ECN Forum Forums General Topics of the Trade General Discussion Area 14-2 on 20 amp circuit

The wire size corresponds with the breaker size, not the load.

Dave

Dave, this is and is not the case.(that made alot of sense didn't it? )

Actually in many cases the conductor is sized for the load and then the OCPD is sized to this.

Now, with out doing any math at the moment, (so don't hold me to the actual numbers)
let's look at article 430 for example.

With the applicable parts of this article we could possibly have a # 12 connected to a 45 amp breaker.

The conductor is sized for the load, the OCPD is sized to carry and start the load, and is for short circuit protection.

The OL's are actually the conductor and equipment protection here.

Of course this is not the situation or discussion in this thread.

Roger



[This message has been edited by Roger (edited 05-05-2004).]

You're so right, Roger. I'll have to do a little studying on the impedence of the combined contributors of a MOTOR switch leg. Can you help me find the table for the voltage required to beat a dead horse?

I was actually thinking of a job I bid on recently that illustrates the problem with using smaller wire for the switched pair, other than the obvious violation. In a very nice neighborhood, the homeowner had built a 3-season room. The exterior light (now in the 3-season room) had an outlet as part of the fixture. Someone other than an electrician wired the room entirely with NM, which then came out of the ceiling and was connected to a plug...into this light fixture. It included six outlets, a ceiling fan, and three exterior lights. There was another NM cord plugged into a non-GFCI exterior outlet for a TV outlet. Of course there was no WWIU cover.

Dave

I figure this string might be good for yet another posting or two.

At the simplest level, the primary function of the branch circuit breaker is to protect the downstream wiring. In order to do so, the wire must have equal or greater capacity compared to the circuit breaker.

So, the questions are:
1) Will the #14 wire be adequate for the purpose Randy has intended? Absolutely, but . . .
2) Will the #14 wire be adequately protected by a 20 amp CB, according to the NEC? Absolutely not.

It's all about protecting the wiring, not matching the wire as closely as possible to a small load. That's why we can't wire lighting circuits with 18 gage wire.

Thanks,
Radar

That's what I thought the code wants. That if one problem happens (overcurrent due to a fault) you don't cascade to a bigger problem (house fire). Because the breaker kicks out.