Adding a sub panel to garage

[transferguy]

posted by: hawkertech

I have a newer 100A service panel and am planing on running 6/3 copper about 60 feet to a small sub panel in my attached garage to add circuits there so I don't have to make several long 12/2, 10/2 runs to add what I want there. Yes I know most service panels are installed in the garage but mine is in the basement at the other end of the house which was built in 62. I plan on feeding it with a double 50A breaker but I have heard from some people on other forums that I can feed it with a 60A breaker. This does not seem right to me since 6awg is rated for 55A. Am I correct is saying that you can not use a double 60A breaker on 6/3 wire for 220V?

[transferguy]

posted by: suemarkp

If the calculated load for the subpanel is 55A or less, then you are allowed to "round up" to a 60A circuit breaker because 55A is not a standard breaker value. You can't apply this round up rule to multi-out branch circuits, but can on feeders under 800 amps. There are other exceptions that would allow an even larger breaker (e.g. a welder or large motor or compressor being fed by that panel).

Seeing how many homes get wiring modified by handymen who don't know what they're doing (and don't do load calc), you'd be wise to limit yourself to the 50A breaker even though code will most likely allow it. You never know what a future homeowner will add...

Mark
Kent, WA

[transferguy]

posted by: hawkertech

Posted by suemarkp

If the calculated load for the subpanel is 55A or less, then you are allowed to "round up" to a 60A circuit breaker because 55A is not a standard breaker value. You can't apply this round up rule to multi-out branch circuits, but can on feeders under 800 amps. There are other exceptions that would allow an even larger breaker (e.g. a welder or large motor or compressor being fed by that panel).

Seeing how many homes get wiring modified by handymen who don't know what they're doing (and don't do load calc), you'd be wise to limit yourself to the 50A breaker even though code will most likely allow it. You never know what a future homeowner will add...

Thanks for the help Mark. I just plan on adding a 20A circuit for outlets for general use and powered hand tools, a 30A RV outlet and maybe some more garage and exterior lighting powered by the sub panel. I will stick with a 50A breaker.

[transferguy]

posted by: suemarkp

OPosted by hawkertech

Thanks for the help Mark. I just plan on adding a 20A circuit for outlets for general use and powered hand tools, a 30A RV outlet and maybe some more garage and exterior lighting powered by the sub panel. I will stick with a 50A breaker.

Even a 30A circuit would work in this case -- RV on one leg and the lights/outlets on the other. So a 50A will provide plenty of growth.

Mark
Kent, WA