Adding a ground bar to subpanel

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  #1  
Old 03-04-16, 12:31 PM
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Adding a ground bar to subpanel

I've been reading for over an hour and can't seem to find the answer to:

I am converting a main panel to a sub panel and will need to separate the neutrals and the grounds by adding a ground bar. But how do I attach the ground bar without it touching any metal of the breaker box since that would ultimately connect to neutrals and grounds? I figured I'd drill two holes to hold the ground bar (which may not be the solution, please let me know).

FYI, I am doing this because I bought a house with 2 main panels right next to each other. One panel has the 100 amp service wire coming into it and then there is 8/3 copper wire stacked into the main lug feeding the other main breaker box which has a 100 amp main breaker! I'm going to run 2 gauge Aluminum off a 100 amp breaker from the main panel to fix it as the least expensive option.
 
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  #2  
Old 03-04-16, 12:37 PM
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The existing neutral/ground bar needs to be isolated from the panel and becomes just a neutral bar and is not grounded to the panel. There should be a grounding strap to be removed from the neutral bar that grounds it to the case. The new ground bar is then bonded/grounded to the panel.

The max breaker size you can use to protect #2 Al as a feeder to a sub-panel is 90A.
 
  #3  
Old 03-04-16, 01:13 PM
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With that short of a run..... just use #2 copper wire. Connect the two panels with a short nipple.
 
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Old 03-04-16, 01:14 PM
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There is no grounding strap; just one bar is in this box. It could be from the 1970's or 1980s. I'll get a photo.

OK, so is the existing (and only) neutral/ground bar already isolated?

Also, My local electrical inspector told me I could use 2 gauge Al to run to the 100 amp main.
 
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Old 03-04-16, 01:17 PM
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OK, so is the existing (and only) neutral/ground bar already isolated?
No.... it most likely has a long screw that goes thru it into the metal panel. That screw would need to be removed. We could tell from the picture you post.

Are you using a cable or the nipple method to connect the panels ?
We try to use copper as much as possible for reliability.
 
  #6  
Old 03-04-16, 01:44 PM
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If these photos are too small, here are links to them:

http://www.ad26.com/panel1.JPG
http://www.ad26.com/panel2.JPG
http://www.ad26.com/panel3.JPG


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Last edited by tony17112acst; 03-04-16 at 02:17 PM.
  #7  
Old 03-04-16, 02:02 PM
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Good pictures. We need one of the bar that isn't covered by wiring.

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  #8  
Old 03-04-16, 02:08 PM
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OK, I think I know what you guys mean about the neutral being isolated. Please take a look at the 7 photos above (if you see fewer, then refresh your screen - hit F5 - because I added some later).

I see that the only bar is resting on plastic stabilizers which prevent it from touching the box and I don't see any screws that connect it to the metal box.

I still have the following questions:

(1) Do you think from the photos that the only existing bar is already isolated ...and ready for subpanel neutral status (I just want to be sure neutral is isolated and ground is connected, right)?

(2) If I add a ground bar (purchased from a big box store), is it my goal to then be sure it IS connected to the metal box to be sure the box is grounded?

(3) What is the nipple method?
 
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Old 03-04-16, 02:13 PM
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P.S. The Inspector told me I could use #4 copper or #2 aluminum for the 100 amp subpanel. Since Lowes and Home Depot doesn't sell 4 gauge copper in a 4-wire sheathing, I'd have to purchase separately and create my own conduit (so I hear), so getting aluminum (in stock) seemed like the cheaper/easier way to go and still be in compliance (as the inspector actually recommended).
 
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Old 03-04-16, 02:20 PM
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Yes... that bar in your picture is isolated from the box and will become your neutral bar.
You will add a new bar screwed thru the metal pan for the grounds. The bar will come with it's own self tapping screws.... use them.

#2 service cable is rated for 90A.

The nipple method is a piece of pipe or conduit between the two boxes and then individual wires are used.

Remember..... the service wiring in the top of the main breaker cannot be turned off without removing the meter.
 

Last edited by PJmax; 03-04-16 at 05:00 PM.
  #11  
Old 03-04-16, 02:25 PM
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Oh, so the new grounding bar's screws will connect it to the box ...OK, that's what I was looking for!

OK ...thanks everyone for your input!! I think it'll be an easy job ...assuming I pull the meter before starting! I really appreciate it!

P.S. I just realized that whoever installed that parallel main panel never grounded it since the only bar in it is isolated!
 
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Old 03-04-16, 02:37 PM
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P.S. The Inspector told me I could use #4 copper or #2 aluminum for the 100 amp subpanel.
Your inspector is wrong.

For 100A feeder to a sub-panel you need #3 Cu or #1 Al. The only way #4 Cu or #2 Al is allowed by the NEC is as a 3 wire service that serves as the main power feeder to the dwelling. NEC 310.15(B)(7). The sub feed is sized from Table 310.15(B)(16).
 

Last edited by pattenp; 03-04-16 at 03:07 PM.
  #13  
Old 03-04-16, 03:58 PM
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Pulling a meter is not a diy jobh. You do not have the training or protectIive gear. Also some power companies consider opening their property a criminal act.
 
  #14  
Old 03-04-16, 04:29 PM
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I just wanted to point out something I see in the picture.
Is that old breaker panel Siemens? It appears all breakers except main and red one is replaced with new Siemens.

While, it probably will work fine it is code violation to use breakers other than approved to use with the panel.

Only UL Classified breakers may be used as replacement breaker with listed (by the manufacturer of the breaker) panels.
As far as I know only Eaton UL Classified breakers are readily available. (In fact, I haven't seen any other brands)
 
  #15  
Old 03-04-16, 05:02 PM
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It's allowed to use #2 aluminum on service feeders. That would be from the power company/service head to the meter and the meter to the main panel.

But #1 must be used from a main panel to a subpanel for 100A. Figure that one out.

If you use the #2 cable you must use a 90A breaker.
 
  #16  
Old 03-17-16, 12:12 PM
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OK, today I completed the subpanel conversion and I did end up ordering 3-3-3-5 copper cable to run from the 100 amp breaker to the subpanel. Thanks everyone for the advice and for the reference to the table!
 
  #17  
Old 03-17-16, 01:28 PM
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Good job. Thanks for letting us know the outcome.
 
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