Ground buss bar and common buss bar - Chevelle Tech
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post #1 of 14 (permalink) Old Oct 15th, 19, 3:51 PM Thread Starter
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Ground buss bar and common buss bar

This welder/garage wiring project got me thinking and I'd like to learn something here. Was it at one time common practice to bond both the white common wire and the bare or green ground wire to the same buss bar? When did this change and why? Not trying to stir anything up just trying to learn here and if my assumptions of the common and ground bonding in the past are wrong that's ok. Once again TIA Pete

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post #2 of 14 (permalink) Old Oct 15th, 19, 5:35 PM
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Re: Ground buss bar and common buss bar

At least here in Mass, in a main panel fed from the street, the ground and neutral bus bars are bonded together and you can put ground or neutral for any circuit in either bus bar.

But, in a sub-panel fed from a main panel, code specifies the ground and neutral have to be separated in the sub-panel and you use an individual bus bar for neutral and another for ground within the sub-panel.

Note this is from when I wired my house 20 years ago and dealt with the electrical codes and inspectors to get everything up to code. Things may or may not have changed since then.

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Originally Posted by no1dc View Post
This welder/garage wiring project got me thinking and I'd like to learn something here. Was it at one time common practice to bond both the white common wire and the bare or green ground wire to the same buss bar? When did this change and why? Not trying to stir anything up just trying to learn here and if my assumptions of the common and ground bonding in the past are wrong that's ok. Once again TIA Pete
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post #3 of 14 (permalink) Old Oct 15th, 19, 6:19 PM
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Re: Ground buss bar and common buss bar

The neutral wire (or center tap of the transformer) comes into the house through the power provider at the meter and is the return path for current to flow. It is connected to the metal box neutral terminal strip. The neutral terminal strip is also connected to your earth ground, a 3' rod driven into the ground by your power box. Neutral (the white insulated wire)is the return path of all your electrical circuits, ground (green uninsulated wire)is the safety that trips the breaker in case of the hot wire (black insulated wire) coming in contact with metal trips the breaker and prevents your body in case of contact with that metal becoming the return path of an a/c circuit.

In other words without the ground say the black comes into contact with the outlet box, the outlet is connected to a metal appliance like a washer machine, if a person touches the machine their body becomes the return path for current to flow and bad things happen. All metal power panels and sub outlet boxes have an uninsulated ground wire to prevent shock or injury.

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post #4 of 14 (permalink) Old Oct 15th, 19, 6:34 PM Thread Starter
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Re: Ground buss bar and common buss bar

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Originally Posted by lucifershammer View Post
At least here in Mass, in a main panel fed from the street, the ground and neutral bus bars are bonded together and you can put ground or neutral for any circuit in either bus bar.

But, in a sub-panel fed from a main panel, code specifies the ground and neutral have to be separated in the sub-panel and you use an individual bus bar for neutral and another for ground within the sub-panel.

Note this is from when I wired my house 20 years ago and dealt with the electrical codes and inspectors to get everything up to code. Things may or may not have changed since then.
Is the 100amp panel that is 40' away in my basement considered a subpanel? If so then am I supposed to have the neutral and ground on separate bus bars? That's going to be fun and a mess if that's the case.

Now I know the garage panel is considered a subpanel and am going to isolate the neutral and ground to separate bus bars. Bought a bus bar this morning to install tonight.

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1970 Chevelle 350cu w/ th350, 750 edel carb, perform intake and lopey cam of unknown specs which produces low vacuum 7-9", otherwise stock motor.
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post #5 of 14 (permalink) Old Oct 15th, 19, 7:55 PM
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Re: Ground buss bar and common buss bar

NEC says the neutrals and grounds are connected to each other ONLY in the first panel or disconnect (if one exists) electrically down stream from the meter where green ground wires, bare ground wires and white neutral wires can be on the same bar but wires of different types or size can not be under the same screw.

Most later panels do have two separate bars and normally electricians do put all the green/ground wires on one bar and all the white wires on the other bar but they don't have to do so.

A new panel comes with a green screw in a bag to ground the one bar to the box IF needed (one bar comes not connected to the box)

If the second panel's power in your house is being fed off of the entrance cable from the meter rather than a breaker in the first panel, it wouldn't be considered a sub panel.

My code book is getting pretty old now (I don't even know if I can find it) but i'm sure the codes were probably always the same.
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post #6 of 14 (permalink) Old Oct 15th, 19, 8:04 PM Thread Starter
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Re: Ground buss bar and common buss bar

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Originally Posted by Dean View Post
NEC says the neutrals and grounds are connected to each other ONLY in the first panel or disconnect (if one exists) electrically down stream from the meter where green ground wires, bare ground wires and white neutral wires can be on the same bar but wires of different types or size can not be under the same screw.

Most later panels do have two separate bars and normally electricians do put all the green/ground wires on one bar and all the white wires on the other bar but they don't have to do so.

A new panel comes with a green screw in a bag to ground the one bar to the box IF needed (one bar comes not connected to the box)There was a green screw but no bar. I purchased one this morning so I can separate the neutral and ground wire in the garage box(subpanel)

If the second panel's power in your house is being fed off of the entrance cable from the meter rather than a breaker in the first panel, it wouldn't be considered a sub panel.
It is not fed from a breaker so that means it's not considered a subpanel

Thanks you Dean and everyone for that information.

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1970 Chevelle 350cu w/ th350, 750 edel carb, perform intake and lopey cam of unknown specs which produces low vacuum 7-9", otherwise stock motor.
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post #7 of 14 (permalink) Old Oct 15th, 19, 8:08 PM
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Re: Ground buss bar and common buss bar

No bar? or no second bar.

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post #8 of 14 (permalink) Old Oct 15th, 19, 11:14 PM
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Re: Ground buss bar and common buss bar

If it's the main panel OR main disconnect the neutrals and grounds can go to the same ground/neutral bar any panel or 120/240 volt disconnect or sub panel after the main means of disconnect that has any 120 volt circuit where the neutral is needed has a floated or isolated neutral bar and the ground bar is bonded to the box with a code approved green screw, ground rods in Fl. used to be 1 rod 8' long and tied to water pipe with unbroken (1 wire) to main panel but now I believe it's 2 8' rods a min of ??? feet apart, I've been out of electrical a few years, my friend/partner 37 yr union Jman died 2016, national electrical code applies everywhere but some municipalities overlook things, be safe, fire inspectors after a fire can tell your homeowners ins. investigator it wasn't done right or per code, CYA IMHO


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post #9 of 14 (permalink) Old Oct 16th, 19, 9:25 AM
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Re: Ground buss bar and common buss bar

Green or grounding is NOT a current carrying conductor, white, neutral or grounded is a current carrying conductor..

You keep them separate in case of a neutral failure because if you didn't, every metal cabinet in the house with a three prong plug could become energized..

Back in the 70s, they had a trick called nick the neutral to pass inspection. They would bond the grounding to the grounded.. Crazy dangerous!!
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post #10 of 14 (permalink) Old Oct 16th, 19, 10:58 AM
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Talking Re: Ground buss bar and common buss bar

Green wire goes behind the wall to the shower arm.





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post #11 of 14 (permalink) Old Oct 16th, 19, 12:38 PM Thread Starter
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Re: Ground buss bar and common buss bar

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Originally Posted by Dean View Post
No bar? or no second bar.
No second bar. Box came with neutral bus bar and I purchased a bus bar yesterday and installed it this morning for the grounds. As a safety precaution I think I'm going to add a ground rod to the subpanel as well.

Member# 1097
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67 std Camaro conv, 1978 Corvette, 03 Silverado, 13 Sonata Hybrid

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post #12 of 14 (permalink) Old Oct 16th, 19, 12:51 PM
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Re: Ground buss bar and common buss bar

You don't need a ground rod.
Just don't put the screw in the neutral bar and ground it to the box

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post #13 of 14 (permalink) Old Oct 16th, 19, 1:04 PM
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Re: Ground buss bar and common buss bar

I just did the same thing. Had to buy a second bar for grounds. take the long green screw out of the neutral bar and toss it in the trash (and by that i mean the drawer in the tool chest with misc fasteners i 'might need' someday) I ran 2-2-2-4 wire from a 100amp double pole breaker in my basement to the 100amp square d box in the garage.

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post #14 of 14 (permalink) Old Oct 16th, 19, 4:55 PM Thread Starter
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Re: Ground buss bar and common buss bar

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Originally Posted by joeyv69ragtop View Post
I just did the same thing. Had to buy a second bar for grounds. take the long green screw out of the neutral bar and toss it in the trash (and by that i mean the drawer in the tool chest with misc fasteners i 'might need' someday) I ran 2-2-2-4 wire from a 100amp double pole breaker in my basement to the 100amp square d box in the garage.
There is no green screw on the neutral bus bar. The bar rests on a plastic base. I added the ground bus bar and utilized the green screw that came with the box to secure it to the box.

Member# 1097
1970 Chevelle 350cu w/ th350, 750 edel carb, perform intake and lopey cam of unknown specs which produces low vacuum 7-9", otherwise stock motor.
67 std Camaro conv, 1978 Corvette, 03 Silverado, 13 Sonata Hybrid

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