Wire Size

[ksmith]

I am in the process of correcting a PO's wiring. The shore power now has a breaker panel instead of direct runs to the recpts.

My question is from the gfi which is wired with 10/3 to the breaker panel would it be alright to use 12/3 down line to the next recpt? The breaker is 15 amp.

[Zednotzee]

Originally Posted by ksmith

The shore power now has a breaker panel instead of direct runs to the recpts.

Holy crap!!!

The 12 AWG is fine for a 15 amp circuit- as a matter of fact, that's what all the 15 amp circuits in your house are wired with. If you went to a 20 amp breaker I think you's need the 10 AWG.

[GordMay]

If I understand you correctly, you can reduce the wire size to #14AWG, from the 15A circuit breaker to any loads, including GFI Receptacles.

For a typical 30A 120V Shore Power System, #10AWG cable is required from the shore power receptacle, through the shore power cord, inlet, main disconnect and to the distribution panel. Branch circuits are sized according to anticipated load (but generally 15 Amp) which determines the breaker & branch cct wire size.

#10 AWG Cu wire is rated* 30A, #12 is 20A, and #14 is 15A.
*Ratings are per NEC, but ABYC Table VII (page 53) allows higher ratings, to which I do NOT ascribe, for AC wire.

See ABYC Section E-11, including the AC diagrams beginning at page 11.
➥ http://www.abycinc.org/committees/e-11.pdf

[Tellie]

Though you can use 14 AWG for a 15amp circuit, I personally would perfer the 12 AWG on a boat. Add a little corrosion at the terminals over time and a nicked trim and you can effectivly reduce a 14 AWG to a 16 AWG pretty easy.

[ksmith]

Thanks guys. Don't think I would go below 12ga on the 110ac. Got a really good buy at Home Depot on some 10/3 marine grade they were closing out figured for this application heavier would not hurt. Just wondering in case I run out.

Nah the holy crap was the wire nuts for the bilge pump in the bilge.
The things people do to boats amazes me.

[Tellie]

Wow I didn't know Home Depot carried marine grade wire. I'm gonna have to look closer next time I'm in there.

[Cheechako]

I believe 14ga is std in houses for 15 amp....? so nothing wrong with 12ga.

[ksmith]

Tellie:

I don't think they carry it anymore. I got mine locally as they were no longer going to carry it. It was Ancor and I bought 3 spools of 25ft for about $40.00.

[Rene]

ksmith; As a retired electrician the best advise for anyone contemplating boat wiring, is get a book. One of the best I know is by NIgel Calder. It is specific to boats and has most all tables for AC and DC wire sizing (they are not the same ). The reasons for different ampacities for the same wire gauge can be attributed to the type of insulation and / or weather your dealing with wire (1 conductor) or cable ( more than 1 conductor). Be safe.