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Ground Bar Neutral Bar

Why separate the ground bar from the neutral bar in a sub-panel?

Hi Russ,

Thank you for your question regarding the separation of the ground bar from the neutral bar in an electrical sub-panel, it is our pleasure to help.

The difference between a ground wire and neutral wire is often misunderstood.  The problem primarily comes from the inappropriately named “neutral” wire.  There is nothing neutral about a neutral wire.  It is a current-carrying conductor, just like a hot wire and has all the potential for danger and should be treated with the same respect. 

Consider the schematic for a flash-light.  Your typical flashlight consists of a battery, a switch, a few wires, possibly a fuse, and a light bulb.  Let’s ignore the switch, as it doesn’t relate to the point we are trying to make.  In a flash light without a switch, you would see a black wire running from the battery to the light bulb, and a white wire running back from the light bulb to the battery.  The black wire would represent the “hot” wire, and the white wire would be our “neutral”.  The green ground wire would be tied to the metal case of the flash light and bonded to the battery return terminal via a fuse, and would be an open in regard to the rest of the circuit.

If you were to take a multi-meter and make a few measurements, you would see that the black wire has maximum amperage, and maximum voltage.  The white wire has maximum amperage, and minimum voltage.  The green ground wire would have minimum voltage and minimum amperage.  The important thing to note, is that the white wire has the same amperage as the black wire.

Now, the white wire will have minimum voltage, until you add another light bulb to the circuit.   If you cut the white wire in half, and inserted a second light bulb, the first half of the white wire would now both maximum current and half the voltage.  The second half of the white wire (the piece tied to the battery) would have maximum amperage and minimum voltage.  This could go on for as many light bulbs as we want to add into the circuit.  Any resistance added to the white “neutral” wire, will instantly become part of the circuit and see voltage.  The green ground wire would only come in to play if the black or white wire were to accidentally come in contact with the case.  The electricity would short to the case and travel back to the battery causing a temporary increase in current, which in conjunction with a fuse would stop the flow of electricity.

When we are dealing with an electrical 120-volt circuit, the same thing is true with our neutral white wire.  It only appears to have zero volts because there is no resistance.  If you become part of the circuit, the voltage will form across your body.

Now, in the case of a single-phase electrical subpanel, we know that 100% of the current from the hot-wires will travel on the neutral wires back to the main electrical cabinet.   If we bond the ground wire to the neutral in the sub-panel, current will flow on both the neutral AND on the ground wire.  Which means that if you do not keep the ground wires separate from the neutral wires, you will be allowing return currents to flow on the ground wires back to the main panel.  This is not only bad for obvious safety reasons, but it will also cause problems with GFCI breakers and cause equipment interference issues.  It is also of course a violation of the National Electrical Code (NEC).  You are to have one and only one connection between the ground system and the neutral system, and that is at the first service disconnect.  This is vital for the proper operation of over current protection devices (OCPD) such as fuses and circuit breakers.

We hope you have found this information useful, if you should have any further questions, please do not hesitate to contact us again in the future.

Best regards,

The Engineering Team at E&S Grounding Solutions


Photo credit: E&S Grounding Solutions

8 Responses

  1. Gordon Alexander

    I have a sub panel that is not bonded ,(bonding screw removed)neutral wire connected to neutral bar and ground wire from main panel is connected to the ground bar in sub panel. Why is there continuity? between the neutral bar and the pane?

    1. Marcus Horak

      Because they are bonded together at the main panel. You are closing the loop with you continuity tester at the sub panel.

  2. Mike Kaplan

    Thank you for explaining why to separate the ground bar from the neutral bar in a Sub-Panel.
    Sorry, still do not get it.
    Then why not separate the neutral bar from the ground bar in the main panel?
    If you can explain it in another terms? Thank you very much.
    Mike Kaplan

  3. Sparky Rob

    Nonsense. Separation of neutrals and grounds is nothing more the paralled grounds. Everything in a house panel works fine with everything bonded. The frame of the panel, the meter can, the ground rod, neutrals, grounds ext. Bottom line is you have grounded conductors and ungrounded conductors. All grounded conductors are electrically contected at some point in any system. If there was a risk on the grounded conductor in a residential service .The grounded conductor would be insulated and not bonded to the panel or meter can. To some up the grounds and so called neutral are grounded conductors. They are bonded together somewhere. Whatever amps or volts is pumping through them is pumping through the “one” grounded conductor at the bonded meter AND panel. You could grab that wire and hang from your tongue all day and it would never hurt you. And fuses and breakers including gfcis would function normally.

  4. JC Vasquez

    I am adding a breaker, and have room for it. There isn’t a space on the neutral bar for either the White or Ground wire. What should I do?.

  5. Calhou9n C. Benton

    Your explanation concerning the Neutral and Ground and why they are needed to be separated was really a great piece. I need to explain this to a friend who is adding a panel in his new barn and plans to use ground fault breakers for the work areas that will be on the bare ground. He is going to run triplex underground from his house, which is amply supplied, and has a separate sub-breaker openening for another panel.

  6. In the case of the sub-panel observed above can we assume the larger green stranded wire is attached to the main panel grounding system?….my question is on Residential construction most homes are required to have a main shut-off outside of the structure…turning the inside panel into a sub panel. Is it wrong to just run a second grounding rod/wire to the panel inside of the home or do you still have to seperate neutral and ground bars at that point for everything to be correct? Any information is greatly appreciated.

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