Adding sub panel #2, need some advice

[brianstrange]

I'm Building a detached garage, and would like to add a second sub panel (garage) to my service, and need some advice.

Here's what I have (existing):
200 amp service with a small Wadsworth panel.
100 amp breaker feeding a small GE sub panel (4 of 6 breaker spots occupied) This is right net to the main panel.
Grounds and neutrals are shared on both panels
Existing sub panel was fed with two hots and and one heavy ground and neutral wire buss

Here's what I want to add:
I want to send a 50 amp circuit to the detached garage (2nd sub panel).
My preference would be to use a cable that can be used in the house, and directly buried for ease of installation.
If a GFCI breaker is required to feed the 2nd sub panel, I will need to send power from the existing GE sub panel (lack of Wadsworth products)
I do not want to get into replacing the main panel at this time.
I see that there may be an issue with both existing panels sharing grounds


Can someone give me some guidance? The existing work / panels are from the late 70's. I want to do this right, with what I have to work with.

Thanks in advance,
Brian

 

[Aceman]

You need to separate neutrals and grounds in the existing subpanel. Neutrals should be floating and not bonded to the subpanel.

You don't need a GFCI breaker to feed your garage. A standard 2 pole 50 would be fine. This cable can be ran through your home as well as direct buried out to your garage:

http://www.homedepot.com/p/Southwir...rical-Cable-14782703/202316607#specifications

I would highly recommend running conduit out to your garage though. Even if you just use it as a sleeve for the UF cable.

 

[brianstrange]

You need to separate neutrals and grounds in the existing subpanel. Neutrals should be floating and not bonded to the subpanel.

You don't need a GFCI breaker to feed your garage. A standard 2 pole 50 would be fine. This cable can be ran through your home as well as direct buried out to your garage:

http://www.homedepot.com/p/Southwir...rical-Cable-14782703/202316607#specifications

I would highly recommend running conduit out to your garage though. Even if you just use it as a sleeve for the UF cable.

Thank you, 2 more questions.

1) Is the wire you suggested 3 wire, plus ground?
2) Do I need a separate neutral and ground from the main panel to the sub panel? Based on the picture supplied by another member, it shows three, plus ground.

 

[Aceman]

It should be, I wanted to be sure, so I went to Southwire's website and found this:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM138

It seems they make UF with and without a ground. So to be clear, you need 6-3 with ground UF cable. I would assume that's what Home Depot is selling. It's easy enough to take a look when you're in the store.

To answer your second question, you need a neutral and ground.

 

[brianstrange]

It should be, I wanted to be sure, so I went to Southwire's website and found this:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM138

It seems they make UF with and without a ground. So to be clear, you need 6-3 with ground UF cable. I would assume that's what Home Depot is selling. It's easy enough to take a look when you're in the store.

To answer your second question, you need a neutral and ground.

Any suggestions as to the best way to separate the neutrals and grounds on the existing sub? should I just add a wire from the main panel buss (with both neutral & grounds connected) and bring it ti the sub on a new buss touching the chassis, or just add a buss touching the sub panel leaving all grounds in the sub panel touching the panel chassis only?

Thanks again for your help.

 

[Charles (in GA)]

HD does not mention the ground in their specs, however, some of the other numbers are ONLY found on the 3 wire plus ground spec. the size, 1223 mils, the weight per foot .4784 lb is the same as the very bottom one in the Southwire chart linked to above, 478 lbs/1000ft.

Charles

 

[pattenp]

Your existing sub panel should have a neutral bar and a ground bar just as shown in the diagram you posted. The neutral bar should be isolated/insulated from the panel with all neutrals connected to it. The ground bar should be bonded to the panel via a screw or jumper and all grounds should be connected to it. The only place the neutrals and grounds are landed on the same bar is in the main service panel. You may need to buy a ground bar for the sub panel and remove the bonding screw or jumper that bonds the existing bar(s) to the panel and use that bar for all the neutrals. You will then need to move all the grounds to the new ground bar.

 

[brianstrange]

Your existing sub panel should have a neutral bar and a ground bar just as shown in the diagram you posted. The neutral bar should be isolated/insulated from the panel with all neutrals connected to it. The ground bar should be bonded to the panel via a screw or jumper and all grounds should be connected to it. The only place the neutrals and grounds are landed on the same bar is in the main service panel. You may need to buy a ground bar for the sub panel and remove the bonding screw or jumper that bonds the existing bar(s) to the panel and use that bar for all the neutrals. You will then need to move all the grounds to the new ground bar.

I understand all of this, but I'm still unsure about one thing. The current sub panel has a two conductor plus ground coming in. The two hot leads from the 100 amp breaker, and the ground is from the neutral/ground buss from the main panel. Will the new "ground only" buss on the sub panel need a wire from the main panel?

Thanks!

 

[pattenp]

If the existing is a 3 wire feed then you need to add a 4th wire. But if the 3 wire feed is a sheathed cable it will be against code to just add a separate 4th wire. The thing is your setup was most likely to code when the sub was installed so technically you may not have to worry with it. The new sub will need the ground and neutral isolated from each other. If you decide to upgrade the feed to the existing sub you may be better off just replacing the cable that feeds the existing sub. Just let us know what type of feed wire is used to feed the sub. Is it a cable or individual wires through a conduit?

I understand all of this, but I'm still unsure about one thing. The current sub panel has a two conductor plus ground coming in. The two hot leads from the 100 amp breaker, and the ground is from the neutral/ground buss from the main panel. Will the new "ground only" buss on the sub panel need a wire from the main panel?

Thanks!

 

[brianstrange]

If the existing is a 3 wire feed then you need to add a 4th wire. But if the 3 wire feed is a sheathed cable it will be against code to just add a separate 4th wire. The thing is your setup was most likely to code when the sub was installed so technically you may not have to worry with it. The new sub will need the ground and neutral isolated from each other. If you decide to upgrade the feed to the existing sub you may be better off just replacing the cable that feeds the existing sub. Just let us know what type of feed wire is used to feed the sub. Is it a cable or individual wires through a conduit?

It's cable. It's only a 2-3' run at best.

 

[pattenp]

I'll assume it is SER or SEU cable, so you just need to buy a piece of 4 conductor SER if you want to upgrade the existing sub panel to have an isolated neutral.
SEU

SER

It's cable. It's only a 2-3' run at best.