Wiring Guide - Looking for further confirmation

Old 01-04-05, 09:07 PM
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Question Wiring Guide - Looking for further confirmation

I'm located in Iowa and finishing my basement. This is my 3rd basement project so I have some prior experience with wiring, but I'm by no means an expert . I was looking through my wiring guide book in preparation for wiring the lights and outlets. I typically wire lights with No. 14-2 (with 15 amp breaker) and outlets with No. 12-2 (with 20 amp breaker). I believe 14-2 is sufficient for lighting and is easier wiring to work with and I like the heavy 12-2 wiring for outlets and potential heavier loads.

My book says the following info:
Wire Size - Amps - Watts (based on 120 volts at 80% loaded)

No. 14 wire - 15 amps - 1800 watts
No. 12 wire - 20 amps - 2400 watts

Does the above from my wiring book make sense? Do others agree?

I would also really like other resources that would help determine things like: 1) what's the maximum number of outlets that should be connected in 1 circuit? 2) does total length/feet of wiring make a difference? 3) and other things like this that give general guidance to proper wiring.

Thanks in advance for any assistance or links to other web sites.
Old 01-04-05, 09:14 PM
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The numbers you quoted (1800 watts and 2400 watts) are what is available at 100% load, not 80% load. If you want to limit yourself to 80%, then the numbers are 1440 watts and 1920 watts. Limiting yourself to 80% is a good idea but not generally required.

As to your questions:

(1) In most parts of the U.S., there is no limit of receptacles on a circuit. But the standard rule of thumb is no more than 8 on a 15-amp circuit or 10 on a 20-amp circuit. You'd be wise to use fewer in areas where you know there will be a lot of electrical stuff, and you can use more (but I woundn't particularly advise it) in areas where you know there will be little electrical usage.

(2) The longer the run, the more the voltage drop. Up to about 70 feet from the panel, it's not too important.

(3) Books are the best general guidance you can get. Read lots of them.

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