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I am adding a 70A 2 breaker subpanel to a shed and will have two (2) 15A circuits. I want to wire from a nearby, no longer used disconnect (230V) that was used for an air compressor. The disconnect is wired from the main from a 30A breaker with 2 hot wires and a ground from main panel. There is no neutral wire at the disconnect. Distance from disconnect to new sub is approx 50'.

Can I power the subpanel with the 2 hot wires and the ground from the disconnect to the new subpanel?

I have added grounding rods into the ground at the shed to ground. Would I bond the existing ground from disconnect to new ground wire from grounding rod by attaching both to the ground bar?

DO I need a neutral wire going to the subpanel?

The subpanel has a neutral and ground bar that are NOT bonded. From each breakers I would run the hot to the outlet and the neutral from outlet to neutral bar??

All help is appreciated. I have searched previous articles and none seem to be exactly on point.

2 Answers 2

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You need a neutral, or a transformer to make a new neutral.

With 3600VA of load, (2x15AX120V) a small, affordable, commonly available 5000VA transformer would do the job.

Feed 240V in one side, pull 240V center-tapped from the other side. That center tap is your new neutral for 120V (and would be bonded to ground.)

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If you have 120V loads, you must have a neutral wire.

If your existing wire is in conduit, pull a neutral.

If it's cable, one of the current hot wires is probably natively white. Remove the hot marking (usually colored tape) on each end and connect the supply end to neutral in your main panel instead of a breaker. You won't be able to supply any 240V loads if you do this, of course.

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