Xknob&Tube

When does a residential sub-panel need a main breaker? I'm thinking for a detached garage/shop/etc? But I can't find it in the code. Any help is appreciated...

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480sparky

225.31.

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nitro71

You have to have a main if the sub panel is in another building. If it's in the same building the main that feeds it is sufficient.

Dennis Alwon

What article states that. Article 225.33 allows six breakers max for the disconnecting means.

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raider1

You could also use a separate disconnect at the separate structure insteas of a main or 6 breakers in the panel.

Chris

amptech

He said residential, so lets suppose he's talking about a 200A main breaker panel and he is going to install a 60A or 100A 2 pole breaker to feed this sub panel in the same building. He still has only one main(the 200A CB) that disconnects everything. He could install (6) 2 pole 60A in the main panel and feed (6) sub panels in the same structure and as long as the panel has a main breaker that kills everything he is code compliant.

Dennis Alwon

I don't know what you are trying to say. He stated a detached garage. I am saying that you never need a main breaker in a sub panel, detached or not. At a detached structure you can have a main breaker, main disconnect or you can use the 6 handle rule. If the sub panel is in the same building then the sub panel doesn't need a main breaker but of course it need to be protected by a breaker just not at the panel. That would not be a main breaker.

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Xknob&Tube

It's a sub-panel in a barn about 100' from the house.

A few months ago I had a similar thing - a 100 amp sub-panel in a detached shop and the home-owner supplied the panel and it had a main breaker. When the inspector came he said "just checking to see if the panel has a main breaker". I said "I didn't think a sub-panel had to have a main". The inspector said "if it's detached it does". I said "Whoa - I didn't know that!"
I know that I installed one a few years ago without a MB and it passed...

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480sparky

Didja ask for a Code reference?

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In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

Speedy Petey

Doesn't mean it's right.


A "main breaker" is not required. That is simply one form of disconnect that can be used for the structure. It is also the easiest.

II. More Than One Building or Other Structure
225.31 Disconnecting Means.
Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.

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Dennis Alwon

Sometimes I think terminology gets everyone. I remember saying the panel needed a main but I understood that 6 handles would also be compliant.

On another forum I got corrected and was told a disco ahead of the panel would work. Well I knew that but we often don't install a disconnect on a barn and then feed to a panel. Generally speaking, the main or handles are within the panel itself.

So when making statements , esp. on forums, we need to be more precise so others do understand that other possiblities could be compliant. I still fall prey to this from time to time.

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TOOL_5150

Yeah, that other forum is pretty dang strict. Theres a ton of knowledge there, but no humor what-so-ever. Say something off topic, and you get your head chewed off.

~Matt

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