My 1966 house has ehat I believe must be the original service panel. It is a 100 amp GE with two pullouts (one controls the branch circuits and a subfeed (which runs to the central AC fused disconnect); the other controls the range). There are 8 fused branch circuits (2 20A, 6 15A). Although the wiring is K&T, they actually ran EGCs. The problem is that there is only a neutral bus in the panel. As a result, most of the spaces on the bus have more than one wire underneath. I'd like to add a grounding bus, move all the EGCs to it (one wire per screw), leave the neutrals on the existing bus (one wire per screw), and bond the two buses. Can this be done? If so, how?

 

If there's ample space in the panel. You could pigtail (splice) the equipment grounding conductors. DON'T pigtail the neutrals.

 

If there is no main disconnecting means upstream from your panel, that is, between the panel and the meter, you are not required to have separate grounds and neutrals. You can have two buses if you like, but they must be electrically connected together so that all grounds and neutrals at the same electrical point. I added a second bus bar to my panel. You can buy them at major home centers, for $5 to $8. To install you must sand all the paint off the area of the panel enclosure where you will install the new bus bar. You must use self-tapping screws, you will need to drill pilot holes of proper size for the screws you use. You may not use sheet metal screws. I connected my two bus bars together with a length of #6 bare copper, using one of the terminals on each bus. That ensures that they are the same electrical point. But I wouldn't go to the trouble of putting only grounds on one and neutrals on the other. That makes zero difference to electricity, it would merely be aesthetic.

Hope that helps.

Juice

 

That does help, thanks. Since the neutrals and EGCs don't have to be on separate buses, would it be possible to buy a, say, 24-space grounding bus and use it to replace the existing bus? The only downside I can think of that would render this idea unusable is that the ground bus may not have a space large enough to handle the incoming neutral from the meter.

 

The grounded current carrying conductors that most of us call the neutral must be terminated with only one conductor per terminal. The label in the panel will tell you if any of the terminals are suitable for more than one conductor. If they are you can put that number of equipment grounding conductors under one terminal but you still must keep the neutrals to one per terminal. This is because as the loads on the neutrals vary they will expand and contract at different rates and that would cause the termination to loosen, arc, heat , and fail.

This is going to seem like nitpicking but I'm going to tell you anyway. The additional buss bar that you install in that panel's cabinet should be the one that is available from the original equipment manufacturer. That is the only buss bar that is listed for use in that cabinet by an electrical testing laboratory. When I was in the military and we had to add Equipment Grounding Conductor buss bars to older panel cabinets we bonded the buss bar to the enclosure by connecting it to a terminal lug that was fastened to the cabinet in accordance with the lug manufacturers instructions. This was to avoid depending on the untested mounting hardware for the bond to the panels cabinet. The bonding conductor was sized as if it was a main bonding jumper.
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Tom Horne

 

Thanks. I am aware of the one wire per terminal rule. But I will be surprised if I can find a ground bus that is listed for use in a nearly 40-year-old fuse panel.

 

I would just like to make sure I understand this thread.

If you add a bus to your main electrical cabinet, it would be wise to connect it to the main grounding bus with a bare wire. The bonded cabinet may work by why push it? Is that correct?

 

When you add a buss bar to a panel cabinet it is best to use OEM parts. When these are not available you must pay particular attention to bonding the buss bar either to the neutral buss or to the enclosure cabinet or to both depending on what role the buss bar is to play and whether the enclosure contains the service disconnecting means. The main message is that you should not depend on a field devised mounting system to serve as a bonding means for the added buss bar. The means that you use to bond the new buss bar to another buss bar or to the metallic enclosure cabinet should be by means of a listed lug or a conductor sized as a main bonding jumper.
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Tom H