the maximum run (in feet) on 15 A using #14 Awg and 20 A using #12 AWG branch circuits from the main breaker in residential?
General rule is 5% voltage drop from utility company drop. But I can not find anything in black and white in Article 310.
Any body has any information, I'm surely appreciated.

Thanks,
Louis

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Louis Bugaj

mdshunk

The code does not provide any minimum or maximum voltage drops. That's a design issue and not a safety issue.

The rule of thumb is 3%.

For a fully loaded 15a, 120 volt circuit with #14 wire, your max run at 3% drop is 45 feet. at 240 volts, 90 feet.
For a fully loaded 20a, 120 volt circuit with #12 wire, your max run at 3% drop is 55 feet. at 240 volts, 110 feet.

louis bugaj

Thank you MD. I wonder how the highend houses passed the inspection.

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Louis Bugaj

Speedy Petey

Like marc said, it is not a code issue so there is nothing to fail.

Also, remember the numbers Marc gave you are fully loaded circuits. No circuit should ever be fully loaded, except for maybe for a short time. This is because there are so many circuits in a home, and anything heavily loaded is usually accounted for.

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firemike

Petey is correct, a circuit should be loaded to more than 80% or it's rated capacity- 15 amp circuit...12 amps max and a 20amp circuit... 16 amps max

mdshunk

While that's certainly a good idea, the codes permits a circuit in a dwelling to be loaded 100%, unless it's for electric heating. For commercial, the 80% rule applies.

747

Is there a big difference in being a commercial electrician and a residental. Because if i was a electrician like you guys i think it would be awesome to work on a electric crew that was wiring a brand new skyscrapper in chicago. So i guess my question is this. Could you guys get a job on a electric crew building a new skyscrapper and know what your doing or is that a completely different ballgame then residental.

Bob Kovacs

The theory is the same, the application is different. A lot depends on your training. If you became an "electrician" by nailing up boxes where someone told you to, pulling lots of Romex to boxes and learning how to install an outlet properly, you're still a long way from being able to do commercial work. If you've got through a formal apprenticeship program, you've got a better grip on theory (the reasons "why" you're doing what needs to be done), as well as the hands-on training with conduit, pulling feeders, etc.

In general, commercial work is a lot more involved than residential- especially when you bring up the skyscraper example. Ever seen the switchgear in a 50-story building? Quite a bit different than your 100A panel at home

Bob

Bkessler

Hey MD are saying a fixed appliance or dedicated circuit can be loaded 100% in residential. I know lighting circuit can be and general purpose outlets it's hard to say because of the variable's of whats being plugged in. bk

mdshunk

Fixed electric space heating appliances may only be loaded 80% in a dwelling. Everything else in a dwelling is considered a noncontinuous load, and may be loaded 100%. See art. 100, definition of continuous load. I should hedge by saying that there might be some load types in certain homes that do meet the definition of a continuous load, that could only be loaded 80%. I'm thinking of a swimming pool filter pump off the top of my head right now. Mostly, you'll only load that circuit no more than 80% anyhow, so that the motor won't nuisance trip the breaker.