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We’ve replaced our furnace and a/c - which resulted in changes to the wiring from the furnace to the subpanel. The prior furnace was wired to a 240v subpanel with no neutral, which I assume was okay because it was electric resistant. With the new furnace only needing 120v, the installer decided to not add the neutral which I believe is against code.

At the main panel, the furnace is utilizing a 100amp two-pole breaker, which probably isn’t necessary at this point either.

How can I fix this? Both the main and subpanel are ITE panels. And before anyone asks, yes I know the circuit breaker being used in the subpanel is not compatible as well. Plenty of work to be done!

subpanel

isherwood
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RCC
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If everything (there is only one thing) on this subpanel is 120V, install a separate neutral bus bar and use the unused feeder as neutral. Leave the grounds the way they are. In the main panel you just move the same feeder wire to the neutral bus. Hopefully it can reach. And your two-pole breaker can be left alone unless you need the space back for something else.

Alternately, if this breaker does not also function as the required local disconnect for the furnace, you could remove it. Take one of the 20A breakers from this box, put it in the main panel, use the feeder wires as a normal 20A branch circuit to this location and use this box as a junction box. You may need some special connectors to connect the heavy wire to the #12, but it will simplify things.

jay613
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If you convert this to a 120V panel, then adding a neutral is exactly what you are doing. It's the only possible way to make it a 120V panel, since 120V requires neutral to exist.

Now, your panel currently has a neutral bar, which is being misused as a ground bar because it was originally installed as hot-hot-ground and it wasn't being used as a neutral bar. Now you need it for that.

So install an accessory ground bar - the panel labeling will list which models of bar are made to fit pre-drilled sites around the panel. Move the grounds to it, emptying the neutral bar.

If the bare wire can't reach the ground bar, then obtain a suitably sized bare lug, drill a hole with a #21 drill bit NOT on a knockout, and use a self-tapping 10-32 NF screw to mount the lug to the panel.

Remove any neutral-ground bond and pick a hot wire to become neutral, and move that wire to the neutral bar. Mark it with white tape (legal since the wire is #4 or larger).

This panel actually has 4 spaces, but because 2 of the breakers would be upside down, the upper spaces cannot be used except in Canada. Also note that this panel has a Square D HOM and Eaton BR breaker. Those are not allowed in the same panel. Figure out if this is a Square D or Eaton panel, and get or keep the correct breaker.

If you need to power both remaining breaker spaces, you will need to pigtail the remaining hot wire to both lugs. The least bad way to splice is a 3-port Polaris connector of the smallest size allowed for the wire size. This will NOT be cheap and most likely your better option is to remove this panel from the wall and install a 6-space or larger panel. Spaces are cheap, so I would go with a 12-space unless you are constrained for space, then consider a CH or QO 8-space panel.

Harper - Reinstate Monica
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You have conduit for the wires, so pulling a neutral should not be that hard. If the conduit is metal, then do not need a ground wire, the conduit will be the ground path. I am unsure if a bare neutral can touch a metal conduit by code, since only at main panel is neutral and ground bonded.

You also need a ground bus to separate ground and neutral in that panel. A ground bus should be inexpensive.

Cannot read the gauge size of the wire, but it must be 12 gauge on a 20 amp breaker. If 14 gauge you must use a 15 amp breaker or rewire to 12 gauge, if the furnace calls for a 20 amp breaker.

crip659
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