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Old 02-10-2011, 01:54 PM   #1
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Old Fuse Box


Many years ago I had a new service panel put in and a circuit run from it to the old service panel. The old panel has a non-isolated neutral. The new circuit is three conductor plus ground but the ground is just hanging loose in the box. There is no other grounding on this box. That was removed when the new service was installed.

From what I have read it would be better if the box had an isolated ground but short of replacing the box that is not going to happen. (Or maybe there is a way of isolating the neutral bus.) First I think the ground wire should be terminated in the box but I don't know how. It is aluminum strand for the 100 A circuit.

Secondly as I replace old circuits in this old fuse box how should I terminate the ground wires. Should I just add them on to the neutral bus?

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Old 02-10-2011, 07:06 PM   #2
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Old Fuse Box


As you replace your circuits, run them to the new panel on new breakers instead the old panel. Once you have all the circuits rerun and fed from the new panel, you can remove the old panel and wiring. I wouldn't feed the new circuits from the old panel again unless it was temporary. You can use junction boxes to extend any old cables to the new panel that you plan on retaining.

Probably the only way to isolate the neutrals and grounds is to install an insulated neutral bus bar, and move all the whites to that. Most old panels have the nuetral bar permanently bonded to the box itself. Probably not worth doing to an old panel, better to get rid of it entirely.

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Old 02-11-2011, 09:35 PM   #3
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Old Fuse Box


@Collector: Thanks for your post. I have using circuits in the new box. There's only one slot unused. I guess I really should replace the old box. Probably a job for a professional. In the mean time I'm just going to terminate the neutral and ground on the neutral bus.
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Old 02-11-2011, 10:27 PM   #4
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Old Fuse Box


I don't know about aluminum as a ground , I don't like that ides ....... If your gonna use the old panel and have a cold water pipe near by I run a solid copper to it for a ground or drop another ground rod. What size wire did they feed the old panel with anyway ?

The only time ya really need an isolated ground is computer equipment anyway , even being isolated the neutral n isolated ground end up in the same spot .
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Old 02-12-2011, 06:05 AM   #5
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Old Fuse Box


The new panel has (or should have) a #6 copper wire (up to 100 amp service) from the ground bus over to the main cold water pipe within 5 feet of where the pipe enters and without the meter in between. A pair of 8 foot ground rods 7 feet apart can substitute for the water pipe connection, if the soil conductivity is really good then one rod will suffice.

The old fuse box should have a ground wire between it and the new panel. This ground wire would be at least as thick as the heaviest circuit cable still there. (Probably #12 gauge)

If you run out of spaces in your main panel you could install a new subpanel which will finally take up all the circuits remaining in the old fuse box. A #6 cable and 60 amp breaker pair in the main panel is probably the best choice to feed the subpanel.
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Last edited by AllanJ; 02-12-2011 at 06:11 AM.
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Old 02-13-2011, 08:37 PM   #6
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Old Fuse Box


There is no inscription on the sheath of cable running between the new and old boxes. The circuit breaker in the new box says 125. The new box is grounded to the water service before and after the meter with 1/4" stranded aluminum. There are also two ground stakes.

Thanks to all who replied. I am convinced I ultimately need to replace the old box. The existing system is a safe as can be until that box can be replaced.

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