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Thread: Split Bus Panels

  1. #1
    Join Date
    Feb 2007
    Location
    VA
    Posts
    246

    Split Bus Panels

    Can someone give a short tutorial on the residential split bus panel? What is the advantages or disadvantages?

  2. #2
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    21,838
    Quote Originally Posted by Greg1707
    Can someone give a short tutorial on the residential split bus panel? What is the advantages or disadvantages?
    First is the physical description: it's a main-lug panel, except instead of one long pair of stab buses, they're separated into two (or three) segments, each with lugs.

    The top bus segments are fed directly by the feeder. The lower (and middle) segments are each protected by a 2-pole ("main") breaker attached to the top segments.

    Any additional 2-pole breakers, usually the largest, are also attached in the top segment. As long as there are no more than six breaker handles, no single main is required.

    I'm not sure, but the primary advantage may be that you don't lose the entire service if a "main" breaker trips, or maybe that you omit the cost of a large single main breaker.

    I can tell you one thing: they make interesting alternatives to typical transfer-switch panels for stand-by generators when used with breaker interlocks, if you can find good panels.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  3. #3
    Join Date
    Sep 2004
    Location
    Durham, NC
    Posts
    5,252

    Lightbulb

    /larryfine ...
    I can tell you one thing: they make interesting alternatives to typical transfer-switch panels for stand-by generators when used with breaker interlocks, if you can find good panels.
    Would it be cost effect in new construction only or qualify/cost effective with an upgrade in service that might or might not include a genny ?
    I'm think other downline panels /services top side and house below, etc.
    If your even thirsty, your two quarts low.

  4. #4
    Join Date
    Sep 2004
    Posts
    1,468
    In general, they are no longer legal if the panel is a Lighting and Appliance panelboard. These must now be protected by one or two overcurrent devices instead of the old limit of six.
    Mark
    Kent, WA

  5. #5
    Join Date
    Jun 2005
    Location
    Delmarva, USA
    Posts
    1,645
    Back in the day, many contractors utilized the split-bus panels because they were much cheaper than the main breaker type.

    One of the inherint problems associated with this type was the sub-mains were usually limited to 60 Amps per section of the panel for lighting and receptacle loads. If loads such as a dryer or water heater (or A/C units) were installed in those sub-sections, nuisance tripping could occur of the 60 Amp breakers.

    Fortunately they have been "outlawed" by revisions in the 1984 Code

  6. #6
    Join Date
    Mar 2007
    Location
    MidWest
    Posts
    690

    Split Buss

    Funny this topic should come up, just this past weekend I had my service panel upgraded as it was a 30 year Old house with an old GE split bus panel the sub-main for the branch breakers was a 60a main and two additional breakers ahead of the main one for the electric stove (now gas) and one for the dryer, there was limited branches fed from the 60a main (I believe 16) therefore there was not a lot of room for additional circuits as we are completing some home improvements so there fore we upgraded to a square d QO 100A main with 32 spaces, plenty for me as the air conditioner was installed on interruptible service from the utility so I did not have to account for that load on my panel. Another thing from looking at the wiring diagram (I will double check when I get home) but on the branch breaker side I do not know if you can have a two pole breaker as the way the bus is connected some of the positions directly above and below are fed from the same bus, like I said I will look again and scan the wiring diagram.

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