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.
========================200A Main <---2 awg al---> 100A Sub <---2 awg al---> 100A Sub
Thank you all very much in advance.
Without knowing the proximity of the sub panels to one another, one method
would be to run the feeder into a screw cover box with individual cables out
to each panel. Keep in mind, unless these panels are for 240 volt only (no
neutral) you'll need to use SER (four wire) for single phase 120/240
==================================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?
Don't have a code book handy, but I believe you can't fill more than forty
percent. Personally, when it comes to boxes of any type, I like the biggest
I can fit rather than the smallest that's permissible
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.
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
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.
"This alternating current stuff is just a fad. It is much too dangerous
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