Hi All; I usually hang out in Knots, but I have a wiring question.
The subpanel for my shop is powered by 8 guage copper wire,(aprox. 50 ft.), and a 40 amp. breaker from the main panel. Can I run a 60 amp. breaker on this guage wire?
I was looking at the AWG table on their website, and it states
(8 guage- max. amps. for chasis wiring 73)
(8 guage- max. amps. for power transmission 24)
I’m a little confused. I’m a little confused. Any help would be appreciated.
Thanks. Walker1
Replies
Hi,
My sources say that with a two-wire copper 8-gauge supply to a subpanel you have a max capacity of 30 amps.
D.
No, at 40 Amps, you already have the correct maximum breaker for wire rated at 60 degrees centigrade. If the wire is rated for 75 centigrade, you can go up to 50 amps, or for 90 centigrade to 55 amps. But 60 is too much.
-- J.S.
Re: "for 90 centigrade to 55 amps"IMHO you could go to 60A for 90C wire as there are not 55A breakers so the next larger size would be 60A. Of course none of this applies because most breakers are only rated for 75C so even if the insulation were rated for 90C you would have to fuse it at the 75C rating of the breaker. Of course the additional capacity provided by the 90C insulation above the 75C rating could be used to advantage when calculating fill and ambient temperature derating.
What is the 8 awg copper in? A raceway or a cable? If it is in a NM, NMB, or NM-2 cable then it has a maximum allowable ampacity of 40 amps. If it is in a raceway then replace the 50 feet of wire with 6 awg or 4 awg.
How old is the original installation?
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