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Old 05-09-2011, 09:32 PM   #1
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Adding subpanel next to main box


I am in the process of adding a subpanel because my main box is full. By design, I will have the garage and basement running from the subpanel.

I would like to run 100amp service to my subpanel. I have 200amp service to the house. I will have a 50amp circuit for my welder, 30 amp for garage, and whatever else for the basement. I have the subpanel mounted and a 100amp breaker to install in the main box.

My questions are this (any help would be appreciated):

1) What gauge will I need to run from my main box to my subpanel to support 100amp?

2) Will this cable need to be in conduit for this run between boxes?

Here is what my arrangement looks like:

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Old 05-09-2011, 09:51 PM   #2
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Adding subpanel next to main box


You will need to use #3(i beleive that is the same in USA as Canada) .

If this was my install I would put a short piece of EMT in between the sub and the main. You probably would have to take the sub off the wall to do this but that doesn't look like it would be to hard. This will give you a nice clean install.

You could also use NMD90 or AC90 in between the two panels.

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Old 05-10-2011, 09:51 AM   #3
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Adding subpanel next to main box


My local Lowes and HD do not carry cable of that gauge... I'm guessing I need to contact an electrician or something?

When you say #3, that is copper, correct?
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Old 05-10-2011, 11:10 AM   #4
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Adding subpanel next to main box


#3 copper wire and a 6" long 2" diameter galvanized nipple. Put the nipple between the panels and use individual THHN wire. You can buy THHN every where. You also need four 2" lock nuts and two plastic bushings.
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Old 05-10-2011, 11:13 AM   #5
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Adding subpanel next to main box


use three # 2 and one #8 green for ground.if they don,t have #2 in white,tape the neutral white.needs to be in conduit.use a seperate ground buss bonded directly to sub panel.neutral goes to isolated buss in sub panel.un less you go to electric supply,#3 is hard to find.only need 1 1/4 conduit.

Last edited by oleguy74; 05-10-2011 at 11:16 AM.
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Old 05-10-2011, 02:11 PM   #6
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Adding subpanel next to main box


When you say "if they don,t have #2 in white,tape the neutral white," that means the physical color of the sheathing?

I'm assuming that is for code, correct?
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Old 05-10-2011, 03:43 PM   #7
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Adding subpanel next to main box


yes, the neutral must be white, the two hots are usually black and red, but they're not required to be marked differently
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Old 05-18-2011, 09:07 PM   #8
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Adding subpanel next to main box


I relocated my subpanel because the holes for my galvanized nipple weren't lined up.

I opened the subpanel, and I'm a bit confused. I don't see a ground bar anywhere...



Am I correct that the bar in the box is the neutral and that there is no ground bar?

Do I need to purchase a ground bar to add to this box? If so, is there any special instructions other than screwing it to the panel?
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Old 05-18-2011, 09:22 PM   #9
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Adding subpanel next to main box


yes you do.
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Old 05-18-2011, 09:26 PM   #10
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Adding subpanel next to main box


Correct, there is no ground bar currently.

http://www.homedepot.com/Electrical-...atalogId=10053

This should work, it mounts to the two holes on the left side of the can
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Old 05-19-2011, 02:26 PM   #11
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Adding subpanel next to main box


Sweet, I'll try to grab one on the way home. Since the new sub panel location is a lot lower on the wall (from the main floor floor joists) than originally intended, do I need to add a board above it clasp wiring to, or can I just clasp it near the joists and allow it to "dangle" down to the sub panel?

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Old 05-19-2011, 02:30 PM   #12
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in my opinion you need some plywood fromsub pnl up.wire needs to be supported.
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Old 05-20-2011, 01:14 AM   #13
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Adding subpanel next to main box


Quote:
Originally Posted by oleguy74 View Post
in my opinion you need some plywood fromsub pnl up.wire needs to be supported.

+1 they should be in a conduit of some sort too depending on local code but that's beside the point.

You can use aluminum wire as well if you cant find copper...I believe you can use #2 alw as long as its XHHW

Look for a local electrical distributor, they should have it at a way lower cost than lowes or hd
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Old 05-20-2011, 08:54 AM   #14
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Adding subpanel next to main box


Quote:
Originally Posted by oleguy74 View Post
use three # 2 and one #8 green for ground....
If he upsizes to a #2, then the ground would also have to be upsized to a #6. See 250.122(B). Copper wire sizes here.

Quote:
Originally Posted by D5T_Designs View Post
....You can use aluminum wire as well if you cant find copper...I believe you can use #2 alw as long as its XHHW....
A #2 XHHW AL conductor is only rated for 90 Amps, since the terminations are limited to 75C. IF using Aluminum conductors, then a #1 would be the minimum size for 100 Amp capacity.
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Old 05-20-2011, 10:30 AM   #15
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kbsparky.just a point of view,table 250.122 says #8 good for 100 amps for a egc.also table 250.66 also says for service conductors #2 copper #8 copper is used.i think in this situiation,in creased in size doesn't apply.so basicly if the OP said he used #2 copper to begin with you would not have said to increase egc.like i said not arguing just a point of view.I would have used #6 myself.

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