I replaced my doorbell transformer last night with a higher power one in preparation for a video doorbell. When I took the old transformer out (it was attached to my main panel via knockout and piggy backed onto the office circuit) I noticed the ground wire was clipped. I assume it was being grounded by being secured to the metal panel.

The new transformer has a plastic knockout connection. When I installed the new one I didn’t cut the ground but I did put the ground with the neutral wire under the neutral wire nut. The wire was short so there is a jumper from the bonded neutral bar up to the transformer. I assumed this would be okay as both wires would land on the bonded neutral bar on the panel anyways. Is this okay? Or should I separate the white and green wire and run a separate green wire to the neutral bar?

old doorbell transformer

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    Don't land ground and neutral together. The bars in the panel are a special case. Did this transformer come with any installation instructions?
    – KMJ
    Commented Dec 19, 2023 at 2:10
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    Okay I will separate the neutral and ground. Yes the instructions were straightforward and said to connect each of the wires. I just assumed since the ground and neutral were bonded at the panel that I could be lazy and not put another wire in for the ground. My bad. Thank you! Commented Dec 19, 2023 at 2:17

1 Answer 1


Assuming I understand this correctly, that you connected neutral and ground together in a wire nut inside the main panel, What you did was almost certainly safe but not according to code. According to code, the only place neutrals and grounds can be mixed together is on the neutral bar of a true main panel. Which gives you two choices:

  • Extend neutral and ground separately to the neutral bar
  • Extend neutral to the neutral bar and ground to the ground bar (assuming there is a separate ground bar).

The concern is that while right now this is a true main panel, in the future it could become a subpanel to either a bigger main panel or to a "meter main" to satisfy newer code to provide an outside disconnect. The more of a mess your panel is, the harder it will be to separate grounds and neutrals if you ever need to. During my heavy-up, my electrician avoided putting grounds on the neutral bar as much as possible, though there were a few old cables where putting the ground on the neutral bar avoided having to extend the ground wire, so he put those on the neutral bar.

Or just trade it in for a transformer with metal.

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    Yes that’s exactly what I did. I have some bare copper wire I can run to extend the ground down to the bar. I’ll keep the neutral on the existing white wire. I will do that when I install the doorbell tomorrow. Thank you. Commented Dec 19, 2023 at 2:42

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