Bonding Question by a Newbie

Franz

Member
Location
SC, USA
Occupation
Retired
I realize many of you are professionals and I am likely to get numerous “Call an electrician…” responses, but I want to understand what I’ve got and best approach to get what I want after modifying existing circuitry. Here’s the existing condition… and yes I have contacted an electrician who is going to come to my location….

At my newly purchased house which we are remodeling (built circa 1968) I have the following set of panel/subpanels:
1 Main/primary/first Square D panel with a 200A breaker - two black 120V lines, one black w white stripe neutral conductor and one black ground wire from the meter directly adjacent. This panel and meter are mounted to an exterior brick wall outside the house, directly opposite a utility room with 3 secondary or subpanels. This panel supplies power to the three subpanels, all of which are Square D QO Load Center catalog number QO 12-24. They each have one black 120V black line, one red 120V line, and one large twisted aluminum wire connected to one (or both?) of the ground and neutral bars which are directly adjacent to one another. The bare aluminum wire runs back to the main panel.

One subpanel is fed by a 125V breaker and only has 120V “mini/narrow” Square D breakers. This subpanel has what appears to be separate but adjacent neutral and ground bars, but all the white neutrals and bare copper ground wires from the circuits are connected to just one of these…it’s packed.

The other two subpanels are each fed by a 100A breaker in the main. They have same black and red 120V lines inbound which have lugs at top and the twisted aluminum wire attached to one or both of the neutral and ground bars which are near the bottom of the panel box. Both of these other two subpanels only have 240V breakers. Each breaker serves an old ceiling mounted radiant heat system above each room. The circuits in these two panels consist of two wire Romex without a ground in the NM cable jacket. Each black and white wire carries 120V to a box and were connected at a controller (rheostat?) mounted in each room. From there the “heat wires” run up to the ceiling where they disappear into the Sheetrock. I presume they attach to a grid/mat embedded in the plaster layer over the Sheetrock. The heat wires and controllers will be removed. These two panels appear to have one green insulated ground wire for each breaker connected to one of the bars. These green wires enter the panel separately from the two wire Romex which connect to each breaker.

Finally, my objectives/questions:
1) I want to convert a number of the existing 240V radiant heating circuits to 120V circuits and use them to minimize the number of outlets/lights/appliances on the existing 120V circuits.
2) Can I use the two existing subpanels which only have 240V breakers by swapping out for 120V breakers? Connect white (now neutral) wire to the unoccupied bar?
3) I’m assuming I (and electrician) must ensure the neutral and ground bars are not bonded in the old 240V panels(?)
4) what about the existing subpanel with only 120V breakers - should we split up the neutrals and bare copper ground wires onto separate bars and ensure they are not bonded?

Appreciate your patience with the lengthy description and any suggestions. Tried to attach photos but couldn’t get it to work.
 
Since you are using an electrician, he will take care of it. But to ease your mind:
1. You can reuse the panel, you cannot use the wiring, ground wires are required now.
2. Same issue.
3. It was legal in 1968, so if left unchanged, you don’t have to do anything. But by changing things, you trigger the need to do it per current code.
4. Same issue.
 
Thank you Jraef for the reply. I have a few more questions:

Can both 240 and 120V be available in the repurposed subpanel?

Regarding the old 240V wiring, my hope was to reuse it by putting it into a junction box in the attic above a couple rooms. Then use new Romex with a ground from the junction box down to the new outlets or to supply power to LED canless lights. If the green insulated wires run to each room, can these be used as the ground wires to a metal junction box?

Even if I use new wire all the way to the repurposed subpanel(s), how is ground and a neutral achieved? Is the twisted bare aluminum the existing ground from the subpanel back to main panel? Will a new neutral heavy wire need to be pulled from the subpanel to the main?

Could the existing red wire in the subpanel be relocated to that panel’s neutral bar and likewise to the main neutral bar if only 120V was be fed to that subpanel?
Thanks again.
 
Update - I was mistaken. The Romex running from the former heating subpanel to the controller metal box does have an insulated green ground wire incorporated into the NM cable jacket. So, I have a ground, a black and a white for each circuit that I want to repurpose.
 
Update - I was mistaken. The Romex running from the former heating subpanel to the controller metal box does have an insulated green ground wire incorporated into the NM cable jacket. So, I have a ground, a black and a white for each circuit that I want to repurpose.
Then you are good to go. Just keep in mind, for 240V heating circuits, White was often used as one of the hots, since the heaters didn’t need a neutral. So you can repurpose it for 120V, OR you can keep using it for 240V, not both.
 
Thanks for the confirmation. Yes they used white as a 120V conductor to the rheostat and then heating system wires (red and black) went up into the ceiling. Will swap breakers and use white as neutral. I’m planning on using these old circuits for overhead lighting in four rooms initially and will then do same in the bedrooms. Each room has one of these old radiant heating set ups with their own wiring and breaker.

Had an electrician come by today. I showed him my panels and overall repurposing idea. He said that in a practical sense he thought I could go with what I have since the existing system was compliant in the past, has been trouble free for decades and that the maximum distance from the furthest subpanel to main is short (about 7-8 feet).

But I want the update to be as close to current code and installation standards as possible, so I’m going to have him install three dedicated grounding wires back to the main panel and also ensure the neutral and grounding bars are not bonded in all three subpanels. Will relocate neutrals and grounds onto separate bars in each.

Thanks again. Great site!
 
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