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02-24-2009, 11:38 PM   #1
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## Sub panel wiring question

I posted about this topic on here before and was given this diagram

http://www.diychatroom.com/attachmen...-thru-lugs.jpg

What I need to ask is that my sub panel, has 3 lugs, 2 H and 1 N & a Ground lug. So my sub panel has 3 3/8 lugs, 2 H and 1 N. The diagram has the N from my MAIN panel going to the ground in the sub, however that doesnt take into account my 3/8 N lug on my sub panel.

Any help is appreciated!

My initial assumption is as follows, in case any one wants to confirm

Run my 4/0 Alum. accordingly 2H 1N and then run a ground wire from the main panel ground bus to the sub panel ground bus.

Last edited by mntnvew; 02-24-2009 at 11:45 PM.

02-25-2009, 12:10 AM   #2
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Quote:
 Originally Posted by mntnvew I posted about this topic on here before and was given this diagram http://www.diychatroom.com/attachmen...-thru-lugs.jpg What I need to ask is that my sub panel, has 3 lugs, 2 H and 1 N & a Ground lug. So my sub panel has 3 3/8 lugs, 2 H and 1 N. The diagram has the N from my MAIN panel going to the ground in the sub, however that doesnt take into account my 3/8 N lug on my sub panel. Any help is appreciated! My initial assumption is as follows, in case any one wants to confirm Run my 4/0 Alum. accordingly 2H 1N and then run a ground wire from the main panel ground bus to the sub panel ground bus.
Whenever you feed a 240v sub panel, you need to run a 4 wire feed. H,H,N,G.

Beyond that, I am a bit confused as to what your trying to ask.

Jamie

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Jamie Dolan - Neenah, WI
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 02-25-2009, 06:38 AM #3 Electrical Contractor     Join Date: Apr 2008 Location: Chester, VA. Posts: 1,054 Rewards Points: 510 You need(ed) to run a 4 wire SER cable from your feed through to your sub panel.
 02-25-2009, 10:00 AM #4 UAW SKILLED TRADES     Join Date: Jan 2007 Location: Kansas Posts: 5,341 Rewards Points: 2,652 The diagram is based on prior 2008 code cycle and 3 wire feeds being acceptable. If I remember correctly the main panel is outside on a pole and your running to a pole barn to another panel. NO other metal water pipes or the like to that pole barn. A 3 wire feed with main bonding jumper installed at the sub-panel would be fine and you would not use the ground lug. The diagram is showing the main bonding jumper installed (green dot) so that bar is actually neutral and ground bonded which is required if 3 wires are used. However if the distance is close there is never anything wrong with running 4 wires, but it may not be required by code. Just be sure you do not bond the neutral to ground by not installing the main bonding jumper. If you can post a few pictures of the inside of your sub panel or give us the model and maker we can tell you how to do a 4 wire feed with neutral and ground separated. __________________ " One nice thing about the NEC articles ... you have lots of choices" Stubbie Last edited by Stubbie; 02-25-2009 at 10:05 AM.
02-25-2009, 10:15 AM   #5

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Quote:
 Originally Posted by jamiedolan Whenever you feed a 240v sub panel, you need to run a 4 wire feed. H,H,N,G. Beyond that, I am a bit confused as to what your trying to ask. Jamie
Jamie the only time this is required is

1.) Your on the 2008 code cycle

2.) Your running to a detached structure from the service and you have a water pipe or the like connecting the dwelling with the service equipment to the detached structure.

3.) The service equipment is in or attached to the same building as the sub-panel.

I believe this poster is in a rural area of Montana and no inspections are required so it is likely legal to do 3 or 4 wires to the sub-panel because his main panel (service equipment) is on a post outside but not attached to the barn. It's also very close if I remember correctly.
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02-25-2009, 10:22 AM   #6
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Quote:
 Originally Posted by Stubbie If you can post a few pictures of the inside of your sub panel or give us the model and maker we can tell you how to do a 4 wire feed with neutral and ground separated.
Here is the feed thru lugs on the main panel:

http://i405.photobucket.com/albums/p...npanellugs.jpg

Here is another picture but zoomed out a bit:

http://i405.photobucket.com/albums/p...panellugs2.jpg

Here is a picture of the spacing between the main panel on its 4x4 pt posts and the barn sidewall. The interior panel is placed at the same height on the inside of the wall directly behind this section of sidewall.

http://i405.photobucket.com/albums/p...ngfrombarn.jpg

And lastly, here is a picture of the interior (sub) panel.

http://i405.photobucket.com/albums/p...bpanellugs.jpg

Any insight is GREATLY apprecaited!

Last edited by mntnvew; 02-25-2009 at 04:22 PM.

 02-25-2009, 04:23 PM #7 Member   Join Date: Mar 2008 Posts: 114 Rewards Points: 75 pictures posted!
 02-25-2009, 04:35 PM #8 Member   Join Date: Mar 2008 Posts: 114 Rewards Points: 75 So is this accurate? http://i405.photobucket.com/albums/p...s-feedthru.jpg Notice the red H's and N. This is OUTGOING to the sub panel. -------------------------------------------------------- And then here is the sub panel feed wire placement. http://i405.photobucket.com/albums/p...dplacement.jpg --------------------------------------------------------- So there is NO ground between the two?...??... Should I still drive the green bonding screw into one of the ground bars in the sub (interior) panel? Or am I completely off and I SHOULD have a ground between the two? The guy at the big box store, said ALWAYS run ground between the two so I bough some aluminum ground wire in black plastic in case it is the best solution. I just dont always trust the folks that work at the big box stores as they would be making more money as an electrician if they knew it all
 02-25-2009, 07:37 PM #9 UAW SKILLED TRADES     Join Date: Jan 2007 Location: Kansas Posts: 5,341 Rewards Points: 2,652 Ok I had to leave and was gone most of the day. You have the connections for hot and neutral correct at both panels. You are very close from the service to the subpanel so might as well run a ground. Make it a #6 copper or a #4 aluminum. The bar on the right in your sub-panel image is the ground bar connect to that big lug on the bottom with the ground wire from the outside meter main. The other 2 bars on either side of the busses are your neutral bars. Do not install the green screw this will keep the neutral and ground separate. At the meter main connect to the feeder ground to the neutral/ground bar they are one and the same. You do not need a ground rod at the sub-panel only at the meter main. Connect the hots and neutral as your diagram shows. And make freakin sure the main is off when you connect your wiring. Double check for voltage at those lugs. __________________ " One nice thing about the NEC articles ... you have lots of choices" Stubbie
02-26-2009, 01:28 AM   #10
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Quote:
 Originally Posted by Stubbie Jamie the only time this is required is 1.) Your on the 2008 code cycle 2.) Your running to a detached structure from the service and you have a water pipe or the like connecting the dwelling with the service equipment to the detached structure. 3.) The service equipment is in or attached to the same building as the sub-panel. I believe this poster is in a rural area of Montana and no inspections are required so it is likely legal to do 3 or 4 wires to the sub-panel because his main panel (service equipment) is on a post outside but not attached to the barn. It's also very close if I remember correctly.
Sorry about that. I am kind of stuck in 4 wire mode and since it is required in 2008, I just tend to always think in terms of 4 wire setups now.
Jamie
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02-26-2009, 08:23 PM   #11
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Quote:
 Originally Posted by Stubbie Ok I had to leave and was gone most of the day. You have the connections for hot and neutral correct at both panels. You are very close from the service to the subpanel so might as well run a ground. Make it a #6 copper or a #4 aluminum. The bar on the right in your sub-panel image is the ground bar connect to that big lug on the bottom with the ground wire from the outside meter main. The other 2 bars on either side of the busses are your neutral bars. Do not install the green screw this will keep the neutral and ground separate. At the meter main connect to the feeder ground to the neutral/ground bar they are one and the same. You do not need a ground rod at the sub-panel only at the meter main. Connect the hots and neutral as your diagram shows. And make freakin sure the main is off when you connect your wiring. Double check for voltage at those lugs.
Stubbie, Since I am not using the bonding screw, do I have to run a jumper from the right ground bar, over to the one not in the picture, but on the left side of the interior panel to have it grounded correctly?

It makes sense to me sine that left ground bar is attached to anything but the panel back.

Thanks!

02-26-2009, 08:40 PM   #12
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Quote:
 Originally Posted by mntnvew Stubbie, Since I am not using the bonding screw, do I have to run a jumper from the right ground bar, over to the one not in the picture, but on the left side of the interior panel to have it grounded correctly? It makes sense to me sine that left ground bar is attached to anything but the panel back. Thanks!
If they are both ground bars they should be bonded to the panel and no jumper is needed. You can test continuity between ground bars to be sure.
Jamie
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02-26-2009, 10:32 PM   #13

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Quote:
 Originally Posted by mntnvew Stubbie, Since I am not using the bonding screw, do I have to run a jumper from the right ground bar, over to the one not in the picture, but on the left side of the interior panel to have it grounded correctly? It makes sense to me sine that left ground bar is attached to anything but the panel back. Thanks!
I take there is another bar to the left like the one on the right that is out of the picture. If that bar is mounted to the metal of the panel like the one to the far right then no jumper is required. The metal of the panel bonds the two bars. You can use either one to connect your grounds to...... all neutrals (whites) of your branch circuits go to the two bars left and right of the busses. Just do not install the green screw that would bond the neutral to the panel metal.
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03-02-2009, 12:28 PM   #14
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## All Set!

Many thanks to all, specially Stubbie. Barn is all wired up and everything is KICKING! I have 8 circuits so it is WAY over wired but hell, I can always add wherever I want and never have to touch the panel again

Thanks again!

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