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Thread: 320 Amp Service, Tow 200A Panels?

  1. #1
    Join Date
    Apr 2005

    320 Amp Service, Tow 200A Panels?

    Hi all. This is my first posting and any help will be immensely appreciated.

    The utility company will be installing a 320A rated meter on a new building for service. From the meter, can I install two adjacent 200A panels inside the building for the service? Are they fed separately from the meter? Is one panel my only option? What are my options? The building is a residential two story (up 1,100 sf apartment/down a 2,000 sf shop (the shop belongs to the property owner will lease the apartment to a future tenant.) Also, do I need disconnects for the panel and or panels? The service will be 120/240 single phase. I've been an electrician since 1988 and this year I became a contractor. As far as the setup and configuration goes, this one has me stuck. Thanks

  2. #2
    Join Date
    Sep 2004

    Re: 320 Amp Service, Tow 200A Panels?

    Most 320A meter bases have lugs that are listed to accept multiple wires in the same hole (one of the few lugs that are). My meter base (Milbank) required that each wire be the same size and there is a narrow range of wire sizes you are allowed to use when double lugging. So what you'd generally do is run two sets of 3/0 copper from each lug running one wire from each lug to a 200A panel. Same with the neutral, but you could drop back a size or two (but don't go under 1/0, or whatever size is required by 250.66, so you have more options as to where to connect the ground electrode conductor).

    You need a service disconnect. Typically, you just use the 200A main on two panels for this. The panels must be grouped in order to do this. If you'd rather have a 200A panel downstairs and a 200A panel upstairs, then perhaps you'll want two 200A disconnects outside each going to a 200A MLO panel. If this is going to be a partial rental, I think this would be a better approach as each tenant needs access to their disconnect. If both tenants can access the inside area behind the meter, then maybe the dual 200A panel approach would be acceptable.
    Kent, WA

  3. #3
    Join Date
    Feb 2003

    Re: 320 Amp Service, Tow 200A Panels?

    You can serve two, 200-ampere panels if the load does not exceed 400-ampere or 320-amperes continuous.

    The NEC permits the service panels to be located inside, however, I would check with the local AHJ before you make that decision.

    You basically have two options. You can install a single disconnecting means for both 200-ampere panels or incorporate a main breaker/switch at each panel as your service disconnecting means. The first option would allow you to install the "unit" panels just about anywhere you want, where as the second would require you to group the two panels together.
    Bryan P. Holland, MCP
    NEMA - Codes & Standards

  4. #4
    Join Date
    May 2004
    Central Kentucky

    Re: 320 Amp Service, Tow 200A Panels?

    A 320 amp self contained meter base will have threaded posts, that You will bolt double lugs onto for Your 2 conductors.
    If You go straight through the outside wall, You can go into 2 200 amp panels directly.
    The only issue will be the rented space below, the Apartment Tenant will have to have access to the panels, & that might not work in this situation.
    If that is the case, You would need to use disconnects, & feed from there to Load Centers on each floor.
    Just My opinion, but I believe I would install a 2 meter combo with 2 200 amp breakers, then feed to 2 different load centers on each floor.
    This would allow each area to be metered issue that will surely have to be addressed later on.
    The Owner probably doesn't want to guess at the KWH usage for the Person renting the shop space.

  5. #5
    Join Date
    Aug 2004
    Las Vegas

    Re: 320 Amp Service, Tow 200A Panels?

    The 400 amp milbank meter pedistals I get come with double lugs for this. They also make a 400 amp meter pedistal with 2) 200 amp breakers for this.

    I think Megawatt has the best answer. 2 meter combo set up with a outside disconect.


  6. #6
    Join Date
    Feb 2003
    Portage, Indiana NEC: 2008

    Re: 320 Amp Service, Tow 200A Panels?

    Sounds like the utility supply's the service equipment in your case (up to the meter) this only leaves you with two option's: Install two disconnects one on each side of the meter if space permits, the disconnect feeding the apartment can have 2/0 all the way to the no-main panel in the apartment 310.15(B)(6). But if the shop is a commercial space it would require 3/0 to just the shop's panel, The second option is to locate both panels in the same location with main breakers but both panels will have to be accessible to both the owner and the renter. I would pick the first choice. In ether case the dwelling only needs 2/0 copper ran to it.
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

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