sub panel main breaker

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Michael White

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Apache Junction Arizona
I installed a sub panel in a detached garage fed from a 50a breaker in main house panel. It was approved as a main lug only by Peoria Az. plan review. When it was inspected the inspector said that since it contained more than 6 breakers it was required to have a main breaker. I stated that the rule only applied to services, not sub panels. He said that since you couldn't see it from the main panel it needed the main. To avoid further argument I replaced the panel with a 100a with main breaker. Now he says that the main must be 50a max, so that it wouldn't overload the 50a feeders. I stated that the main was only being used as a switch and since the feeders were already protected at 50a it was impossible to overload the feeders with a downstream 100a. He is adamant that I have to change the main, does he have any grounds for this ruling.
 
The first one, yes, the second one, no. The feeder is protected at the source, unlike a typical service feeder.
 
I’ve seen several threads on this subject and the one thing I’ve not seen discussed is the definition of ‘detached’. For example, if the structures share a wall, but you have to go outside to get from one to the other, is it ‘detached’?

Is ‘detached’ defined in the NEC?
 
I would say that detached is defined as not attached. Having to go outside to another door is no different than going to another room inside, in my opinion.
 
Michael White said:
I installed a sub panel in a detached garage fed from a 50a breaker in main house panel. It was approved as a main lug only by Peoria Az. plan review. When it was inspected the inspector said that since it contained more than 6 breakers it was required to have a main breaker. I stated that the rule only applied to services, not sub panels. He said that since you couldn't see it from the main panel it needed the main. To avoid further argument I replaced the panel with a 100a with main breaker. Now he says that the main must be 50a max, so that it wouldn't overload the 50a feeders. I stated that the main was only being used as a switch and since the feeders were already protected at 50a it was impossible to overload the feeders with a downstream 100a. He is adamant that I have to change the main, does he have any grounds for this ruling.
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The inspector is incorrect regarding the 100 amp CB. The 50 amp feeder is protected at the supply end by the 50 amp OCPD, the 100 amp CB is the required disconnecting means. That is code compliant.
 
LarryFine said:
I would say that detached is defined as not attached. Having to go outside to another door is no different than going to another room inside, in my opinion.
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I tend to agree. The reason I brought this up is the following case (my residence):

I have a pool house with a 100A MLO panel with 16 spaces, 10 used. The pool house is 20 feet from my house where the feeder originates. A brick wall on my house extends away from the house and 20 feet later, it becomes a wall of the pool house.

By this definition, they are indeed attached. And that what the pool installer who put in the panel told me when I asked him about it. He is a licensed EC.

I just look at it subjectively and wonder if it meets the intent of the rule!!??
 
In this instance, I would have to say that the brick wall does not qualify the two structures as attached. A properly-secured back-fed breaker would suffice.
 
Arguably if you have a feeder between 2 structures you have attached them :) ( tongue firmly in cheek)

At some point the cost of a common mass produced panel with a main breaker is cheaper than the cost of figuring out if you have a detached structure or not. IMHO the brick wall that retirede describes ties the two buildings into a single structure, but this misses the intent of the code.

Along the same vein but going in the opposite direction: If you have a pole mounted panel a couple of feet away from the building served, IMHO they are technically separate structures but per a common sense understanding of the code should be considered one structure.

Back to the OP, you are only permitted a single feeder (with some exceptions) to a detached structure, and must have a disconnect at the detached structure. I agree with what others have said: the inspector was correct in requiring a main disconnect, but incorrect in requiring a 50A breaker when a 100A breaker would serve as that disconnect.

-Jon
 
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