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#97406 - 02/18/06 08:37 PM sub panel detached building  
watersparkfalls  Offline
Member
Joined: Mar 2005
Posts: 216
Washington...Not DC
i have a sub 50 amp sub panel that i want to put in a detached maint/gar building.
to save money on wire i am going to run two #6's for the lines and one #8 for the neutral(derating the neut)along with a #10 ground. my question is does this sound code compliant, we derate neutrals for the service feeders and this is going to be a feeder so it seems very complicit to me.

am i on the right page? any codes that i am missing which would forbid this derating?
thanks guys,
h20


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#97407 - 02/18/06 08:39 PM Re: sub panel detached building  
watersparkfalls  Offline
Member
Joined: Mar 2005
Posts: 216
Washington...Not DC
oh yea it is a metal building which i will bond the beam structure and will drive two ground rods down at the building too.


#97408 - 02/18/06 09:13 PM Re: sub panel detached building  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
By not knowing what your load is, I can't tell you that you can or can't derate the neutral. Also, I would be interested in how you terminate the neutral and ground wires in the sub panel. Where do you connect the Grounding Electrode Conductor in the sub panel?


George Little

#97409 - 02/18/06 10:02 PM Re: sub panel detached building  
ShockMe77  Offline
Member
Joined: Jun 2005
Posts: 821
Rahway, New Jersey
There's no need to install ground rods if you run a separate equipment grounding (bonding) conductor (E.G.C.) to the detached garage.

See more about this topic here: http://electrical-contractor.net/ubb/Forum1/HTML/006874.html


#97410 - 02/18/06 10:03 PM Re: sub panel detached building  
ShockMe77  Offline
Member
Joined: Jun 2005
Posts: 821
Rahway, New Jersey


#97411 - 02/18/06 10:12 PM Re: sub panel detached building  
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
Hold on. You must ALWAYS install a grounding electrode system for a detached building with more than a single multiwire branch circuit. It doesn't matter if your have three or four wires; with or without an equipment grounding conductor.
see 250.32


Earl

#97412 - 02/18/06 10:16 PM Re: sub panel detached building  
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
The neutral may only be derated if there is sufficient straight 240 volt loads to warrant it.
see 220.22


Earl

#97413 - 02/18/06 11:52 PM Re: sub panel detached building  
markp  Offline
Member
Joined: Apr 2004
Posts: 60
Kent, WA, USA
If your neutral busses are specifically listed at 75C and you use 75C rated wire, then #8 copper is fine for a 50A feeder because that wire is still rated at 50 amps.


Mark
Kent, WA

#97414 - 02/19/06 02:34 AM Re: sub panel detached building  
ShockMe77  Offline
Member
Joined: Jun 2005
Posts: 821
Rahway, New Jersey
My bad.

Yes, a grounding electrode MUST be installed on any detached building.


#97415 - 02/19/06 11:09 AM Re: sub panel detached building  
Speedy Petey  Offline
Member
Joined: Aug 2003
Posts: 173
Upstate, NY
Quote
Yes, a grounding electrode MUST be installed on any detached building.

...that is fed with a feeder.
If you only run a circuit no rod is needed.
See: 250.32


Speedy Petey

"Anyone who has never made a mistake has never tried anything new." -Albert Einstein

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