Help with 220v to shed?

[TheGreek]

Hey guys. I'm hoping to get some ideas, suggestions and feedback for my next project. Have a read and post some thoughts.

I am going to be installing a 100 amp subpanel in my attached garage off my 200 amp service. I have about 12 to 14 spots available in my current panel. I will be running #2 aluminum SER less than 100 feet to my garage. I will be powering a 220v Bendpak lift, a 220v welder and 220v plasma cutter as well as a few 110v receptacles. From that subpanel I will be running power out to my storage shed.
I will have a few outlets for some power tools, a light inside the shed as well as a flood light on the outside. I will also be housing my 5hp 80 gallon craftsman compressor in the shed. Its currently a 3 phase but I will be converting it to 220v single phase. I will be running 2 pvc pipes underground in a trench 18 inches below grade. One for my electric and one for my air lines. I will be running #6 thhn out to the shed through the conduit. I havent done any calculations to determine the size of the pvc pipe but I will be going larger than necessary if possible. It is my understanding that any outdoor receptacle must be GFI. Does this apply to receptacles inside a shed as well? How would this apply to the 220v power? Does it make a difference if the compressor is hardwired or uses a plug? I haven't heard of anyone running 220v to a shed before so if anyone has ideas id love to hear them. The inspector wasn't available when I went to ask about my permits so I need to put together a quick schematic to get all my permits filed.
Thanks in advance.

 

[Charles (in GA)]

Using ENT (Electrical Non-Metalic Tubing, ie. PVC conduit) and THHN wire, you need one inch to carry more than three #6 THHN wires (1" will handle up to 6ea #6 THHN according to Table C2 of the NEC).

Grade level/ ground floor in accessory structures require GFCI on 120V receptacles.

Charles

 

[Norcal]

If on the 2008 NEC 1/0 AL SER cable will need to be used for 100A, NM & SER cable must be sized in the 60 degree column in table 310.16.

 

[mrb]

Using ENT (Electrical Non-Metalic Tubing, ie. PVC conduit) and THHN wire, you need one inch to carry more than three #6 THHN wires (1" will handle up to 6ea #6 THHN according to Table C2 of the NEC).

Grade level/ ground floor in accessory structures require GFCI on 120V receptacles.

Charles

ENT is the corrugated stuff, commonly referred to as smurf tube when its blue

RNC would be pvc conduit.

 

[TheGreek]

Ok I'll have to check what I wrote down for the aluminum ser wire in my records. I may have confused my copper and aluminum sizing. Thanks for pointing that out.

 

[Charles (in GA)]

ENT is the corrugated stuff, commonly referred to as smurf tube when its blue

RNC would be pvc conduit.

Well, I should know better, been a long day at work and thats my story and I'm sticking to it. Sch 40 PVC is 3/4 min for 4 #6 THHN and Sch 80 is 1" for the same.

Charles

 

[TheGreek]

Thanks Charles
I've come across a few sites where people have used a separate panel I'n the shed. Would that be the only way?

 

[mdale]

What would be required if you were only running 120v to a shed?

 

[TheGreek]

From the info I have gathered, you would need to run a line off a panel through an underground conduit. As far as I know you would need to install GFI receptacles. I havent gotten my permits yet so I haven't submitted any drawings.

 

[mrb]

Ok I'll have to check what I wrote down for the aluminum ser wire in my records. I may have confused my copper and aluminum sizing. Thanks for pointing that out.

SER cant go in the ground.... you need something listed for wet location

 

[TheGreek]

The SER will be in the basement from main panel to subpanel in the attached garage. The THHN will go in conduit from garage to outdoor shed. That should meet code right?

All the electricians that came to give me quotes said they would be using #2 SER cable. Not sure what the inspector will require in my town so I am waiting for them to get back to me.

 

[bjcouche]

Since you are staying above ground and in dry locations between your house breaker box and your garage sub panel, you can use SER cable. Keep in mind though that you need 4 conductor, 2 hots, a neutral and a ground. Some SER cable is for services and doesn't have the ground wire... The ground bar in the subpanel should be isolated from the neutral. I won't get into the argument as to whether 2awg aluminum is good for 90 or 100A but beware, it may depend on the inspector or who you ask.
As to the shed underground feed, I'd place a small subpanel in there as well. I can't think of any other way to do it if you plan to have a 240V compressor and 120V outlets. A small 60A subpanel is fairly cheap at your big box stores. Remember to get one with a main breaker to be used as a "disconnect" Don't worry if the main breaker is 60A but the breaker you are feeding it from the garage is smaller as the one in the shed is only being used as a "disconnect" and not overload protection.
You didn't mention how far the shed was from the garage. Since you are placing it underground, even if it's in conduit it has to be rated for wet locations. You might want to compare the price of your suggested THWN copper wire 6awg I think you were thinking of, to aluminum. You might find that you can use USE/RHW 2-2-2-4 "mobile home feeder" and it may be cheaper than the copper and give you more power with less voltage drop... There is nothing saying you can't use larger wire rated for 90A but only put it on a 60A breaker. The only catch is to verify that the breaker supports that size of wire in it's terminals. You might even be able to forgo the conduit because it's direct burial, but I'd use the conduit anyhow. Don't fear the aluminum, just use it properly, Copper is soooo expensive now.

Brian

 

[Norcal]

Since you are staying above ground and in dry locations between your house breaker box and your garage sub panel, you can use SER cable. Keep in mind though that you need 4 conductor, 2 hots, a neutral and a ground. Some SER cable is for services and doesn't have the ground wire... The ground bar in the subpanel should be isolated from the neutral. I won't get into the argument as to whether 2awg aluminum is good for 90 or 100A but beware, it may depend on the inspector or who you ask.
As to the shed underground feed, I'd place a small subpanel in there as well. I can't think of any other way to do it if you plan to have a 240V compressor and 120V outlets. A small 60A subpanel is fairly cheap at your big box stores. Remember to get one with a main breaker to be used as a "disconnect" Don't worry if the main breaker is 60A but the breaker you are feeding it from the garage is smaller as the one in the shed is only being used as a "disconnect" and not overload protection.
You didn't mention how far the shed was from the garage. Since you are placing it underground, even if it's in conduit it has to be rated for wet locations. You might want to compare the price of your suggested THWN copper wire 6awg I think you were thinking of, to aluminum. You might find that you can use USE/RHW 2-2-2-4 "mobile home feeder" and it may be cheaper than the copper and give you more power with less voltage drop... There is nothing saying you can't use larger wire rated for 90A but only put it on a 60A breaker. The only catch is to verify that the breaker supports that size of wire in it's terminals. You might even be able to forgo the conduit because it's direct burial, but I'd use the conduit anyhow. Don't fear the aluminum, just use it properly, Copper is soooo expensive now.

Brian

If the OP area's has adopted the 2008 NEC, 1/0 AL is what is required for 100A, a rule change occured that now requires SER cable to be sized from the 60 degree column.

Upsizing wire is a problem because of NEC art. 250.122 requiring the grounding conductor to be up sized proportionally when the ungrounded (hots) are upsized.

SE is 2 insulated conductors wrapped w/ a bare neutral conductor, SER has 3 insulated conductors w/ a bare grounding conductor.

 

[TheGreek]

Thanks for the feedback guys. This is exactly what I was hoping to hear. Lots of good info. Some I have heard before some I haven't. The shed is about 75 feet from the house. Add about 15 feet to that for wiring and it's just under 100 feet. I'm still waiting to hear from the electrical inspector to hear his recommendations on the wire sizes and types as well as what he wants me to do for the 220v. Would hardwiring a piece of equipment make it easier and get rid of the need for the panel in the shed? Since outside receptacles must be GFI what else could be done?

I was also wondering about expansion joints for the PVC conduit. What is the requirement?

 

[Aceman]

Who is doing this job?

You or the electricians?

 

[TheGreek]

I am planning on doing it. Estimates I got for the job were very high and I am more than capable. Gotta learn sometime.

 

[mrb]

I am planning on doing it. Estimates I got for the job were very high and I am more than capable. Gotta learn sometime.

I suggest before beginning work or buying anything, start a new thread with what you plan to do. Then weed out the incorrect advice (usually about grounding, mwbc, or wire size and type). We have saved several first timers ALOT of trouble, and a few have realized they had major work to redo after they posted their completed project before running it by us first.

 

[TheGreek]

Sounds good. My permits are ready to be picked up so I will talk to the inspector and when I'm ready I'll start a new thread. Thanks guys.

 

[mrb]

Sounds good. My permits are ready to be picked up so I will talk to the inspector and when I'm ready I'll start a new thread. Thanks guys.

remember, its not the inspector's job to design your installation and they often miss things.

 

[TheGreek]

At this point the inspector had a stroke and is on limited duty so I can't even get in touch with him to talk and see what he has to say about my proposal.
The shed is up and I'm in the process of digging my trench. There is so much construction debris so it's taking me much longer than I thought. I'm hoping to have to have the trench dug and PVC pipe layed in it and inspected next week. After that I'll start with the wiring. I decided to go with a separate subpanel In the shed to make my life easier. I'll be running two separate 1-1/2 inch gray PVC in my trench. 1 for my 4 conductors and the other for an airline and anything else. I'll go through both the walls of the house and the shed with 90 deg pull throughs. Want to get the tubing laid down before the hot weather.

 

[TheGreek]

Trench has been dug and PVC is laid in place. Waiting for the trench inspection.