House wiring question FAQ

Here, the gauge applies to the entire run after a breaker, because any socket can demand the total current (the breaker will not break till the demand is greater).

That is what I thought too. Thank you for the double check

There can be smaller wire downstream, but that is not common. If #12 wire is on a 15A breaker I would wonder.

It is not terribly out of the ordinary to have long runs from the panel to loads at the far end of the building to have an "oversized" feed run - particularly for "load" circuits - kitchen (small appliance) bathroom (hair driers / heat lamps etc) or home office (laser printers?) or home entertainment rooms. At least here in Ontario where my father was an electrician (back in the days before the days lf LED lamps it could be a high wattage lighting circuit)

Hi Clare,

If I find the wire a sufficient gauge (same as the 20A legs) at the panel to handle a 20A breaker, is there any reason to stay with the 15A and not upgrade?

-T

Are you tripping the breaker ? If not , why "upgrade" ? If you're adding a load that draws more amps than the current breaker can handle I can see it but otherwise I'd probably say no . And if you're adding a load that big it should probably have a dedicated circuit .

Since I got my new panel with my new whole house generator, I have been getting "nuisance trips" on my four circuits with 15 amp breakers. It is the four circuits with my refrigerators, air conditions, and microwave oven on them.

Schneider discontinued HOM115HM (high magnetic) breakers, which would have solved the problem. They only have HOM120HM breakers. They would solve the issue, but only if my wiring will take it.

I did not have any issues with my old breakers.

And, of course, if a clueless homeowner has been meddling with the wiring, anything can happen. I once owned a house that used zip cord for some of the wiring in the attic, laying on top of the joists.

I put loads that big on 20 amp breakers with 12 ga wire . The only 15 amp circuits I installed when I wired this place were for lighting and those circuits got 14 ga wire .

Now if I can only get my electrician to come and check!

I knew a man who had a house built in Florida. He said the contractor used #10 wire throughout. I'm not sure what his reason was.

Bill

My brother bought a house that was built during WWII. When He rewired he found a length of zip cord in it. Of course during the war all building materials were tight. So some people made do with whatever they could find. Especially since we had a housing shortage during the war.

Bill

That is kind of hard to believe as it wold be very difficult to put # 10 around most receptical screws unless they used smaller wire in the box between the # 10 and the recepticals. Maybe they used the aluminum wire as it needs to be a few sizes larger than the copper wire..

I beg to differ. There is no issue using #10 with standard duplex (or simplex) outlets[*] and switches. It's even common for long

I know someone who had a house fire about 15 years ago. The cause seemed to be zip cord used (probably by a previous owner) to install lights around the bathroom mirror.

He checked and the wiring is the same on the 20 amp and 15 amp circuits. He is in the process of order out HOM120HM breakers.