Sub-panel Improvements

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Old 05-20-18, 12:12 PM
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Sub-panel Improvements

After purchasing a 30-year old house I want to make sure wiring is safe, if not up to NEC, and address concerns. One area of interest is the indoor sub-panel located about 30 feet from main 200-amp service panel in a connected bedroom/bath addition. The sub-panel has no main breaker and is feed by 50-amp circuit from the main service panel. Both the main panel and the sub are Square D QO. Whomever wired the sub-panel did not isolate the neutrals from the grounds; all run to the same bus that appears to be bonded to the box. Is there any reason why it should be left in this configuration? My plan is to install a ground bar in the sub-panel so I can isolate the grounds from the neutrals and make sure the neutral bus is not bonded to either the ground bus or the sub box. There is currently no earth ground directly for the sub-panel. Is there a reason or NEC directive to install a ground rod at the sub if it is approx. 30 feet from the main service panel? Because of location of a wooden deck, the closest I could drive a ground rod would be 12 feet from the wall where the sub is mounted. Is there NEC directive for distance from panel for the earth ground? Any suggestions for 1 rod or 2, and 1/2" or 5/8" rods? Thanks.
 
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Old 05-20-18, 12:59 PM
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Welcome to the forums.

Grounds... ground rods... water main bonding connect only at the main panel.
At one time code allowed three wires to a sub panel. The bar in the sub panel is a combination ground/neutral bar and probably has a bonding screw thru the bar connecting it to the panel.

Code for new work is now four wires between the main panel and the sub panel.
At the main panel..... the neutral and ground connect to the same bar.
The neutral bar in the sub panel needs to be isolated. (bonding screw removed)
The ground bar is attached directly to the metal panel.

In order to make any ground changes in the sub panel..... you'd need to run a new four wire cable.

Pictures of the insides of the panels are always helpful... How-to-insert-pictures
 
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Old 05-20-18, 02:17 PM
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The subpanel in the same building as its feeding panel does not need a ground rod.

If you did run a fat wire from the subpanel frame or ground bus to a ground rod then that would not count as satisfying any requirements.

If you drive an additional ground rod at a building and use it for something or other such as use it for an antenna, then to comply with code that rod must be interconnected with the other ground rods using a #6 copper wire run outdoors as much as possible. The new ground wire may be connected to an existing ground rod, the wire going to an existing ground rod, or the main panel whichever the new wire reaches first.
 
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Old 05-20-18, 06:35 PM
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Thanks for the reply. I attached three photos. One shows the four wires coming into the sub-panel. Another shows both connected to the bus bar. In the photo I can now see the bar is bonded with green machine screw to the box. The third photo shows the contents of the sub-panel. In the 200-amp main panel the ground from the sub-panel and the neutral are connected to the same bar.
 
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Old 05-20-18, 07:23 PM
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In a service panel the neutral and grounding conductors can connect to the same bar.

A three wire feeder to the same building as the service was never allowed as far as I know.
 
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Old 05-21-18, 07:13 PM
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The sub-panel is pictured. It does have a four-wire feeder from the main service panel. Is having the neutrals and the grounds connected to the same bar in the sub-panel a condition requiring action, such as adding a ground bar to the box and separating them from the neutrals?
 
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Old 05-21-18, 07:30 PM
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Yes.... that requires attention. The neutrals will remain there and an additional ground bar needs to be added. All the grounds get moved to it. Also... the green neutral bond screw needs to be removed after adding the ground bar.

You can have two grounds in one hole but neutrals must be one per hole.

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Old 05-22-18, 04:29 PM
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Thanks for the reply, Pete. The information is very helpful and appreciated. There are no drilled, raised and threaded holes for the ground bar in the box, so I plan to use self-tapping machine screws to attach it to the box. Next step will be to install the CAFI and dual function, CAFCI/GFCI, breakers I purchased.
 
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