400amp Residential Service

[garwayne]

Hi,

I'm a newbie. Thanks much for this web site and forum, after poking around some it looks very well done and extremely useful.

Residential NEC is not my expertise, and I've seen several discussions relative to my question but not sure i saw any definitive answers. Here is my question:

Upon taking the advice of our local utility while constructing my house, I have mounted a SqD 400a Meter Combo box on a couple of 6x6 treated posts near the pad mount xfmr location with the intention of running the 2 - 200amp breaker circuits to either a 400a MLO or 2-200a MLO load centers located in my utlity room space. The inspector came and said nope, per 225 can't have these two feeding the same building, but If i want I can move the very same panel to the wall of the house and now everything is ok. I'm not buying it. I've poked around a bit and seems this not an uncommon arrangement. What's the story here? If the consensus is that this is ok, is there any ammo I can use with my inspector?

Thanks much in advance for any help anyone can offer up.

Gary

 

[augie47]

Sorry, I agree with the inspector. 225.30 limits you to one feeder (with some non-applicable exceptions)
By definition your 400 amp meter is a "structure" and the house becomes a second "structure".
Move it to the house and all is on one structure.

 

[iwire]

The inspector is correct.

II. More Than One Building or Other Structure

225.30 Number of Supplies. Where more than one building
or other structure is on the same property and under
single management, each additional building or other structure
that is served by a branch circuit or feeder on the load
side of the service disconnecting means shall be supplied
by only one feeder or branch circuit unless permitted in
225.30(A) through (E). For the purpose of this section, a
multiwire branch circuit shall be considered a single circuit.

There is nothing in 225.30(A) through (E) that would allow it.

 

[garwayne]

Thanks for the quick replies. It does seem a bit crazy to me though. I can see that if the structures (actual structures) had grounding/grounded conductor differences then there would be issues. However in this situation, electrically, there is no difference in any of the circuits if the panel is attached, moved 1 inch, or moved 40 feet. It just seems odd that the intent of the NEC would be to prevent this situation. (in my experience on the industrial side, discussion of intent comes up a lot)

Thanks again for your help,
Gary

 

[gary]

Hi,

Upon taking the advice of our local utility while constructing my house, I have mounted a SqD 400a Meter Combo box on a couple of 6x6 treated posts near the pad mount xfmr location with the intention of running the 2 - 200amp breaker circuits to either a 400a MLO or 2-200a MLO load centers located in my utlity room space. The inspector came and said nope, per 225 can't have these two feeding the same building, but If i want I can move the very same panel to the wall of the house and now everything is ok. I'm not buying it. I've poked around a bit and seems this not an uncommon arrangement. What's the story here? If the consensus is that this is ok, is there any ammo I can use with my inspector?

Thanks much in advance for any help anyone can offer up.

Gary

I did an identical installation a few years ago after checking first with the local AHJ. Requirements included using two main breaker subpanels at the house with the two panels in close physical proximity. The panels needed to be bonded together and connected to the same Ufer ground. Also, each conduit needed to have an EGC along with the feeders supplying each subpanel.

 

[kwired]

Instead of 2 separate 200 amp feeders make the same conductors one 400 amp parallel feeder and you will be code compliant.

There is no requirement that there be meter or disconnect near the transformer in the NEC. POCO can require this however.

At the house you can not use MLO panel(s) without having a main(s) someplace in or on the house.

 

[ceb58]

Instead of 2 separate 200 amp feeders make the same conductors one 400 amp parallel feeder and you will be code compliant.

First I would ask why are you taking the advice of the POCO on service size? What is the load calculation of the home?

I would think that 225.38 B may not allow this. Reason being every 400amp meter combo I have installed has 2-200amp breakers. I dont see having a parallel feed from 2 seperate breakers. The only way would be if the combo unit would accept a single 400amp breaker. But after thinking about it would the 2-6 disconnect 225.34A rule come in?

 

[kwired]

First I would ask why are you taking the advice of the POCO on service size? What is the load calculation of the home?

I would think that 225.38 B may not allow this. Reason being every 400amp meter combo I have installed has 2-200amp breakers. I dont see having a parallel feed from 2 seperate breakers. The only way would be if the combo unit would accept a single 400amp breaker. But after thinking about it would the 2-6 disconnect 225.34A rule come in?

If he uses same conductors as a parallel 400 he can not use the two 200 amp breakers in parallel.

225.30 does not permit multiple feeders to supply a separate building or structure with some exceptions. 225.33 allows up to six disconnects but they have to all be supplied by the same feeder in order to comply with 225.30.

 

[ceb58]

If he uses same conductors as a parallel 400 he can not use the two 200 amp breakers in parallel.

225.30 does not permit multiple feeders to supply a separate building or structure with some exceptions. 225.33 allows up to six disconnects but they have to all be supplied by the same feeder in order to comply with 225.30.

Yes, that was my point. If the OP's meter combo has the 2-200amp breakers then he could only use one to feed the home. Unless, as I said, the combo would accept a single 400amp breaker.

 

[Dennis Alwon]

I think what Kwired is saying is that once you got to the building you cannot terminate in two disconnects. I disagree since there is one feeder coming to the building and you could use the 10' tap rule to terminate in 2 different enclosures.

 

[mccayry]

Hi,

I'm a newbie. Thanks much for this web site and forum, after poking around some it looks very well done and extremely useful.

Residential NEC is not my expertise, and I've seen several discussions relative to my question but not sure i saw any definitive answers. Here is my question:

Upon taking the advice of our local utility while constructing my house, I have mounted a SqD 400a Meter Combo box on a couple of 6x6 treated posts near the pad mount xfmr location with the intention of running the 2 - 200amp breaker circuits to either a 400a MLO or 2-200a MLO load centers located in my utlity room space. The inspector came and said nope, per 225 can't have these two feeding the same building, but If i want I can move the very same panel to the wall of the house and now everything is ok. I'm not buying it. I've poked around a bit and seems this not an uncommon arrangement. What's the story here? If the consensus is that this is ok, is there any ammo I can use with my inspector?

Thanks much in advance for any help anyone can offer up.

Gary

Just curious as to why you wouldnt mount the meter base on the structure itself?

 

[kwired]

I think what Kwired is saying is that once you got to the building you cannot terminate in two disconnects. I disagree since there is one feeder coming to the building and you could use the 10' tap rule to terminate in 2 different enclosures.

What I am saying is you can only run one feeder to the building. It can be paralleled conductors. You can use tap rules and tap up to six disconnects off of the one feeder.

You can not run multiple feeders to the building. This is what the OP is wanting to do. He can make his two feeders into one parallel feeder and have two disconnects connected to it. The supply end will have to be a single overcurrent device, and the load end will need connected together to make proper parallel conductors out of it.

If the house were fed with a service instead of a feeder he can have up to six disconnects supplied separately from a common source. This will work if the meter/mains is moved to the house.

 

[ceb58]

What I am saying is you can only run one feeder to the building. It can be paralleled conductors. You can use tap rules and tap up to six disconnects off of the one feeder.

You can not run multiple feeders to the building. This is what the OP is wanting to do. He can make his two feeders into one parallel feeder and have two disconnects connected to it. The supply end will have to be a single overcurrent device, and the load end will need connected together to make proper parallel conductors out of it.

If the house were fed with a service instead of a feeder he can have up to six disconnects supplied separately from a common source. This will work if the meter/mains is moved to the house.

To try and get together on the same page. What I am saying is the same as what you are saying. The OP has a meter/combo away from the building. Every one I have dealt with has 2-200amp breakers for the feed. Now we are in agreement that he cannot run 2-200amp feeders. My point was unless the combo unit will accept a single 400amp breaker he could not run 2-200amp feeders to a single 400amp disconnect then tap to feed 2 panels.