30 amp double pole breaker feeding detached garage?


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Old 10-27-08, 09:47 AM
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30 amp double pole breaker feeding detached garage?

first post here, but I have read and had a lot of questions answered before!

So we are doing a 100% remodel of our house which includes new service (from 100a to 200a) and all new wiring through out. The service transfer as already been inspected and approved, and the overhead line to the new meter and panel has been done. However the old panel fed the detached garage and the main shutoff for it is in the attic (then goes overhead from the house to garage 15' away)
I am needing to run a new line up from the new panel in the basement to this shutoff in the attic. However the existing is stumping me and I am not sure why.
The shutoff in the attic is a 30 amp double pole breaker (a bar accross two throw offs, each labeled 30amp) and then connected to each hot is a twisted #8 wire which then goes outside, through the air and to the garage subpanel. Each has its own #8, and then a white #8 connected to the bus (no ground wire) so 3 wires total. the #8 wire looks to be fairly newer and in great shape. I believe the garage was added in '95.
However moving to the garage the breakers are 3- 15a and one 20 a. so 65a total breakers installed (spots are full). This is where my confusion lies. Is the garage being fed with 30amps or 60 amps? Normally the double pole breaker would be a 30 total (not 30+30) but the fact that they each have their own seperate wire and the garage is at 65amps makes be wonder...

So if i havent confused people enough, then my question is what do i run off of my new main panel? a double 30amp breaker using #8 up to the shutoff or do i run a 60amp breaker using #4 up? Its just under a 50' total run to the shutoff. I am thinking since it is already using #8 I cant run anything larger than a #8 to it correct?
Any help would be greatly appreciated! thanks
 
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Old 10-27-08, 02:12 PM
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from what i have read and gathered, i can run an 8-3 wire from my main panel (40 amp breaker) up to the attic and connect to my existing #8 wires (2 blacks, 1 white) and then attach my ground from the 8-3 to the throw off switch box in the attic. Then my 3 wires run overhead (nometallic connection possible) and to the existing subpanel where my white is connected to my nutural AND ground bar (same bar due to no ground running from the house) with a copper running from the bar to an existing outside ground rod.
i am also thinking that i might want to use a 30 amp breaker instead of a 40 and run 10-3 wire from my main panel to the throwoff in the attic because my overhead outside wire is #8. (sizing down due to cold weather)

does this sound like things are on the right track?
 
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Old 10-27-08, 02:12 PM
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I don't like your description of the overhead conductors going to the garage, without knowing a lot more.

But back to your question. The 2-pole 30-A breakers are for 240-V. The smaller breakers in the garage are presumably serving 120-V branches. Your service to the garage would be described as 30-A, 240-V.
Doug
 
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Old 10-27-08, 02:19 PM
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you dont like the description? What about it can i clarify?

There are 3 total wires running from the garage to the house- 2 are black #8 braided and the 3rd is white #8 braided.
 
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Old 10-27-08, 02:42 PM
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I would get rid of the shutoff in the attic. Splice the wires in the enclosure and be done with it. The feeder circuit breaker in the service panel will suffice as the 'new shutoff.'


What do the wires from the attic shut-off to the overheard wires to the garage look like. Cable? Single conductors?


So long as you don't upgrade the overhead wires, and wiring at the garage, you can leave it as is. You only have four circuit breakers in the garage's sub panel so you have less than the maximum 6 circuit breaker throw rule. You may want to install ground rods at the garage.


Any modifications between the overheard drop from the house to the garage and wiring in the garage will mean you have to adhere to the in-force NEC for your area.
 
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Old 10-27-08, 03:00 PM
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splicing is what i think i will end up doing. currently there is actually a double pole 30A breaker up there. I think i will just remove the breaker and use the existing box as the enclosure and just ground my 10-3 to that.

the wire is 3 seperate twisted wires (6-7 small copper solid to make the 8 size)
 
 

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