400 amp Service Residential

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E16

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Iowa
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Electrical Contractor
Need some help on this. 400 amp service with tap box off side, the contractor wants to feed (2) 200 amp panels in new house, temp panel and future out buildings off of the tap box. I think we need to install fused disconnects and then feed the house or other buildings. He is planning on running un-protected to the main breaker in each panel. I have attached drawing of what is proposed.

Thanks
NEC 2011
 

Attachments

  • 400 amp service drawing.pdf
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@E16,

if I am following you correctly (and if I am not, my apologies) but it appears you are wanting to do an installation in accordance with 230.40 Ex. 3. Obviously if the building to which the temporary panel is located would have to meet 230.70(A)(1) and 230.71. Others may disagree but I see this as your only potential avenue.

if you happen to attempt to use 230.40 Ex. 3, then install two service conductors to the dwelling then it may bring up an issue with 230.2.

But hopefully others will chime in and assist more. The application (in fact a reverse application since you are wanting to go from a structure to the dwelling) is really irrelevant, the issue will be in compliance with 230.2 at this point. Now, if you can make the argument that they are "parallel" and electrically joined at both ends maybe...but the fact you are feeding two separate panels will create the problem.

When you see the use of two separate service entrance conductors from a meter enclosure back to back with two separate panel enclosures , it may look very similar to what you are trying to do...the only problem is in the back to back example only one set of was actually bought to the structure (in this example, not always) and so it is not a concern. In your example as drawn you will be brining two sets of underground service conductors to the dwelling which is against 230.2 (unless you can get permission from your AHJ for the application).

Just my thoughts on it....others will chime in.
 
I see that service needing two 200 amp disconnects adjacent to the meter with feeders to the sub panels. Grounding electrode system connected to each disconnect. No main breakers at the sub panels would be needed.
 
The meter socket, tap box and temp panel are mounted on boards that are then mounted to 4x4 post's. Feeders to the house will be underground.

thanks
 
They are not feeders to the house unless you have overcurrent protective device at the source. They are service conductors. What I would do is make that a parallel run to a trough or JB at the house and then put 2 - 200 panels off the trough. I believe this would be compliant
 
gaelectric said:
I see that service needing two 200 amp disconnects adjacent to the meter with feeders to the sub panels. Grounding electrode system connected to each disconnect. No main breakers at the sub panels would be needed.
Click to expand...

That is what I was thinking also what code section would you reference? 230.70 (A) (1)??
They are trying to use 240.92 (D) but I think this is for Supervised Industrial Installations only.

Thanks for all the help.
 
gaelectric said:
I see that service needing two 200 amp disconnects adjacent to the meter with feeders to the sub panels. Grounding electrode system connected to each disconnect. No main breakers at the sub panels would be needed.
Click to expand...


That would be a violation of 225.30. One feeder to the building- not 2
 
Dennis Alwon said:
That would be a violation of 225.30. One feeder to the building- not 2
Click to expand...

So looks like parallel run of Service conductors to house and two 200 amp panels with main breakers.

Thank you everyone for the help. :thumbsup:
 
Dennis Alwon said:
They are not feeders to the house unless you have overcurrent protective device at the source. They are service conductors. What I would do is make that a parallel run to a trough or JB at the house and then put 2 - 200 panels off the trough. I believe this would be compliant
Click to expand...

One way to skin the cat.....;)..given the situation presented it may be the only way if the OP still wishes to go that route.
 
MasterTheNEC said:
@E16,

if I am following you correctly (and if I am not, my apologies) but it appears you are wanting to do an installation in accordance with 230.40 Ex. 3. Obviously if the building to which the temporary panel is located would have to meet 230.70(A)(1) and 230.71. Others may disagree but I see this as your only potential avenue.

if you happen to attempt to use 230.40 Ex. 3, then install two service conductors to the dwelling then it may bring up an issue with 230.2.

But hopefully others will chime in and assist more. The application (in fact a reverse application since you are wanting to go from a structure to the dwelling) is really irrelevant, the issue will be in compliance with 230.2 at this point. Now, if you can make the argument that they are "parallel" and electrically joined at both ends maybe...but the fact you are feeding two separate panels will create the problem.

When you see the use of two separate service entrance conductors from a meter enclosure back to back with two separate panel enclosures , it may look very similar to what you are trying to do...the only problem is in the back to back example only one set of was actually bought to the structure (in this example, not always) and so it is not a concern. In your example as drawn you will be brining two sets of underground service conductors to the dwelling which is against 230.2 (unless you can get permission from your AHJ for the application).

Just my thoughts on it....others will chime in.
Click to expand...

230.40 exception 3 is wide open for interpretation in some cases. Take OP's example - is his temporary or the future outbuildings accessory buildings to the dwelling? On a typical city residential lot maybe they are, out here in farm land they aren't necessarily accessory buildings to the dwelling, and have service conductors run to each and every building sometimes, all from the same point.
 
I thought in order to be parallel the conductors have to terminate on the same buss or MB. If you parallel this and branch off to two MB panels isn't this the same as 2 200 amp services since they terminate in different panels. ,If this is a residential service couldn't you just pull 600 aluminum through 3" set a trough and branch to each panel this may save time and money. Just asking, thanx
 
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FREEBALL said:
I thought in order to be parallel the conductors have to terminate on the same buss or MB. If you parallel this and branch off to two MB panels isn't this the same as 2 200 amp services since they terminate in different panels. ,If this is a residential service couldn't you just pull 600 aluminum through 3" set a trough and branch to each panel this may save time and money. Just asking, thanx
Click to expand...

230.2 Number of Services.
A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D). For the purpose of 230.40, Exception No. 2 only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service.
Click to expand...

Up to six sets like this (plus exceptions for fire pumps, emergency, stanby...) is still considered only one service. One service can have up to six disconnecting means plus exceptions for fire pumps, emergency systems .... and a few other special items.

To be parallel the conductors must be joined together at both ends. Does not even need to be a panel bus or MB that they are joined by.

The complication with the OP is whether or not we can have additional service disconnecting means at separate structures supplied from the same service drop, lateral, or other point in the service, the run to the house is just fine if it were the only thing supplied.
 
I assumed one service meant one meter.. I dont have enough experience or understanding on the subject although it seems to mean one drop from poco. There seems to be multiple ways for this to work unless as stated the inspector wants disconnect to be where service began and not multiple locations. One main disconnect could solve that? Can a disconnect be put before the meter?.
 
electricalist said:
I assumed one service meant one meter.. I dont have enough experience or understanding on the subject although it seems to mean one drop from poco. There seems to be multiple ways for this to work unless as stated the inspector wants disconnect to be where service began and not multiple locations. One main disconnect could solve that? Can a disconnect be put before the meter?.
Click to expand...

Look at definitions that include the word "service", there are several. None of them use the term meter to qualify something as being a service component. You can have a service with no meter at all - does happen with fixed loads that are billed a rate based on the supplied load. Some examples include street lighting and signs.

It has been said here before a meter is just a wide point in the service conductors. It's presence doesn't change any rules, the presence of a service disconnecting means makes a change in what you have there. Meters can be on the load side of the service disconnecting means, even POCO meters, which is exactly what you have with large multi-tenant buildings with multimeter packs. If more then six meters with disconnects you would have violation of the six disconnect rule so there generally is a service disconnect ahead of the meters. Just so happens to be designed in a way that it would be difficult to tap onto unmetered power so that most POCO will accept it.
 
Ill read up on that. We did a job in oklahoma and we were required to put a non fused disconnect before the meter. (Poco drop , riser, disconnect, meter , 400 a disconnect to customer panel) . Very interesting how that can change a install . Another job bldg 1 fed bldg 2 . Bldg 1 fed bldg 3 also . Bldg 2 fed another bldg.( 2/a) Customer expanded bldg 2/a and needed another panel. We added it , fed from bldg 1. Inspector flipped out. Bldg cannot be fed from 2 services. After metting with cheif inspector it was determined it was not 2 services to bldg. I thought I was told 1 add gets 1 service . So its not likely you could have to services to 1 bldg.
 
electricalist said:
Ill read up on that. We did a job in oklahoma and we were required to put a non fused disconnect before the meter. (Poco drop , riser, disconnect, meter , 400 a disconnect to customer panel) . Very interesting how that can change a install . Another job bldg 1 fed bldg 2 . Bldg 1 fed bldg 3 also . Bldg 2 fed another bldg.( 2/a) Customer expanded bldg 2/a and needed another panel. We added it , fed from bldg 1. Inspector flipped out. Bldg cannot be fed from 2 services. After metting with cheif inspector it was determined it was not 2 services to bldg. I thought I was told 1 add gets 1 service . So its not likely you could have to services to 1 bldg.
Click to expand...
In that case it was not two "services" it was 2 feeders supplying the building. 225.30 does prohibit a building from be supplied by more then one branch circuit or feeder, with some special conditions like fire pumps, emergency systems, etc. You still can have up to six disconnecting means at the end of the feeder though, again with some special conditions like fire pumps, emergency systems, etc.
 
electricalist said:
So the 2 panels in bldg 2 a are branch circuits ? Mwbc? Sorry for my terrible understanding of my terms. Ty
Click to expand...
They are most likely feeders, unless there are no additional overcurrent devices before the load(s).

See definitions of branch circuit as well as feeder.
 
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