sub-panels

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pomps

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I have a 400 amp sub-panel 480v and have to put in a low voltage 208/120 panel along side of it. My question is on a normal install you bond the ground and neutral together on a seperatly derived system do you do the same when your 480v panel is a sub panel?
 
Internal to the 480 volt panel, you keep the grounds and neutrals separate. After you transform down to 120/208V, you bond the ground and neutral at the first opportunity. That will normally be internal to the first panel, which is to say, your 120/208 panel. You don't get a "separately derived system" at the primary of the transformer, but rather at the secondary.
 
On the 120/208 side, you'd bond neutral and ground somewhere between the stepdown transformer and the 120/208 panel. It doesn't matter whether the 480 is a subpanel or not.

Jim T
 
is it acceptable to bond the neutral and ground at the xfmr secondary winding to a ground rod that is used by another service panel?:
 
steveng said:
is it acceptable to bond the neutral and ground at the xfmr secondary winding to a ground rod that is used by another service panel?:
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Steve, see 250.30(A)(7).

Also, all electrodes are required to be bonded together by 250.50 and 250.58.
 
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