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-   -   Can i add a subpanel fed by 10/2 wire? (http://www.diychatroom.com/f18/can-i-add-subpanel-fed-10-2-wire-7697/)

qst4sno 04-10-2007 07:48 PM

Can i add a subpanel fed by 10/2 wire?
 
Hi there folks, let me set up the situation and then I'll post my questions.

I recently bought a home where the previous homeowner had ran an underground 10/2 line to a detached shed about 100ft from the main home. In the shed the line terminates in a single outlet that I believe has a plug for a compressor on it. The 10/2 line is fed by a single pole 30amp breaker on a subpanel in the garage.

Here's what I want to accomplish:

I'd like to install a 30amp square D subpanel in the shed and have two 15amp circuits coming from it to feed some overhead lights and some basic 110v outlets for power tools etc. etc.

My question is two fold.

1. Can I do it in this fashion?

and

2. If so, the 30amp panel that I have has 2 spaces for the 15amp breakers but it looks like it requires a 3rd line (red?) to provide power to the second breaker. If so, do I need to pigtail two black lines from the main 10/2 feed to provide power to both breakers?

and my final question is.....do I need to add a neutral bar or can i just terminate all the neutral wires together with a wire nut?

Hope this isn't too confusing and I appreciate any and all responses.

nick

joed 04-10-2007 08:00 PM

1. Yes
2. Yes.

3 You need a ground bar and a ground rod.

jwhite 04-10-2007 08:30 PM

If you keep the neutral in the sub panel isolated. (throw away the green screw that came with it) and install a ground bar and ground rod, then feed both legs of the new panel from the same circuit. It all sounds legal.

qst4sno 04-11-2007 08:38 AM

thanks guys. JWhite could you clarify for me, on how to add the ground bar and rod? I'm a little confused with your response. Thanks

jwhite 04-11-2007 07:24 PM

Your sub panel will come with one bar that can be used for either ground or neutral. Since you will have a seperate ground comming from the house, you will seperate the grounds and neutrals in the sub panel.

The bar that comes with the panel will have a green screw that when installed makes the bar a ground bar. Throw this screw away, and buy an extra ground bar. You will now have one bar that is isolated from the metal box (enclosure) and one that is attached directly to the metal enclosure. The one that is isolated is where the neutrals will go. the one that is attached is where the grounds will go.

Next buy a ground rod and get out the sledge hammer. Outside the shed drive the ground rod into the ground. Then run a #6 wire from the ground rod to the panel ground bar.

I know 6 seems big, especially when the size of the circuit is only 10. but the ground rod is to protect against lightning. A short circuit needs to be cleared by a good connection back to the main panel in the house and the transformer serving the system.

RippySkippy 04-12-2007 07:53 AM

Quote:

Originally Posted by jwhite (Post 40589)
.... but the ground rod is to protect against lightning.

I sold a house with a similar setup as the OP and have some basic questions....

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

Also JWhite, I'm not a master anything so I'm looking for clarification here. How does the ground rod from the sub panel protect from lightning? It would seem the path of lightning strike would come from 2 paths, exterior or line.

The line path would be intercepted from the house main, and the exterior would have to have a separate grounding path as the interior and exterior are not directly connected. Assuming that there's a separate ground for the out building, the interior and exterior are still not connected, and the ground rod still doesn't protect from lighting. I'm missing something here...what is it?

jwhite 04-12-2007 08:02 PM

Lightning goes from sky to ground. anything under ground is not suseptable.

sorry spelling.

The wire and ground provide a constant drain. the prevent the lightning from striking, The size has to do with the ammount of drain needed.

jwhite 04-12-2007 08:03 PM

ok i do not know how to explain the lighting well enough ...
I do know what the code says to do.

jwhite 04-12-2007 08:04 PM

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

Isnt that what I told the OP to do???????????????????????????

Louieb 04-14-2007 08:20 PM

Put away the sledge hammer because its not needed This is technically a single circuit feeder and 250.32 Exception allows this !the nuetral and ground must be seperated though.

jwhite 04-15-2007 07:03 AM

Quote:

Originally Posted by Louieb (Post 40996)
Put away the sledge hammer because its not needed This is technically a single circuit feeder and 250.32 Exception allows this !the nuetral and ground must be seperated though.

Not if he runs it to a panel and divides it again further. If that were the case then every feeder is nothing more than a MWBC.

NateHanson 04-15-2007 11:59 AM

Quote:

Originally Posted by RippySkippy (Post 40667)
I sold a house with a similar setup as the OP and have some basic questions....

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

Was your garage attached or detatched from the house?

A separate ground rod is only called for if the subpanel is in a detached structure, as with the OP.

That's my simplified understanding anyways.

RippySkippy 04-15-2007 08:04 PM

Hi Nate, it was a detached garage, with the electricity supplied from the house main. I was all set to do as you said, but the city inspector said no-way, and demanded as I said...dunno...I don't own the house anymore, it was inspected and passed...go figure.

jwhite 04-16-2007 05:26 AM

Quote:

Originally Posted by RippySkippy (Post 40667)
I sold a house with a similar setup as the OP and have some basic questions....

I added the circuit to the garage, and before inspection, I asked specifically about the grounding requirements of the garage. The city inspectors would not allow another ground rod to be included on the house main. They required an isolated ground bar in the new box wired to the neutral that went back to the house main. Was this a safety hazard?

One does not put the added ground rod at the house main. It goes at the sub panel outside the detached structure. Wether to make this a three or four wire feed is another topic.

RippySkippy 04-16-2007 08:57 AM

It was a 4 wire extension.


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