multiple subpanels fed by one breaker / feeder

Jun 10, 2005 6 Replies

Greetings,



I would like to feed two main lug only subpanels from the same 100A breaker and the same 2 AGW Al SEU wire. I understand how the subpanel at the "end of chain" should be terminated but I am unsure of the "standard" way to attach the center subpanel.


Diagram =========================



200A Main 100A Sub 100A Sub

Thank you all very much in advance.



William



Additional Information =================================== I am sorry -- that was a typo -- I used SER. The panels are 25' and 50' away from the main panel.

Additional Questions Raised =================================== I looked at table 314.16(A/B) but was unable to locate the size box I would need for 10 2AWG wires. How many in^3 does each 2 AWG wire require? Is there another calculation mechanism I need to use?

William, Check out article 314.28 (2005 NEC) for additional information on sizing your junction box. Also check 338.24 for bending requirements of service entrance cable.

John Grabowski

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I don't know how it's *supposed* to be done, but I would look for a center panel with 2 sets of main lugs or an optional feedthru lug kit.

The other way I might try to do it is: Cut the wires at the first box and terminate normally, but strip an extra inch or 2 of insulation off the wires, and maybe leave a little extra slack. Then use big aluminum split bolt connectors (and black goop) to connect the outgoing cable to the exposed bare conductors of the incoming cable, then wrap with electrical tape as appropriate. (you won't need to wrap the grounding wire, obviously)

Best regards, Bob

The simplest way to do this is to replace the lugs that come with the panel with double barreled lugs. The new lugs will have two separate terminations with separate set screws.

Alternatively you can bring the two cables into the panel cabinet and terminate them on insulated triple or quadruple barreled lugs. You then run an appropriate sized jumper from the lug to the panels main lugs.

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