Branch Panel Question

[Chris Skoczylas]

I did an inspection today on a home that was built in the 1960's and had a large addition added in 2006. A new 200 amp panel was installed and the original 125 amp panel is now a branch panel. My question is: The neutral and ground are common in the original panel. Should the original panel have been replaced so the neutral and ground wires are isolated.

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[Bill Kriegh]

Not necessarily. Most panels are constructed so that isolating the neutral buss from the panel box is easily accomplished. Doing this, and adding a listed ground buss so the grounds can be isolated from the neutrals is a pretty common way to handle the problem.

I suspect the major problem here would be getting a grounding conductor to the old panel, and without pictures other issues are tough to pick out - but I often find the water pipe bond and other bonding and grounding conductors that should have been moved to the service panel present in the old one.

Now, with all that, it's really going to depend on the size of the box whether the necessary rework, especially mounting the ground buss, is practical.

[Jerry Peck]

I suspect the major problem here would be getting a grounding conductor to the old panel,

That is the most frequent problem I would find with installations as Chris described - that the conductors to the original panel were service entrance where there was no separate grounding conductor, and the neutral conductor may well not have been insulated (was not required as part of the service entrance conductors) ... and the neutral is now required to be insulated and a grounding conductor installed - which typically would mean that the service entrance conductors would need to be removed and replaced with feeder conductors.

Sometimes the neutral would be insulated, but there would not be a ground, and installing a proper ground with the feeders conductors after the fact is usually more difficult that it would seem.

[James Duffin]

The biggest issue I run across when a service panel is converted to a sub-panel and the same three wire cable is used is the lack of a separate ground and neutral. The old panel is most likely OK.