? about attaching large ground wire to ground bar

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Old 03-13-09, 12:48 AM
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? about attaching large ground wire to ground bar

In trying to clean up my old panel (sqaure D QO), I noticed that my air handler with emergency back up heat had its ground connected a little differently. It is wired with #4 SEU. There are two pairs of ground wires. If you take both pair and wrap them all together, they will not fit into the ground bar. So the two pair were put into the ground bar separately. Is this allowed? I was at HD and tried to find a lug kit. I ended up buying one --neutral lug kit--QO70AN . but the instructions say "when load center is NOT used as service equipment (Neutral Assembly is NOT bonded or grounded)" Install neutral lug ONLY in neutral bar..." My panel does not have the neutral and ground bonded IN THE PANEL because they are bonded in the disconnect outside by the meter. So they say "neutral assembly is NOT bonded or grounded"--I am confused because my neutral assembly is bonded, just not in that panel? But even if you get by that one and say they mean bonded in the panel itself, then you still can't use it cause it says can only be used on neutral bar? THey didn't have any that said for use on ground bar.

I guess the question is can I use this to connect to ground bar so that I can get all that ground wire connected under one lug? Or is it OK to leave the way it is?

Since I am going to be connect my subpanel soon, I need to know cause it will be with #3 SER and that ground wire will certainly not fit under one lug in current set up (if that is correct size for 100A as someone on forum said--I thought had to go to #2 since #3 is only rated to 95Amps but was told since no 95amp breaker OK to step up to 100amp)
 
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Old 03-13-09, 08:12 AM
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First, I wish to apologize. I believe I was the one to tell you about bumping the 95 amp to 100. While this is true I was using the copper side of the table at the 60 degree. If you are using SER (which is aluminum) you will have to use #2 as you first thought.

Sorry for any confusion.

As far as the ground lug, you can just get a single lug large enough and bond (screw) it to the case of your sub panel.
 
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Old 03-13-09, 01:54 PM
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I was using Cu not Al SER. the 60degree derating for the SER puts #3 at 85 and #2 at 95 and #1 at 110. I guess I made mistake somewhere cause Actually I originally thought I needed #1 Cu SER since #2 is not quite 100. so I am OK with #2 Cu SER? the Al also gets derated? if so, don't I need 1/0 AL SER? this is reason I was going with Cu--trying to get 1/0 wire to subpanel would really be a chore. If I could use #2 Cu, that would be much better.

anyway regarding grounding lug, I am not concearned about at subpanel--I am pretty sure I should be OK there as no heavy draw appliances that will have such large wire should be hooked up there and the ground from main panel will already have a lug for it on the ground bar in subpanel. I am concerned about connecting the ground in the main panel? just bond the lug I bought directly to the metal cabinet? or is it OK to attach the lug to the ground bar-which is attached to the metal case (eventhough it says for neutal only?) or is it OK to do it the way it was done. keep the pairs separated and use two of the smaller grounding screws
 
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Old 03-13-09, 02:27 PM
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Originally Posted by hammerash View Post
so I am OK with #2 Cu SER?
Yes. #2 Copper SER rounds up from its 95A rating to a 100A breaker.

just bond the lug I bought directly to the metal cabinet? or is it OK to attach the lug to the ground bar-which is attached to the metal case (eventhough it says for neutal only?) or is it OK to do it the way it was done. keep the pairs separated and use two of the smaller grounding screws
In my opinion any of those options is okay for an equipment ground wire.
 
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Old 03-13-09, 06:36 PM
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thanks guys. think I will leave the heat pump as is and will wait and see about the ground for subpanel after I actually get the wire. Now IPBOOKS you said any option OK for equipment ground so OK for heat pump. what about for the subpanel? Wasn't sure if that was considered EQUIPMENT.

glad to hear that #2 Cu SER will be OK. beats #1! Didn't realize you could round up like that. Don't quite understand why they let you do that but glad you can.
 
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Old 03-13-09, 09:46 PM
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Originally Posted by hammerash View Post
what about for the subpanel? Wasn't sure if that was considered EQUIPMENT.
Yes, the subpanel ground wire is considered an equipment ground.

Don't quite understand why they let you do that but glad you can.
Yes it helps. There is a published list of standard breaker sizes, and rounding up is allowed when calculated ampacity lands between two standard values. There is already quite a substantial safety margin built in to the wire ratings, so rounding up a small amount doesn't make a big difference other than saving a couple bucks in wire.
 
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