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The picture below shows the electrical panel in a single-family detached home that my wife and I are in the process of purchasing. The home inspector flagged an issue here with the neutral and ground wires being connected on the same bus bars (left and right), suggesting that neutrals and grounds should be separate and (electrically) insulated from each other.

Electrical panel in home built in 1988

The seller had his building engineer (not a certified electrician) look at it and claims that they cannot separate neutral and ground because the two bus bars are electrically connected through the back of the panel. (A bit difficult to see in the picture, I have not been able to verify myself yet.)

The house was built in 1988 and was inspected at that time. It is located in Maryland, USA. This is the only panel in the home, and it is in the unfinished part of the basement near where I see the service entering the home on the outside. As far as we know, there have not been any issues with the electrical since then.

What should we do? Is this a real safety concern? If you had to (and it is proper to) separate neutral and ground here, how would you do it?

I have done some research on my own, but I am not an electrician. I see most advice is that it's always a good idea to separate neutral and ground except where they connect at the "main service panel". I'm not sure if this is the main service panel or not. I've read some other advice that some systems are designed to have neutral and ground electrically connected like this and it would be a bad idea to separate them in that case. Any help is much appreciated!

May be related to these other questions:

Bonding Neutral and ground in a service panel

Main Panel with separated neutral and ground

Separating neutral and ground in panel

Electrical panel ground issue

Update 2019-10-25:

I was able to get into the house today and get a lot more pictures. This appears to be the main panel: I do not see any other breakers/switches between here and where the service enters the house. There also appears to be a screw bonding the neutral bus bar to the encasement (just to the right of the bus bar on the left). I gather that this satisfies the two conditions specified in Retired Master Electrician's answer below. Here are more detailed pictures of the panel:

Detail image showing screw going through neutral bus bar and into encasement

Entire panel, showing only one main switch

  • Hello, and welcome to Home Improvement. Nicely-written question; let's see if you get any good answers. And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Oct 24 '19 at 12:42
  • Thanks! I'll check it out. – Chad Lieberman Oct 24 '19 at 14:00
  • Where is the main circuit breaker (first thing past the meter)? Is that it? – Harper - Reinstate Monica Oct 24 '19 at 19:12
  • @Harper: As far as I can tell, this is the main panel. I do not see any other switches to cut off service between here and where it enters the house. – Chad Lieberman Oct 25 '19 at 15:36
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In residential services only, you can attach grounding conductors and neutral conductors at on the neutral bus, but it must meet certain requirements. First the main breaker in the panel must be the first means of disconnect from the meter (no separate main breaker). Second the neutral bus must be bonded to the Panel (look for the green screw or a lead going to the encasement).

Any panel after that is considered a sub panel and must have a separate neutral and ground bus.

I will also say that this could change depending on the interpretation of the AHJ. So it's always a good idea to check in with them before proceeding with any argument.

Hope this helps.

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  • Thanks for your response! I will have an opportunity to check into the two prerequisites you raised tomorrow, and I will report back, probably with more pictures. – Chad Lieberman Oct 24 '19 at 13:57
  • I verified these two conditions. See edit to question above. Accepting your answer now. – Chad Lieberman Oct 25 '19 at 15:48
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Your main panel only, is required to have a neutral-ground equipotential bond. The purpose is to clamp system voltages so they stay within 200 volts or so of ground, so the insulation works.

They could use a more complex system, but the simplest is to simply wire one of the conductors to ground and then call that neutral.

The ideal N-G equipotential bond is a #4 bit of wire between neutral and ground buses, with enough back clearance to get a clamp meter around it.

However there's nothing wrong with using a special screw to ground the neutral bus. There is also nothing wrong with throwing both grounds and neutrals on the same bus, though this would be quite bad to do in a subpanel.

So your inspector is mistaken about this being a redflag. However he would be right to spot a couple of things.

  • Double-tapping the neutral bar lugs actually is a red flag, unless the panel instructions say double-tapping is OK. I have seen instructions that require single-tap of neutral, and single or triple tap of ground, but no double tapping. (that sounds like something they compromised on with UL).
  • Runting off the neutral wires so they can only reach the neutral bar is legal, and some say encouraged by the 110.12 requirement for "neat", but it makes a big mess when those wires must be extended to reach a GFCI or AFCI breaker. Best practice is to leave hot and neutral both long enough to reach any breaker space in the panel.
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  • Thanks for your answer, @Harper. I appreciate the extra detail you provided. I may look into having an electrician fix it up in accordance with best practices, but for now I think it seems acceptable enough to not hold up the purchase of the property. – Chad Lieberman Oct 25 '19 at 15:51
  • There won't be a panel that lets you double-tap neutral lugs for two different circuits -- that's forbidden by NEC 408.41 (and probably by the UL 67 standard loadcenters/panelboards are listed to, as well). – ThreePhaseEel Oct 26 '19 at 1:46

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