200A Combo Meter for Service with Sub-Panel in Garage

[jar546]

So here we go. Hopefully we will all learn something or at least refresh our memories with this situation.

Let's start with this. Below is the photo of a combo 120/240v, 200A meter and disconnect that will be mounted on a single-family residence. Let's say this gets fed from above with 4/0 aluminum SE cable. The POCO will tie into the SE cable above. The main then feeds to the garage where the main panel (sub-feed) is supplying all of the circuits to this single-family residence.

Questions:

1) What are the minimum size copper conductors that are allowed to feed the main panel (sub-feed) in the garage IF all of the circuits for the entire house originate from that panel?

2) What are the minimum size copper conductors that are allowed to feed the main panel (sub-feed) in the garage IF most of the circuits are in the sub-fed main panel but there is a branch circuit outside for the AC that originates in the exterior combo-meter panel?

What say thee?

 

[ICE]

Not enough information. What is the rating of the breaker that feeds the sub-panel? For example, let's say that the breaker is 100 amp because that's the minimum allowed for a single family dwelling. In that case assuming that the sub-panel is rated for at least 100 amps the conductor shall be #3 cu if it has 75° insulation or #1 al again at 75°.

I know where you are going with this. The times .83 can't be used in either scenario because the panel with the main disconnect has breaker slots that could be used for other loads.

You need a main lug only panel to use the .83 multplier.

 

[jar546]

200 amp main that parallels to the sub so only 1 main in the combo. Yes, you know where I am going with this. You are spot on.

The question is your interpretation. If no other breakers are installed in the combo other than the main which feeds the main-sub would it still be a violation? Is it OK until someone puts in a circuit outside in the combo panel?

 

[ICE]

200 amp main that parallels to the sub so only 1 main in the combo. Yes, you know where I am going with this. You are spot on.

The question is your interpretation. If no other breakers are installed in the combo other than the main which feeds the main-sub would it still be a violation? Is it OK until someone puts in a circuit outside in the combo panel?

Our policy is to not allow the .83 if there are any additional breaker slots....empty or not.

 

[jar546]

Our policy is to not allow the .83 if there are any additional breaker slots....empty or not.

Interesting and I agree. Is that written or unwritten policy? Can you cite that if you had to?

 

[ICE]

Well I haven’t seen it in writing and I haven’t had to cite it....Not many people that I deal with have that much code knowledge. One in a hundred have a code book.