subpanel circuit breaker

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  #1  
Old 03-31-04, 11:17 AM
bpotter
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subpanel circuit breaker

I had someone suggest that I should have a 60A CB at the main panel AND a 60A CB (with lock-out) in my subpanel (in detached garage). How would that work? Don't my hot wires go to the lugs on the subpanel? How would a 60A CB in the subpanel help me? The subpanel has space for 6 circuits (I'm only using 4). Right now my hots feed the panel, which feeds the CB's. I already have established that I don't need a disconnect at the subpanel since it only has room for 6 circuits. Does this guy know what he's talking about, are is he giving me bad advice?

Thanks.

BCP
 
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  #2  
Old 03-31-04, 12:25 PM
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You need the circuit breaker upstream to protect the feeder. At the subpanel, the breaker would only provide a main disconnect. Since you don't need the disconnect, you don't need the breaker.
 
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Old 04-01-04, 11:41 AM
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I would modify John's response slightly.

The circuit breaker in the subpanel would not be _required by code_. If you _want_ to have a single main disconnect in this sub panel, you _could_ do that.

The 60A breaker in the subpanel would 'help' you in that if you wanted to quickly turn off all of the power in that panel, you could do it with a single 'throw of the hand'. IMHO, not really worth it.

If the subpanel had more than 6 breakers in it, then code would require the use of a main disconnect at the subpanel. One standard way of doing this is by 'backfeeding' a circuit breaker.

There are specific code rules for 'backfeeding' circuit breakers, where the power comes _in_ from the breaker terminals and goes to the bus stabs. The specific breaker that you are using has to be listed for this application, and will probably require a hold down kit.

-Jon
 
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Old 04-01-04, 12:37 PM
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Winnie,

Your comment....
"If the subpanel had more than 6 breakers in it, then code would require the use of a main disconnect at the subpanel. One standard way of doing this is by 'backfeeding' a circuit breaker. "

what do you mean by backfeeding a circuit breaker?? I am installing a subpanel with a 100a breaker in my main panel and no 100a breaker in my sub panel. Is that considered "backfeeding" a circuit breaker?

Thanks,

Lou
 
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Old 04-01-04, 12:49 PM
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'Backfeeding' a circuit breaker is where you supply power _to_ that circuit breaker through the terminals that you normally connect the load wires to.

What you are doing is _not_ backfeeding a breaker. You are using a 'lugs only' panel as a subpanel. If you wanted to install a main breaker in this 'lugs only' subpanel, then one technique that you _might_ be able to use is to install an ordinary breaker, and then 'backfeed' it as the main. This may be done if the equipment is correctly designed and listed for the application.

Your subpanel doesn't need a main disconnect because it is in the same building. The above discussion applies to a panel in a detached garage.

-Jon
 
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Old 04-01-04, 01:05 PM
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thanks for the information winnie. You had me scred for a split second there.

Lou
 
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