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Some HVAC people under previous home owners put in a sub panel box and ran the AC as well as some lighting and outlet circuits from the sub panel.

The bus bars on the two sides of the panel box were used for both the neutral and the ground wires just like in the main breaker box.

I assumed that it was right because they were professionals and should have had an inspection for the sub panel and the HVAC. I have been reading about how sub panel boxes should have separate neutral and ground bus bars.

Are there panel boxes which are not designed to be sub panel boxes and should only be used as main breaker boxes? The sub panel looks like the main box except the sub panel did not have a main shut off breaker in the sub panel.

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  • Are you sure they're bonded together? Panels with neutral bars on both side can normally be isolated by removing the jumper that runs between them and them driving a green ground screw thru the bar into the metal chassis on the ground bar side.
    – Brian Duke
    Commented Nov 28, 2014 at 20:52
  • user3623501 asked if the bus bars were bonded together. I am not at the location and cannot look, but I think they are. What I am sure of is that the ground wires and neutral wires are mixed on each bus bar like they are in the main panel. Even if the two bars are not bonded together the ground and neutral have to be on separate bars, don't they?
    – user11933
    Commented Nov 29, 2014 at 22:38
  • @user11933 -- in a subpanel, they indeed do.
    – ThreePhaseEel
    Commented Jan 6, 2016 at 4:19
  • See what happens when you trust some "licensed professional" instead of a DIY forum full of a bunch of dolts on the internet?
    – Billy left SE for Codidact
    Commented Jan 6, 2016 at 7:04

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You are probably in violation of National Electric Code, article 250.32(B)(1) states that the grounded conductor(neutral), shall not be connected to the equipment grounding conductor(ground).

The general rule of thumb is the only point the ground and neutral get bonded together is at the first point of disconnect for any incoming system, be it utility, generator, or some other source. There are a few exceptions for specific situations but none of which I feel apply.

Easiest course of actions is to kill panel, un-bond bars, drive screw through one bar into chassis and make that ground bar, use the other isolated bar for neutral. With no other knowledge of your installation I would advise you be careful of the loose neutrals while making the swap, if any are somehow being used by circuits from the other panel(it happens) they could shock you.

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  • Who the heck downvoted this answer? It's dead on the money as to what needs to happen to fix this mess...
    – ThreePhaseEel
    Commented Jan 6, 2016 at 4:20
  • To eliminate risk of loose / shared neutrals biting you during this work, shut off not just the subpanel, but the main breaker to the entire premises, on the service entrance panel during this work.
    – Billy left SE for Codidact
    Commented Jan 6, 2016 at 19:15

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