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Old 03-11-2010, 03:56 PM   #1
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Basement Sub-panel neutral/ground confusion


First I'd like to thank all those who have posted a heck of a lot of valuable information on this subject already. Your efforts are certainly appreciated.

I've got a 150A main breaker panel mounted to a concrete block basement wall. It only has 2 spaces vacant. After reading NUMEROUS sub-panel related posts here, I thought I had it all figured out. I bought a 100A main with 20 spaces yesterday ($49 and included 8 15A breakers).

My confusion arose after re-reading this thread:

Sub-panel for basement (Full Kitchen, bath, theater)

In particular, the photo of 'Abs777' panel looks very much like mine, with one huge difference. Mine does not have a ground(ing) bar mounted to the metal case. It is numbered "1" in his excellent photo. There is no number "1" in my new sub-panel.



My sub-panel's two neutral bars (numbers "3" and "2") look exactly like the photo, complete with the large black insulated copper wire jumpering the two neutrals together.

My question is, since in a sub-panel the neutral and ground CAN NOT be bonded together, I think I'm suppose to remove the large black 'jumper' wire between the two neutral bars. Then, use the LEFT neutral bar as my neutral and the RIGHT neutral bar as my ground after torquing the GREEN bolt down, so that it makes contact with the metal case thus making it a ground?

Does this rambling make any sense?

Any help deeply appreciated...

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Old 03-11-2010, 04:06 PM   #2
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Basement Sub-panel neutral/ground confusion


Yes, that is one way that a panel can be setup as a sub panel
Other option is to buy a grounding bar & install
All depends upon how many circuits you will be running & if there will be enough locations to land a neutral on one side

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Old 03-11-2010, 04:44 PM   #3
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Basement Sub-panel neutral/ground confusion


Thanks for your speedy reply, Dave!

I assume the big box store where I purchased the panel would sell the grounding bar & mounting screws? I looked again at my new sub-panel and it indeed appears to have two drilled and tapped holes for mounting a grounding bar exactly where the one in the photo is mounted.

I'm using #2 aluminum entrance cable and the large lug at the top of the grounding bar in the photo looks like it would be more 'user friendly' as far as connecting a fat #2 wire.
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Old 03-11-2010, 05:01 PM   #4
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Basement Sub-panel neutral/ground confusion


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Originally Posted by rstain View Post
Thanks for your speedy reply, Dave!

I assume the big box store where I purchased the panel would sell the grounding bar & mounting screws? I looked again at my new sub-panel and it indeed appears to have two drilled and tapped holes for mounting a grounding bar exactly where the one in the photo is mounted.

I'm using #2 aluminum entrance cable and the large lug at the top of the grounding bar in the photo looks like it would be more 'user friendly' as far as connecting a fat #2 wire.
You could also just remove the tie-bar and install a larger lug(made by siemens) on to the left hand buss(#3).
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Old 03-11-2010, 07:53 PM   #5
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Basement Sub-panel neutral/ground confusion


The big box stores sell the ground bars. If you decide to install one, you have to make sure the two existing bars (which will be for neutrals) is NOT bonded to the metal case of the panel, and that the new ground bar IS.

Use a continuity tester between each neutral bar and the ground bar, you should not have continuity between either of them and the ground bar, but you should have continuity between the two neutral bars. You can test this before running any wires or installing any breakers.
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Old 03-11-2010, 08:49 PM   #6
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Basement Sub-panel neutral/ground confusion


Remove the green screw and you will not bond the neutral.
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Old 03-12-2010, 07:31 AM   #7
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Basement Sub-panel neutral/ground confusion


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Originally Posted by rstain View Post
Thanks for your speedy reply, Dave!

I assume the big box store where I purchased the panel would sell the grounding bar & mounting screws? I looked again at my new sub-panel and it indeed appears to have two drilled and tapped holes for mounting a grounding bar exactly where the one in the photo is mounted.

I'm using #2 aluminum entrance cable and the large lug at the top of the grounding bar in the photo looks like it would be more 'user friendly' as far as connecting a fat #2 wire.
This site is great and the knowledge here is invaluable. I have included a chart that Scuba_Dave posted about cable size. I thought I had used the wrong cable when I first wired mine and don't want you to go through the same thing. You said you were using #2 AL, what kind are you using?

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Old 03-12-2010, 08:20 AM   #8
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Basement Sub-panel neutral/ground confusion


What size breaker are you feeding the basement panel with?
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Old 03-12-2010, 06:56 PM   #9
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Basement Sub-panel neutral/ground confusion


Wow, thanks to all who have chimed in! Your help is certainly appreciated.

I will be mounting my new sub-panel about 3' to the left of my existing 150A main in an unfinished basement in which I'm adding woodworking equipment, shop lights, outlets.

I went to both competing big box stores, and while both sell Siemens panels they only offer Homeline (square-d) add-on ground bars which means I'll have to drill two new holes in my new panel to mount the bar. I bought one and a large lug add-on that I'll mount at the top.

I'm going to come off a 100A breaker in the main using the following: Butler/Holley Alumaflex - Service Type XHHW-2 CDRS 600 volts - 3 CDR AWG2 - 1 CDR AWG4.

I'll be using Noalox anti-oxidant everywhere the aluminum contacts steel.

I realize this is overkill (100A feed for sub-panel) for what I really need or will use, but the difference in price for less capacity was fairly negligible.
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Old 03-12-2010, 07:10 PM   #10
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Basement Sub-panel neutral/ground confusion


That cable is only rated for 75 amps.
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Old 03-12-2010, 07:32 PM   #11
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Basement Sub-panel neutral/ground confusion


When I bought my panel I also bought a double pole 20A breaker to to feed my new table saw. The motor tag reads: 3hp - 220V - 12.4A

It has a NEMA 6-15P 3 conductor plug as seen here:

http://www.generatorjoe.net/html/web...quailplug.html

I have a couple of questions concerning this. First, should I have bought a 15A breaker (instead of the 20A) for the circuit that will feed the saw?

What gage Romex and number of conductors should I use to the NEMA 6-15R receptacle since the motor is rated at 12.4A? I mean, it's only a 3-prong plug, where/how does this table saw get its chassis ground?

The 6-15R recepticle only has 3 screw lugs. 2 hots and a netural,,, or 2 hots and a ground? (the 3rd screw is green)

Edit: After reviewing the picture of the 6-15R at the above link I now see that tiny "G" which I guess means that it's 2 hots and a ground (and no neutral connection). So would I just run 2 wire with ground Romex (12AWG)?

Last edited by rstain; 03-12-2010 at 08:12 PM.
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Old 03-12-2010, 08:10 PM   #12
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Basement Sub-panel neutral/ground confusion


Quote:
Originally Posted by rstain View Post
When I bought my panel I also bought a double pole 20A breaker to to feed my new table saw. The motor tag reads: 3hp - 220V - 12.4A

It has a NEMA 6-15P 3 conductor plug as seen here:

http://www.generatorjoe.net/html/web...quailplug.html

I have a couple of questions concerning this. First, should I have bought a 15A breaker (instead of the 20A) for the circuit that will feed the saw?

What gage Romex and number of conductors should I use to the NEMA 6-15R receptacle since the motor is rated at 12.4A? I mean, it's only a 3-prong plug, where/how does this table saw get its chassis ground?

The 6-15R recepticle only has 3 screw lugs. 2 hots and a netural,,, or 2 hots and a ground? (the 3rd screw is green)
14/2 wg. Two hots, 1 bare equipment ground. reidentify white conductor with amagic marker or tape to indicate that it is a hot conductor. 15 amp two pole breaker. There is no neutral.

See also posting # 10 above.

Last edited by brric; 03-12-2010 at 08:14 PM.
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Old 03-12-2010, 08:24 PM   #13
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Basement Sub-panel neutral/ground confusion


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14/2 wg. Two hots, 1 bare equipment ground. reidentify white conductor with amagic marker or tape to indicate that it is a hot conductor. 15 amp two pole breaker. There is no neutral.

See also posting # 10 above.
Thanks, brric, that's what I'll go with then especially since it's only a 30' run...

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