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Old 07-31-2006, 12:46 PM   #1
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A few Questions on Sub panels


I want to put a 40amp sub panel in my garage. In the subpanel I will use 2 breakers (1) 20amp for the recepticals, and (1) 15 amp for the light circuit and opener receptical.

My questions is:

1... To feed the panel, in the main breaker box, would I use a 40 amp breaker, and feed my 8 ga wire off this to the 40 amp breaker in the subpanel? (not sure if sub panels has 1 or 2 hot bus bars)

2 As for grounding, would I be able to ground the sub panel in with the main ground bus bar in the main panel in the basement, or would i need to drive in a seperate ground rod outside the garage for the sub panel?


Last edited by stagger19; 07-31-2006 at 12:49 PM.
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Old 07-31-2006, 02:21 PM   #2
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A few Questions on Sub panels


Since 60 amp is the smallest common size pane that you will find, why not use that and run number 6 wire using a 60 amp breaker.

You could still use the 40 amp breaker and numbrer 8 wire if you want with the 60 amp panel. It is up to you. You will need a two pole breaker for the main panel. The sub panel has two hot bars.

As for the grounding. Is your garage attached or detached. This is a very important issue regarding grounding the sub panel and if to tie the neutral and ground together at the sub panel.

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Old 07-31-2006, 02:26 PM   #3
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A few Questions on Sub panels


Quote:
Originally Posted by jwhite
Since 60 amp is the smallest common size pane that you will find, why not use that and run number 6 wire using a 60 amp breaker.

You could still use the 40 amp breaker and numbrer 8 wire if you want with the 60 amp panel. It is up to you. You will need a two pole breaker for the main panel. The sub panel has two hot bars.

As for the grounding. Is your garage attached or detached. This is a very important issue regarding grounding the sub panel and if to tie the neutral and ground together at the sub panel.
So if I wanted to use a 60 amp breaker, I would run 6-3G, or if i wanted to only use a 40AMP Sub panel, I would run 8-3 with ground right?

The garage is detached, about 20ft from the house.

OBTW, I found a great site on wiring the subpanel if anybody has questions. This site seems pretty good on the details involved.

http://www.hammerzone.com/archives/e...1/overview.htm

Last edited by stagger19; 07-31-2006 at 02:48 PM.
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Old 08-01-2006, 04:16 AM   #4
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A few Questions on Sub panels


Quote:
Originally Posted by stagger19
So if I wanted to use a 60 amp breaker, I would run 6-3G, or if i wanted to only use a 40AMP Sub panel, I would run 8-3 with ground right?
You will need a main breaker panel for the sub panel so that you have a disconnect at the remote building. You will need a ground rod at the garage as well.

Your wire sizes are right, but weather or not you need a four conductor or three conductor depends on if there are any other metal paths between the two buildings. Phone, water, gas line etc.
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Old 08-01-2006, 07:49 AM   #5
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A few Questions on Sub panels


Quote:
Originally Posted by jwhite
You will need a main breaker panel for the sub panel so that you have a disconnect at the remote building. You will need a ground rod at the garage as well.

Your wire sizes are right, but weather or not you need a four conductor or three conductor depends on if there are any other metal paths between the two buildings. Phone, water, gas line etc.
Ok, thanks. I thought i had to go with a main Lug and a separate disconnect? Doesnt the ground and Neutral have to be physically seperate in the sub panel, and connect together ONLY in the main panel? If i go with a main Breaker type box, is there a way to isolate the grounds and neutrals??

If i can go with a main breaker type panel, that will make it much easier, as I wont need to have 2 boxes out there.

There is no other metal lines running out to the garage, however, when I run the power cables, i want to run in separate conduit, a wire for the alarm system to put the garage on a zone in the main alarm system, and a cat5 cable. Would this be considered a metal path back tot he house??? if so, would this result in a seperate ground rod needed outside the garage? Would I need to ground in both places, or just in one or the other?

Thanks in Advance....

Last edited by stagger19; 08-01-2006 at 08:58 AM.
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Old 08-01-2006, 09:47 AM   #6
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A few Questions on Sub panels


You will need the ground rod for a seperate building or structure no matter what. The only exception is for light poles like in store parking lot.

The issue about additional metal paths is about if the neutral can be used as the ground wire from the original building or if a seperate equipment ground needs to be used. Even that small alarm cable counts as a metal path and therefore you need to run a ground wire with your feeder wires, and seperate the neurtals and grounds at the second building or structure (the garage)

When you buy your main breaker panel, ask if the neutral and ground bars can be seperated. some panels have a bar on each side of the breakers with a cross bar that is removable tieing them together. They also have a way to bond the enclosure to one of the bars.

Sometimes you can remove the tie bar, put the enclosure bond on one the ground bar and wire the neutral to the bar that is not bonded.

Sometimes you have to purchase a seperate ground kit and mount the ground bar that comes with it directly to the back of the enclosure.

The kind salesman at any electrical supply house can help you figure out what you need if you tell them that your grounds and neutrals need to be seperate. You may get lucky and find someone as knowledgeable at the big box store.
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Old 08-01-2006, 10:04 AM   #7
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A few Questions on Sub panels


Thanks Jwhite, you made it very easy to understand.
Yeah if i can use a Main breaker panel and seperate the Neutral from the grounds, it will make it much easier as I can install a main breaker as the main disconnect, instead of using a main lug panel and a seperate disconnect next to it.

I really appreciate your help!

Thanks Again.....

-Rich


Last edited by stagger19; 08-01-2006 at 10:08 AM.
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