Neutral and ground connected to same bus

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j0796609
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Neutral and ground connected to same bus

Post by j0796609 » Fri Sep 06, 2019 12:51 pm

Hi, i was adding a circuit in my 100 amp subpanel in the garage and i noticed that the ground and neutral wires are all running into the same bus bar.
6 years ago i had an electrician put in a 220v 40 amp circuit along with several 20 amp circuits and he didnt say anything about it, and in fact he ran the ground into the neutral bar on the circuit he added.
My friend that does HVAC says its a bad idea and i should have the whole panel rewired. Other sources online say mixed things.
Who is correct? Run about 70 amps through this panel all day every day for a legal marijana grow.
I dont wanna get zapped or start a fire. Ive not had any problems with it thus far.

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Aaron
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Re: Neutral and ground connected to same bus

Post by Aaron » Fri Sep 06, 2019 4:39 pm

Yes, the neutral and ground only bond together at the service entrance panel. So if you have a sub panel with them bonded together, it should be rewired to isolate them. This usually entails purchasing an additional terminal strip for all the grounds, and attaching it to the back of the panel chassis, there are usually pre-tapped holes for the accessory strip.

The existing neutral strip should be electrically insulated from the panel chassis unless a ground bonding screw was used to bond it to the chassis. This screw should be removed.

Isolate the grounds and neutrals and your panel will be properly wired.

j0796609
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Re: Neutral and ground connected to same bus

Post by j0796609 » Fri Sep 06, 2019 6:01 pm

Why only at the service entry panel?
Is it unsafe the way it is?

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Aaron
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Re: Neutral and ground connected to same bus

Post by Aaron » Fri Sep 06, 2019 7:13 pm

I'm not an electrical engineer so I can't explain the precise electrical theory behind it. But I think it has something to do with channeling all the return current on neutral from the load side of the service entrance panel, because neutral is indeed considered a current-carrying conductor, whereas ground is absolutely ground and nothing other than ground.

Right now you could possibly get shocks if you were to touch the ground, and if you have GFCI receptacles off that sub-panel they would likely malfunction because it would sense residual current on the ground.

Think of a sub-panel as really nothing more than a sort of high-amperage "extension cord" from your service entrance panel, and, like an extension cord or power strip, the neutral and ground are always isolated, just as they are everywhere else beyond any panel. Sub-sub-panels would be the same way... anything downstream from the service entrance panel, the ground and neutral conductors are isolated.

It's the electrical code, it's the right way to do it, and you should correct it.

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emtnut
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Re: Neutral and ground connected to same bus

Post by emtnut » Sat Sep 07, 2019 7:29 am

The whole panel doesn't need to be rewired, just the grounds and neutrals separated.
Not sure where you saw conflicting info online, but sub-panels always have to have them isolated.

Not sure of your location, but in Canada even the main panel needs the separation, NEC allows them to be together in the main panel (only).

There can be a few issues with your setup.
-Having current on the ground wire can zap someone working on the circuit (even with the breaker off)
-The ground wire is there for short circuit protection, and is sized according to the circuit. You can overload the ground (improbable, but not impossible) with the 'extra' ground current.
-Depending on how the house is wired, it can add current to the water pipes. These pipes 'should' be bonded, but even still, you could get zapped when doing plumbing jobs.
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Aaron
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Re: Neutral and ground connected to same bus

Post by Aaron » Sat Sep 07, 2019 2:35 pm

emtnut wrote:
Sat Sep 07, 2019 7:29 am
Not sure of your location, but in Canada even the main panel needs the separation, NEC allows them to be together in the main panel (only).
Really!!

That makes more sense, frankly... seems logical that you'd want that neutral balance back to the transformer instead of being shunted to ground. (Not that I know what I'm talking about.)

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emtnut
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Re: Neutral and ground connected to same bus

Post by emtnut » Sat Sep 07, 2019 3:27 pm

Aaron wrote:
Sat Sep 07, 2019 2:35 pm
emtnut wrote:
Sat Sep 07, 2019 7:29 am
Not sure of your location, but in Canada even the main panel needs the separation, NEC allows them to be together in the main panel (only).
Really!!

That makes more sense, frankly... seems logical that you'd want that neutral balance back to the transformer instead of being shunted to ground. (Not that I know what I'm talking about.)
In both cases the neutral current flows back to the transformer.
The way NEC allows the mixing of ground and neutral in the main panel, some of that current flows through the bonding jumper, and then on to the neutral conductor from the Tx
Not an issue that I can see, but I still find it weird when I see pics of a main panel on the internet with the grounds and neutrals intermixed :shock:

Note for OP, this is the main panel we are talking about, your subpanel should still be separate ;)
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Aaron
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Re: Neutral and ground connected to same bus

Post by Aaron » Sat Sep 07, 2019 10:01 pm

I'll never forget when I was like 10 or 11, watching my Dad opening the breaker panel to install a breaker and him being very amazed and confused to see the neutrals and grounds both terminated on the same strip.

Back in the 1980s, where if something seemed weird or strange you couldn't just look it up on the Internet really quick to see if it was normal or not!

It's remarkable how we take that for granted now.

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