Sub-panel, grounds and neutrals questions


Old 07-20-16, 01:45 PM
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Sub-panel, grounds and neutrals questions

I have been living in my 100 year old house for 16 years, and finally got around to doing some rewiring. The wiring in the whole house was a nightmare, including some post and knob still being used, and cloth pre-romex cable, besides a medusa of Romex spiraling haphazardly in the basement. The previous owner put in a sub panel right next to the main panel. I recently noticed that they ran just standard aluminum entrance cable (two insulated conductors and one bare wire in a grey jacket) between the two panels (looks like no neutral, or using the bare wire as a neutral). The feed is off a double 100A breaker on the main, onto another 60A breaker on the sub. The sub has both 120 and 240 V circuits. Both the neutrals and grounds in the sub were both run to the same bar (which is not bonded to the box), which is connected to the bare ground wire from the main panel. The main panel has a wire to a ground rod outside. The main only has a neutral bar, which is bonded to the box, and also the subpanel only has a neutral bar, isolated from the box, but no ground bar either. I have never had any problems with this setup, but for safety's sake, should I change this setup to four insulated wires between the two boxes? I recently purchased two ground bars for the panels, because there are not enough spaces on the neutral bus to have a separate neutral on the bar for each circuit, and then all the grounds. Also, does it matter if the two panel enclosures are physically touching each other? Are the two breakers redundant, or is it OK to just leave them both? Also, is it acceptable to run branch wiring through the main box into the sub below it (space necessitates this).
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Old 07-20-16, 02:49 PM
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Neutrals and grounds are bonded together and to case only at the main service panel or at the first main disconnect.. There should be four wires to the subpanel. In the subpanel the neutrals are to be on an isolated bar all to themselves (not bonded to case), grounds are to be on their own bar that is bonded to the case.

If the subpanel is a main lug panel then the 60A is most likely not needed. You need to make sure the wire feeding the subpanel is rated for 100A if removing the 60A in the sub and rewiring directly to the bus in the sub. A picture will help if you can post one.
Old 07-20-16, 07:41 PM
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