On Sun, 27 Sep 2015 21:42:02 -0700 (PDT), Uncle Monster
wrote:

On Sunday, September 27, 2015 at 10:10:58 PM UTC-5, Seymore4Head wrote:
On Sun, 27 Sep 2015 19:56:38 -0700 (PDT), Uncle Monster
wrote:

On Sunday, September 27, 2015 at 8:31:46 PM UTC-5, wrote:
Hi. I'm laying out my basement lighting. I expect to have 25 recessed lights, each is 75watt max rating (even though I will use LED, I know I must still assume max rating of fixture). 25x75=1875watts/120V = 15.6amps.
So, I cannot use one 15amp breaker and 14awg wire.
Can I wire all the lights with 12awg and a 20amp breaker?
All comments appreciated.

Thanks
Theodore

The breaker is there to protect the wiring. I you're really worried about overloading the circuit, you can feed the switch with #12 then split the lights into two strings wired with #14. One with 12 and the other 13 light fixtures with the circuits joined to the hot and neutral in the switch box. You'd need to use a deep switch box to make sure there's enough room for the wiring. ^_^

[8~{} Uncle Smart Monster

You are not supposed to use #14 at all if you have a 20A breaker.

You're right but I've never seen a 20 amp breaker not trip when a #14 wire was connected to it and shorted. I haven't read the code on it but there is a guy who posts here in the group who is/was an electrical inspector. The #18 wire in a light fixture is tied to 20 amp circuits all the time. The #14 circuits could probably allowed because there is little or no chance of 20 amps being on a lighting circuit unless you were to screw resistance heater elements into all the light sockets. A 20 amp AFCI breaker would protect the circuit much better. ^_^

[8~{} Uncle Doubting Monster


That is the idiot clause. (240.4(D)) that says unless otherwise
permitted in the code 14 ga wire shall be protected by a 15a breaker.
(12=20, 10=30)
It forces the 80% rule on "small conductors"

I could tell you where it is otherwise permitted but your head might
explode (like a legal 40a breaker on 14ga wire)


When you start talking about "fixture wire" (your 18 ga example)
that has to be part of a "listed" assembly, typically U/L listing.
Typically 18 ga wire has a design ampacity of 7a but in a listed
assembly where the load is controlled it can be protected by a 20a
breaker.
You are dealing with 2 issues, "overload" and "short circuit"
protection.
An overload is simply having too much load on the wire. Short circuit
protection is a bolted fault where there is essentially no limit to
the current but the resistance of the wire and the breaker, An 18 ga
wire, less than 50 feet long will operate a 20 a breaker in a bolted
fault.

At least that is the thinking.

You can still get in plenty of trouble with extension cords but we
were talking about lamps.