400 amp service with 2-200 sub panels

[james wuebker]

Ok, I'm putting in a 400 amp single phase 240volt service. I'm putting in a 320amp meter socket. I want to use the tap rules here.From the meter on the other side of the wall a 200 amp panel with a main breaker. Now I want a 200 amp disconnect,outside just below the meter for a house about 150' away. This will have a 200 amp in it with a main breaker. The book says to bond the neutral and the grounding wire at the first disconnect. With my 2 disconnects within 3' from the meter socket what would be the better way to properly ground the system. Thanks!

 

[don_resqcapt19]

Re: 400 amp service with 2-200 sub panels

James,
The service disconnects must be grouped. You can't have one inside and one outside for the same service.
Don

 

[ccha9219]

Re: 400 amp service with 2-200 sub panels

Put a 400 amp main breaker panel outside, run two sub panels from there. On in inside, the other to the house. go witha 200 main breaker at the house rather than an mlo

 

[james wuebker]

Re: 400 amp service with 2-200 sub panels

So Don, do I need a main disconnect for the 2- 200amp panel? This is what I'm try to get at. If I don't have to put a 400 amp disconnect after the meter this will save the customer a lot of money. So can I install the meter outside and run wires to my first 200 amp panel(sq.d 40 space). Then run another set of wires from the meter to another 200 amp disconnect which will be located next to the other 200 amp Sq. D panel and is for the house about 150' away. the house will have a 200 amp main in the panel(sq.d 40 space). If I can do it like this where would I install my grounding wire and the neutral together. The code says the first disconnect. Does the tap rules apply to this?

 

[don_resqcapt19]

Re: 400 amp service with 2-200 sub panels

James,
You would bond the neutral in both disconnects and install a grounding electrode conductor to both disconnects. The tap rules do not apply on the line side of the service disconnect. Conductors that are sized for the rating of the disconnect will be fine.
Don

 

[hurk27]

Re: 400 amp service with 2-200 sub panels

Jim why are you installing a disconnect at the 320 meter there is no requirment for it as the service conductors will be outside any buildings and you will have to install a disconnect or a main breaker panel at the house anyway and also install an GE also. 230.40 exception #3 allows for this then the panel at the house is treated just like a service panel.

 

[hurk27]

Re: 400 amp service with 2-200 sub panels

As for a better way of grounding. Having main bonding jumper father away from the service panel is not a better system useing 230.40 exception #3 will allow the main bonding jumper to be where it is needed at the house this will allow for a faster operation of breakers in the event of a ground fault since you wont have the long run to the meter disconect. What you are talking about when you are saying grounding is in realality a bond between the neutral and the equipment grounding conductors and the closer you place this bond to the place of the fault the faster the breakers will open. this is because of the resistance of the wire from the house to the meter. Grounding in the term of Earth is the grounding electrode and this has to be installed at the building being served anyway no matter where you put the disconnect. and to top it off you would have to install ether a disconect or main breaker panel at the house even if you install a disconect at the meter.

[ February 24, 2004, 07:21 PM: Message edited by: hurk27 ]

 

[hurk27]

Re: 400 amp service with 2-200 sub panels

Don where does it say the disconnects has to be grouped when two separate buildings are involved?
It only says where 6 means of disconnect are required then they have to be grouped. each building will allow 6 means of disconnect each. not 6 for both. Look at 230.71(A)

[ February 24, 2004, 07:19 PM: Message edited by: hurk27 ]

 

[james wuebker]

Re: 400 amp service with 2-200 sub panels

Good anwsers. Hurk27 The new service is going to be in the country. The person is going to building a large building for his old cars,shop and a show room first. He's also going to build a new house. He wants to build the shop for his cars first and then a month later start building his house. He wants the 200 amp panel(SQ.D 40 space) in his shop so he can work in it and also use the building to work out of when building his new house. So, he wanted a 200 amp disconnect setup so when he builds his house we can just come out of that to his new house. Yes I'll have to pull 4 wire and install another ground rod at the house but I think the setup should be OK. Anymore good ideas?

 

[don_resqcapt19]

Re: 400 amp service with 2-200 sub panels

Wayne,
In my opinion we only have a single service here and the service disconnets for a single service must be grouped. I guess if Exception #3 to 230.40 applies you would not need "grouped" disconnects. If you are building a "show room", I don't think that this exception applies.
Don

 

[russ]

Re: 400 amp service with 2-200 sub panels

Wayne:

I'd have to agree with you. The two mains being in or on separate buildings, would not be much different than if you had a meter on each building. There would be no question in that case and one no more unsafe than the other.

 

[hurk27]

Re: 400 amp service with 2-200 sub panels

230.40 exception #3 allows for set of service entrance conductors to feed each building. There is no requirment as to what the building would be used for. It just allows for it. now since it is allowed 230.71 allows for 6 disconects for each set of service entrance cables but each set of disconects have to be grouped not all together as this would disallow the exception#3 in 230.40 but each set of disconects as they are required to be on or at the closest entrance to the building has to be grouped. Now I do agree with that a disconect on the building with the meter would be a danger to firemen as responding to a fire in this building they could mistakenly think the disconect is for that building and turn it off without knowing that there is still power in that building this is why I brought up the exception that allows him to run the SEC directly to the house and place the disconect there. as he would be required to install a means of disconect there anyway.

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 a single service drop or lateral.


230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception Nos. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers,

230.72 Grouping of Disconnects.
(A) General. The two to six disconnects as permitted in 230.71 shall be grouped

 

[james wuebker]

Re: 400 amp service with 2-200 sub panels

Everyone one had great answers and this what I think I would like to do. I will either put a 400 amp main disconnect inside or outside, not sure where yet so in case of fire or any other enmergercies they can shut the power down in 1 click.2nd option is to group them together inside the first building and tag them very good. I believe both ways I'll be within the code unless someone can prove that I'm not correct doing it this way. It was great getting all of your feedback on this and I want to thank you for it. Thanks again everyone!
Jim

 

[hurk27]

Re: 400 amp service with 2-200 sub panels

Now I see what your were talking about Don. Since the cable running to the other bulding are infact feeders then the disconects on this building (where the meter is) has to be grouped. after reading what Rb said in the other thread it now makes sense.
I guess I learning too.

 

[pattbaa]

Re: 400 amp service with 2-200 sub panels

Jim; available is an out-door Service Equipment enclosure rated at 400 amps which is equipped with a meter-socket and two 200-amp 2-pole CB's for protecting two 200-amp feeders extended from the service location.

If you use a seperate meter-socket and two out-door 200 C-B's as Dis-connects you'll satifsy the "Grouping" requirement. This arrangment implies the Grounded Service Conductor terminating on "tap" connections in a W-P trough.

The Grounding Electrode Conductor must connect directly to the 400-amp Grounded Service Conductor. See "Exhibit 250.12" in the NEC 2002 "Handbook".

Please consider the "Access to Occupants" requirement of 230.72 (C) prior to locating both D-C's inside.

250.142 (B) prohibits using the Neutral for any required Grounding connections on the "Load" side of the D-C's.