40amp subpanel

[metal1313]

i need some guidance here, i would like to FINALLY have real power going to the detached garage. i buried some 1.5in conduit several years ago, but our main box is full, we have 200amps coming in but only a 20slot main box.

we recently replaced the electric dryer with a gas unit so now i have a breaker available to power the garage. i think i need 8gauge wire, with a 10gauge ground. is this correct? and obviously seperate wires are easier to pull, but is there a recomended type of wire to use other than something rated for burial/underground conduit use?

the plan is a 40amp sub, with 1 40amp circut, and 2 20amp. maybe a slightly different lay out but something close to those lines?

fyi going to pull the wires myself and wire up outlets but have an electrician do the actual hook ups

 

[pattenp]

#8 is correct for 40A. You can either pull 8/3 w/ground UF, or 3 #8 and 1 #10 individual THHN/THWN wires. Why only 40A?

I'd do at least 60A to the sub. Use a main breaker panel in the detached garage.



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[metal1313]

Only 10x20 garage no real need for more. It's my parents house and I'll be out soon anyway

 

[theoldwizard1]

What is the total distance from breaker box to breaker box ?

If you are using individual conductors you will have to run the conduit all the way up to the breaker box.

Get a 6 slot, no main, breaker box for your garage. Under $20 at HD

I agree with pattenp. Wire for 60A.

 

[electrican]

#8 is correct for 40A. You can either pull 8/3 w/ground UF, or 3 #8 and 1 #10 individual THHN/THWN wires. Why only 40A?

I'd do a least 60A to the sub. Use a main breaker panel in the detached garage.



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you cant pull romex through a pipe it is not legal

 

[Charles (in GA)]

#8 is correct for 40A. You can either pull 8/3 w/ground UF, or 3 #8 and 1 #10 individual THHN/THWN wires. Why only 40A?

I'd do a least 60A to the sub. Use a main breaker panel in the detached garage.

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you cant pull romex through a pipe it is not legal

Where is that facepalm pic that says "not this $hit again" when you need it???

There is no restriction in the NEC about this. In fact, Chapter 9 has a paragraph that tells us how to determine area of the cord or cable for determining fill in conduits.

You cannot by the NEC put Romex underground, either in or not in conduit, as that would be a wet location that Romex is not rated for. But UF is not Romex and UF is rated for wet location, so there would not be a problem with it being in the conduit.

Charles

 

[pattenp]

Thank you Charles.

Where is that facepalm pic that says "not this $hit again" when you need it???

There is no restriction in the NEC about this. In fact, Chapter 9 has a paragraph that tells us how to determine area of the cord or cable for determining fill in conduits.

You cannot by the NEC put Romex underground, either in or not in conduit, as that would be a wet location that Romex is not rated for. But UF is not Romex and UF is rated for wet location, so there would not be a problem with it being in the conduit.

Charles

 

[pattenp]

Agreed. Use a small main lug panel if you are going to have 6 or less breakers. More than 6 breakers, you need to use a main breaker panel.

What is the total distance from breaker box to breaker box ?

If you are using individual conductors you will have to run the conduit all the way up to the breaker box.

Get a 6 slot, no main, breaker box for your garage. Under $20 at HD

I agree with pattenp. Wire for 60A.

 

[metal1313]

i should mention i do already have a 15amp line to the garage, it is buried under the driveway and i believe that its just uf wire buried under the driveway alone, thats my light circuit. i really only need 30amps to run my welder, dont have a large compressor, no other really high amp tools.

but for 60amps i'd need #6thhn right?

 

[pattenp]

#6 THHN/THWN is okay for 60A. As far as the 15A UF to the garage, that line will need to be abandoned because you are allowed only one power feed to a detached building. You may be able to use the UF as a switch loop for a light at the garage controlled from the house but the power for the light must come from the garage.

 

[electrican]

don't forget a ground rod!

 

[MFortie]

Agreed. Use a small main lug panel if you are going to have 6 or less breakers. More than 6 breakers, you need to use a main breaker panel.

Couldn't he use a main lug panel (for over 6 spaces) and backfeed as long as he uses a hold down clip or screw?

 

[Mustang51js]

Couldn't he use a main lug panel (for over 6 spaces) and backfeed as long as he uses a hold down clip or screw?

Yes he can

 

[pattenp]

Yes, as Mustang has said. But if buying a new panel it doesn't make sense to me to use a main lug panel with a back fed breaker for the main disconnect.

Couldn't he use a main lug panel (for over 6 spaces) and backfeed as long as he uses a hold down clip or screw?

 

[electrican]

I guess you don't care about the ground rod!

 

[pattenp]

Actually he should set 2 ground rods at least 6' apart from each other.

I guess you don't care about the ground rod!

 

[electrican]

you need a !/2 ground rod 8 ft long for a detached building

 

[metal1313]

to me, the ground rod was a given. i already have two, and one of them is in place already.they were a trade when i did some roofing for a local electrician a few years ago, i would have asked his advice and prob had him do the job but he passed about 2 years ago due to an MVA