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Old 10-20-2012, 08:04 PM   #1
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Question about garage sub panel.


Hello folks. I installed a 100 amp sub panel in my garage running from my home 200 amp panel.

The garage square d sub panel does not have a separate ground bar.

The sub panel came with a green bonding screw. If I use the screw can my grounds and naturals run on the same bar?

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Old 10-20-2012, 08:24 PM   #2
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Question about garage sub panel.


No, go buy a ground bar.
Did you run a ground wire to the panel?

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Old 10-20-2012, 08:37 PM   #3
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Question about garage sub panel.


You do not bond the grounds and neutrals at a sub panel. If this sub is in a structure not attached to the house, you need to drive 2 ground rods and run minimum #8 to the ground bar.
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Old 10-20-2012, 08:46 PM   #4
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Question about garage sub panel.


I did run the ground from the house panel to the garage panel.


In the house panel the ground has its own bar.


So I got 4 wires coming from the house. 2 hots from the 100 amp breaker, neutral and ground.
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Old 10-20-2012, 09:27 PM   #5
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Question about garage sub panel.


Do not bond grounded conductors with the grounding conductors at the sub-panel - only at your main panel feeding the subs.
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Old 10-20-2012, 09:54 PM   #6
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Question about garage sub panel.


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Originally Posted by wonderd View Post
I did run the ground from the house panel to the garage panel.


In the house panel the ground has its own bar.


So I got 4 wires coming from the house. 2 hots from the 100 amp breaker, neutral and ground.
You still need ground rods at a detached structure.
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Old 10-20-2012, 11:21 PM   #7
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Question about garage sub panel.


So I need 1 or 2 ground rods? Also do I still need a seperate ground bar for inside the panel?

Would 1 ground rod be okay being I have the ground wire from the house also

Last edited by wonderd; 10-20-2012 at 11:49 PM.
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Old 10-21-2012, 12:51 AM   #8
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Question about garage sub panel.


1 ground rod if you can prove it provides a resistance of less than 25 ohms. Otherwise 2.
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Old 10-21-2012, 01:56 AM   #9
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Question about garage sub panel.


I went through the same thing.......

At your main panel....ground and common are tied together.

At your sub....they are NOT tied together.

You run a ground wire from your main to the sub.....

As Techy said....if you can 'prove' your ground resistanc is less than 25 ohms, you only need one rod......BUT....the effort to prove the resistance is more work than just driving a second rod into the ground....at least 6' from the first one.

One last thing....if your sub does not have a main disconnect, you can not have more than 6 breakers.
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Old 10-21-2012, 02:03 AM   #10
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Question about garage sub panel.


Okay I have one more question about the bonding of neatral and ground.

I probably should have mentioned that in my house box, the neutal and the ground are not bonded. I have been doing a lot of reading that says a detached garage should have seperate neutrals and grounds if the main panel is bonded. But in my case it is not.

Should I still isolate my neutral and ground in my sub panel, or should it be bonded?
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Old 10-21-2012, 02:04 AM   #11
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Question about garage sub panel.


Okay I have one more question about the bonding of neatral and ground.

I probably should have mentioned that in my house box, the neutal and the ground are not bonded. I have been doing a lot of reading that says a detached garage should have seperate neutrals and grounds if the main panel is bonded. But in my case it is not.

Should I still isolate my neutral and ground in my sub panel, or should it be bonded?
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Old 10-21-2012, 02:28 AM   #12
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Question about garage sub panel.


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Originally Posted by wonderd View Post
Okay I have one more question about the bonding of neatral and ground.

I probably should have mentioned that in my house box, the neutal and the ground are not bonded. I have been doing a lot of reading that says a detached garage should have seperate neutrals and grounds if the main panel is bonded. But in my case it is not.

Should I still isolate my neutral and ground in my sub panel, or should it be bonded?
At the sub...neut and ground are NOT bonded....and you need to bond your neut and ground at your main panel.

One very important question....is the garage attached or detached?

If attached....then you don't need the ground rods.....
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Old 10-21-2012, 02:52 AM   #13
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Question about garage sub panel.


Its detached, I am not going to touch anything in the main box as it was installed by a professional. My question is can my sub box ground/neut still be isolatd like the main?
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Old 10-21-2012, 04:58 AM   #14
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Question about garage sub panel.


ddawg16 was wrong to suggest bonding your main panel. The bond can also happen at your meter/main disconnect, depending on local rules. The key is it can only happen once. And it can never happen at a sub panel.

Last edited by Glennsparky; 10-21-2012 at 05:09 AM.
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Old 10-21-2012, 09:16 AM   #15
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Question about garage sub panel.


Quote:
Originally Posted by Glennsparky View Post
ddawg16 was wrong to suggest bonding your main panel. The bond can also happen at your meter/main disconnect, depending on local rules. The key is it can only happen once. And it can never happen at a sub panel.
I assumed that his main sub was also the disconnect.....

But you are correct....the bond can happen at only one spot.....

So...if the main panel is also his disconnect/meter....it needs to be bonded.....if not....no bond...

Me? I would be measuring the voltage between ground and neut by now...

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