Need Help Choosing Wire

[Sterff]

Hey guys I need your help. We are about to purchase a new air compressor for our garage. The garage is about 50' from the house but does have a 1 1/4" conduit buried connecting the two. I want to run a line from our home's panel to the attic of our garage where the compressor will be installed.

Since the wire will technically be underground in the conduit, will I need to use a direct burial type wire? Also the total run will be 150' max. Will 10-3 wire work? The compressor requires a 30 amp breaker but, Im kind of concerned about the length of the run. I want to wire it to a quick disconnect box and then to the compressor. Here is a link to the compressor. Most likely it will be purchased at Lowe's though. Thanks

http://www.northerntool.com/shop/tools/product_200365168_200365168

 

[snorky18]

you only need 10-2, not 10-3, since you don't need a neutral.

not sure on the wire type for burial/conduit.

 

[mrb]

does the garage currently have power? If so you cant have two seperate circuits run to a detached structure. You would have to switch to a feeder and subpanel.

 

[ForceFed70]

I would suggest a 50amp subpanel then bring out a 30amp circuit for the compressor.

But MRB brings up a good point. You probably already have electricity in the garage for lights, etc. Do all of the garage circuits run directly back to the house or is there a subpanel in the garage already?

I would reccomend direct burial even tho you are running through conduit. 1.25" should leave lots of room.

If the circuit length is over 100' you will want to upsize the wiring and go with 8ga conductors.

 

[Sterff]

does the garage currently have power? If so you cant have two seperate circuits run to a detached structure. You would have to switch to a feeder and subpanel.

Yes there are already lights and recepticals. By feeder and subpanel, do you mean install a nother panel and then run a dedicated line to the compressor?

I would suggest a 50amp subpanel then bring out a 30amp circuit for the compressor.

But MRB brings up a good point. You probably already have electricity in the garage for lights, etc. Do all of the garage circuits run directly back to the house or is there a subpanel in the garage already?

I would reccomend direct burial even tho you are running through conduit. 1.25" should leave lots of room.

If the circuit length is over 100' you will want to upsize the wiring and go with 8ga conductors.

I would assume they run back to the house. There is no subpanel out there. Currently there are two wires running out there.

 

[Aceman]

Yes there are already lights and recepticals. By feeder and subpanel, do you mean install a nother panel and then run a dedicated line to the compressor?

I would assume they run back to the house. There is no subpanel out there. Currently there are two wires running out there.

That means you abandon the existing wires running out there and run one main feeder to your garage. Install a subpanel, refeed the existing circuits out of it, and then run a circuit to your compressor.

Don't forget to install a grounding electrode, typically rods.

 

[Charles (in GA)]

Yes there are already lights and recepticals. By feeder and subpanel, do you mean install a nother panel and then run a dedicated line to the compressor?

I would assume they run back to the house. There is no subpanel out there. Currently there are two wires running out there.

If by "two wires" you mean two pieces of cable (hopefully not Romex as its not allowed in conduit underground) then that is one too many. You are allowed a house panel to supply a detached garage or accessory structure with only one circuit. It can be a 120v or it can be a 240v but only one circuit. If you need to split up the power in the garage, you need to pull out all existing wires and run one circuit of heavier wire, such as # 6 neutral and two hots and a #10 ground (all THwN wire) with a 50 amp breaker supplying it, and a small circuit breaker panel in the garage, and run all the lights, receptacles, compressor, etc, from there.

Don't forget to install a grounding electrode, typically rods.

Oh yes, that too, forgot. Also need a disconnect at the garage.

Charles

 

[Sterff]

That means you abandon the existing wires running out there and run one main feeder to your garage. Install a subpanel, refeed the existing circuits out of it, and then run a circuit to your compressor.

Don't forget to install a grounding electrode, typically rods.

Ok, I see $ adding up.

If by "two wires" you mean two pieces of cable (hopefully not Romex as its not allowed in conduit underground) then that is one too many. You are allowed a house panel to supply a detached garage or accessory structure with only one circuit. It can be a 120v or it can be a 240v but only one circuit. If you need to split up the power in the garage, you need to pull out all existing wires and run one circuit of heavier wire, such as # 6 neutral and two hots and a #10 ground (all THwN wire) with a 50 amp breaker supplying it, and a small circuit breaker panel in the garage, and run all the lights, receptacles, compressor, etc, from there.


Charles

Alright, currently both wires runnning to the garage are direct burial type wire. One circuit is for the lights and one is for the receptacle. So I take it I should eliminate those, and run out a main line to a circuit breaker panel, then run everything off of it?

 

[Charles (in GA)]

Ok, I see $ adding up.

Alright, currently both wires runnning to the garage are direct burial type wire. One circuit is for the lights and one is for the receptacle. So I take it I should eliminate those, and run out a main line to a circuit breaker panel, then run everything off of it?

That would be code compliant. Leaving those circuits in place and operational whether or not you add a new circuit is not code compliant. Only one circuit allowed between buildings.

Charles

 

[Sterff]

That would be code compliant. Leaving those circuits in place and operational whether or not you add a new circuit is not code compliant. Only one circuit allowed between buildings.

Charles

Why do they only want one circuit? Just wondering.

 

[RangerDaleXp]

#10 would be the minium with a 5% V.L on a 30 amp breaker. But I would run at least #8 if it was me

 

[Charles (in GA)]

Why do they only want one circuit? Just wondering.

It has largely to do with the safety of persons working on the circuits in the future. If you have multiple circuits from another building or buildings(s) and you went to work on the wiring, you stand a chance of encountering hot circuits even though you think the power has been disconnected.

The reference on this is 225.30 however there are exceptions, such as capacity requirements in excess of 2000 ampere, and where buildings are of such size that it warrants two services.

Also 225.39(D) specifies that your disconnect be rated at a minimum of 60 amps, even if you run a circuit of less ampere that that. You must run a ground and neutral that are separate and at the garage panel they must remain isolated from each other. You also must provide a ground rod connected to the panel in that building

Having a neat, properly installed panel and circuits is a wonderful thing. You have few worries about shorts, fires, getting shocked by wires you expected to be cold that are hot, and it makes adding of circuits in the future a snap if you did a little planning. If a panel is installed recessed in a wall, I make wall panels above and below the panelboard that are easily removable by taking out a few screws, then running additional wires to/from the panel is a snap.

You and the person who comes along behind you will appreciate a well planned and executed job.

Charles

 

[pattenp]

I don't know how much you know about this subject. You are getting good info here but you need to understand that you are not getting concise instructions on everything you need to know about putting a subpanel in a detached structure. As mentioned before you need grounding electrodes at the garage, two of them driven 6ft apart. The neutral and ground are not bonded in the subpanel. Separate conductors such as thwn need to be in conduit within the structure. There needs to be a means of a disconnect at the detached structure (and there is an exception to this). The list goes on.

 

[Sterff]

Im kind of leaning towards a 110 compressor now. That sounds like more work and money then I want to get into and still do it right.

 

[pattenp]

My son recently bought a house with a detached garage. The previous owner did the same thing by running two circuits in conduit to the garage. One was 120v and the other was 240v. The big issue was that he use NM cable. I pulled it all out and replaced with proper wire and put in a subpanel. I'm guessing it cost me around $200.