On Monday, September 28, 2015 at 12:42:09 AM UTC-4, 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.

A direct short is only one failure mode that a breaker protects against
and it happens so quickly that the wire doesn't get a chance to overheat
so an undersized conductor would easily pass that. The other failure is
an overload, which will heat up the wire continuously over a long period.
Even there, considerable margin is in the code, so in most cases, a 14
conductor on a 20 breaker isn't going to start a fire. But the code margin
is there for a reason and most cases don't matter if you happen to have
the one that does.


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