15 Amp vs. 20 Amp Circuits


Old 01-31-02, 07:53 PM
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15 Amp vs. 20 Amp Circuits

Is there any particular reason not to go with 20 amp circuits for general lighting and receptacles throughout a dwelling?
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Old 01-31-02, 08:00 PM
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I don't think so.

Although there are those that will point out that 15-amp circuits are safer than 20-amp circuits. And of course they are right, but to me the flexibility of 20-amp circuits is worth the small difference in safety. And apparently the NEC doesn't think the difference is significant either, since they allow either.
Old 01-31-02, 08:56 PM
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Safer in regards to electrocution or fire? Is it really that much more dangerous? I agree with you, I would rather have the additional capacity of a 20 amp circuit. However, in most books I've seen they specify 20 amps only for the kitchen and laundry receptacles and 15 for all the others.
Old 02-01-02, 07:00 AM
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I don't see any safety benifit from a 15 amp vs 20 amp circuit, as long as you use the correct wire size. Death occurs at .01-.02 amps.
Old 02-01-02, 07:35 AM
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In new construction, our local county code does not allow for any 15 amp breakers (No breakers under 20 amp)or any wire gauge smaller then 12 gauge (No 14 awg allowed).
Even though NEC allows for it, I suggest checking with local inspectors to see if they follow the NEC or if they have their own extra rules governing this as mine did.
So when asked if there is any particular reason not to go with 20 amp circuits, I would have to answer that that is my only choice!
Old 02-01-02, 08:51 AM
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We're only talking about a fire danger here. 15 amp and 20 amp circuits have more than enough power to kill you easily.

The theory is that if a lighting fixture malfunctions, say it starts to draw 18 amps instead of whatever it's supposed to, then the fixture might catch on fire. My guess is that NEC and UL experience has shown that malfunctions of this type are extremely rare, and hence does allow lighting on 20-amp circuits.

As has been said, there is a growing trend in the U.S. to 20-amp circuits and 12-gauge wire. But I note that 20-amp circuits are very rare in Canada. In Canada, even kitchen counters are wired with only 15-amp circuits (although they require six 15-amp counter circuits where the U.S. requires only two 20-amp circuits). Canadian electricians think all our 20-amp circuits are weird.
Old 02-03-02, 09:34 AM
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Using #14 for your lighting fixture circuits where you are more in control over the circuit loads will give you a much easier time folding the conductors neatly back into boxes. For receptacle circuits with unknown things being plugged in #12 is the only way to go. Where you may use dimmers you can also compensate by using deeper boxes. Bigger boxes and underloaded circuits give more options for adding conductors, timers, dimmers, etc.
Old 02-03-02, 11:39 AM
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IMHO I believe it is more important to calculate the load of each circuit.

Side note. I never have half a bedroom one one circuit and half on other. (Not a code violation). But a common practice here.

I am also afraid when AFCI's are required (AHJ) that some electricians will put one AFCI breaker to serve all the bedrooms. Like they use to do all bathrooms, basement, garage,front and back door outlets on one GFCI circuit.

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