2

Existing doorbell transformer in 1950s era California house is sitting in open on a wood shelf in unfinished garage, supplied by non-metallic fabric-jacketed, plastic insulated 2-conductor cable in good physical condition. No ground, no conduit, no strapping, no junction box. I am replacing the transformer with a higher VA model for video doorbell, and wish to make the install better.

Replacement transformer will be mounted on knockout in a 4x4 metal junction box secured to framing, with existing 2-conductor ungrounded cable entering jbox via NM cable clamp. Because of cramped area in/around service panel, ground will be separately supplied to jbox via wire clamped on to Grounding Electrode Conductor.

Question: Can I extend this circuit from the new grounded jbox using metal conduit + THHN hot and neutral wires, or do new outlets supplied by extension have to have standard ground-with-conductors in same raceway all the way back to the service panel? That is, does the 2-wire + separate ground routing for the existing wiring from service panel to jbox prevent further extensions?

4
  • As far as I understand, metal conduit equals a ground wire. I have read newer code allows for a separate added ground to circuits without ground. Extending the circuit should be good, grounding the whole house with one 14 gauge ground wire to GEC, not so good.
    – crip659
    Sep 7, 2023 at 20:42
  • 1
    @crip659 Grounding a few extra 20A outlets with a 10 gauge ground wire to GEC :)
    – Armand
    Sep 7, 2023 at 21:01
  • 1
    Any chance of replacing the existing cable with three conductor cable? Do you know what size it is?
    – JACK
    Sep 7, 2023 at 21:36
  • @JACK Not at this point. Trying to break/make connections inside the untouched-since-1968 service panel is not something I want to rush into.
    – Armand
    Sep 8, 2023 at 1:15

1 Answer 1

2

You can do this

NEC 250.130(C) explicitly states "branch-circuit extension" as one of the things that can have its ground connected to a retrofit EGC, so your plan with the retrofit EGC is fine.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.