400 amp service with 2-200 amp subs

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james wuebker

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Iowa
Putting in a 400 amp service single phase 240v. Got a 320a meter socket will install on building. On the inside wall, 2' away from the meter will be a 200 amp panel with a main in it. OK just below the meter on the outside of the building I'm going to install a 200 amp disconnect for the house about 150' away which will have a 200 amp panel in it with a main breaker. Does the tap rules apply and is this OK do it this way. Also where would be the first disconnect if bonding the neutral and the grounding wire of the system?Ideas or should I start with a new game plan.
Thanks!
Jim
 
Re: 400 amp service with 2-200 amp subs

Jim need a little more info.Is there more than one building.Is there one meter or two meters.Is this all one adress.
 
Re: 400 amp service with 2-200 amp subs

Milbank makes a 320A meter pedestal with lugs suitable for 2 wires per lug. In WI your installation is not unheard of. Bonding is not needed if using cable (SEU), or PVC. Grounding, however is done based on 400Amps equivalency. We use #4 cu from panel(s)/disconnect(s) to a 1/0 cu GEC. Ground rods are easy...#4 cu
Your instalation is similar to the picture in NEC Handbook (NFPA) under 250.66 (Exhibit 250.64)
 
Re: 400 amp service with 2-200 amp subs

tehea is on the right track. I would be using a Milbank meter base. This is how they would like it done. It's out in the country and the farmer want to build his showcase building that he shows his old cars and he can also work on them .He wants a 200 amp Sq.D 40 space panel in that build then after that is finished he's building his new home about 150' away from there and also wants a 200 amp panel in that.So I was going to run a set of wires from the meter to the first 200 amp panel Sq.D(40 space) that will be in his first building for his cars. Then I wanted to setup another disconnect near the meter for when he's ready to build this house. So, The first panel will be in his car building and will I have to install the 200 amp disconnect for his house in that build. Does disconnects have to be grouped together. I'm hoping the tap rule applies. Using only 1 meter for all.
Thanks!
Jim
 
Re: 400 amp service with 2-200 amp subs

In my area, they wouldn't allow it as you described. Correct me if I'm wrong but you plan to use a 320A meterbase and have one 200A panel inside the building the meterbase is mounted on and another 200A disconnect on the outside of the same building to feed service to another structure in the future? So you will have (2) 200A mains fed from the same meterbase/service? That's okay but aren't you required to have the disconnects for the service grouped together? In my area they won't consider them "grouped" if one is inside and one is outside. They make us put them both outside, (2) 200A 3R disconnects next to the meterbase, or a 200A MB loadcenter and an indoor 200A disconnect both inside. 230.72(A) Grouping of Disconnects.
 
Re: 400 amp service with 2-200 amp subs

In my opinion yuor proposed installation violates the code.

230.40 Exception No. 3 permits the service entrance conductors supplying a single-family dwelling unit and a separate structure to be supplied from the same service drop or lateral. In the installation you describe you are running a feeder to a house, not service entrance conductors. Therefore 230.40 Exception No. 2 will apply and the service disconnects will have to be grouped.

If you didn't place the main for the dwelling unit at the accessory building, but instead routed service conductors from the meter socket to the dwelling unit, then 230.40 Exception No. 3 would apply.

There would be no limit to the length that you would be permitted to run these conductors providing that these conductors are installed as service conductors in accordance with Article 230.
 
Re: 400 amp service with 2-200 amp subs

amptech, I can put both panel and disconnect inside his building. Read 230.71(A) Let me know want you think.
 
Re: 400 amp service with 2-200 amp subs

James,

As long as both your service disconnecting means are grouped inside the accessory building there is no problem. You now have two service disconnecting means grouped at a common location. This complies with 230.72 and 230.40 Exception No. 2.

230.71(a) addresses the maximum number of service disconnects. Six or less is permitted at one location.
 
Re: 400 amp service with 2-200 amp subs

Ok so we have a 320 meter base and one back to back 200 then a disc. adjacent to the meter,they are grouped together.Either at the first point of entry or adjacent to,as long as the tap rule isn`t
violated what article would prevent this installation.I have done several 600 amp single phase residential services that have done just this.A 200 amp disc. adjacent to the meter and 2 200 M BKR panels back to back,Never been tagged for it and I would argue if I was !!!!!The 200 disc. is usually for a garage or shop Once for landscape lighting and irrigation ,so where is the violation as long as the seperate panels are witrhin the tap rule distance and the back to back meet requirements what`s the article ?? Ok I am a New Yorker ,but I am from mississouri show me
 
Re: 400 amp service with 2-200 amp subs

I must have misunderstood your post. You have a 200 amp loadcenter backed up to the meter socket. This panel is located inside the building. Now you put a NEMA 3R 200 amp disconnect located outside beside the meter socket to serve another building. You consider these grouped?
 
Re: 400 amp service with 2-200 amp subs

230.40 Exception No. 3: A single-family dwelling unit and a separate structure shall be permitted to have one set of service entrance conductors run to each from one service drop or lateral.

This exception permits service entrance conductors to be run to the other building not feeder conductors. If feeder conductors are installed, the service disconnecting means supplying the feeder conductors must be grouped with the other service disconnecting means supplied by that service as required by 230.40 Exception No. 2. Otherwise the service drop or lateral is only permitted to serve one set of service entrance conductors per 230.40.

The danger of the installation you described is that emergency personnel could confuse the 200 amp NEMA 3R disconnect as the disconnecting means for the 200 amp panel located in the dwelling unit.
 
Re: 400 amp service with 2-200 amp subs

Rb, I was thinking the same wat as you about in case of an emergery. I beleive I can put the 200 amp panel and the 200 amp disconnect for his house inside the first building where his meter is and be within the code. But putting a 400 amp disconnect for everything would be and safer thing just in case there was and emergery and confusion set in.
Thank you everyone for your time.
Jim W.
 
Re: 400 amp service with 2-200 amp subs

Charlie, I believe that would be compliant as the conductors would be service conductors if they came straight off the lugs in the meterbase with one set going into the first structure and the second set directly to another. But if both disconnects are located at the first structure they have to be grouped and I would not consider one inside and one outside as grouped. I usually use a Siemens 400A meter main with (2) 200A breakers built in. It isn't much larger than a 320A meterbase and makes for a neat installation.
 
Re: 400 amp service with 2-200 amp subs

That has become my favorite saying recently,with our growth surge,county AHJ`S are scrambling and sometimes invent their interpitations.So I have been a show me person,Where in the NEC does it say that I will ask, politley of course.Usually it all works out fine but sometimes I have to go to the chief and see what he says.And no not from missiourian :D
 
Re: 400 amp service with 2-200 amp subs

Amptech,

You nailed it, that is exactly my point. If you locate the mains at the first building they must be grouped. Or use 230.40 Exception No. 3 and run service entrance conductors to the second building.

[ February 25, 2004, 07:23 PM: Message edited by: rb ]
 
Re: 400 amp service with 2-200 amp subs

I am a little confused as to why you would use a 320 amp meter base for a 400 amp service instead of using a 400 amp service made up of a ct can and 400 amp bussing. ?
 
Re: 400 amp service with 2-200 amp subs

The 320 socket is rated 400 amp max 320 continuous.

If this service draws more than 320 continuous the calculations are wrong and you also will have exceeded the ratings of one or both 200 amp panels.

A 320 socket for 400 amp services is what the POCOs here expect, CT metering starts at 600 amps around here.
 
Re: 400 amp service with 2-200 amp subs

It sounds like this is more like a distribution point then an urban dwelling service.

?tehea is on the right track. I would be using a Milbank meter base. This is how they would like it done. It's out in the country and the farmer want to build his showcase building that he shows his old cars and he can also work on them?

547.9 Electrical Supply to Building or Structures from a Distribution Point.
 
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