Underground wiring from garage to shed depth

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  #1  
Old 03-13-16, 07:59 PM
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Underground wiring from garage to shed depth

I will be running power from the garage to shed. It is a separate circuit in the garage that will be used in the shed. I will use a gfci for that new circuit before it goes in the ground.

My local codes just go by the national codes and that's it.

I read somewhere else that if I use galvanized rigid conduit with watertight fittings it only has to be 6" below the surface?
Is that correct or will it have to be deeper? If possible I would like to dig less even though it might cost more for the conduit.

If I can do the Galvanized rigid conduit what wire could I use then for a 120v 20a circuit. 30-50 foot run from garage to shed depending where I come in from.

Thanks
 
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Old 03-13-16, 10:05 PM
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#12 THWN. PVC is easier to work with and can be buried at one foot if GFCI protected and 20 amps or less. RMC/IMC is six inches with or without GFCI protection so you could just use a GFCI receptacle in the shed. Depending on breaker cost you might save a bit.
 
  #3  
Old 03-14-16, 04:19 PM
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Thanks,
I am now starting to think about the future and trying to see what my options are.
The biggest challenge is in the path, is tree roots from a 2' diameter tree that is approximately 10 feet away from the path line from garage to shed. I am trying nut to cut big roots.
I dug 6+ inches already but not sure if I want to try for the 18" for future options with PVC.

I will be using only this one circuit in the first post right now but wanted to see if I added a couple more lines in the future what else would be needed.

One 220V line for a air compressor single stage 20a guesstimate
and another line for house backup generator 5000 Watt (6500 peak) I believe
So 3 circuits total including the first one in the first post.

Can those 3 circuits be ran in the same galvanized rigid pipe at a 6" depth? I would probably go with 2" pipe as that's all my local Lowe's has in stock except for a couple 3/4"

If I did dig the 18" and used the PVC does the same answer apply with running all 3 circuits in the same pipe at 18"?.

It is in my back yard so no driveway road etc, just grass.

Thanks for your help.
 
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Old 03-14-16, 05:20 PM
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Can those 3 circuits be ran in the same galvanized rigid pipe at a 6" depth? I would probably go with 2" pipe as that's all my local Lowe's has in stock except for a couple 3/4"
No. Code prohibits more than one circuit. You will need to install a subpanel at the shed for your 120v and 240v (not 220) loads. This will require a 4 wire feed. Probably either three #8 and a #10 or three #6 and a #10 depending on your loads.

The generator is a totally different problem. I doubt you can wire it in through the shed without a lot of extra work. It must be connected to your main electrical panel using, a transfer panel or transfer switch or an interlock. The interlock is the least desirable and may not be allowed by local code.
 

Last edited by Tolyn Ironhand; 03-15-16 at 06:18 PM.
  #5  
Old 03-15-16, 07:41 AM
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The interlock is the least desirable
If using a portable generator I believe it's the most desirable because it gives you the full flexibility to pick any circuit to be powered when needed. With a transfer switch you need to determine upfront which circuits will be connected to the transfer switch.
 
  #6  
Old 03-16-16, 09:54 AM
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The generator I will hold off on right now.

Question on fittings on using RMC underground. I am getting conflicting answers probably I don't know the trade terminology but..

Can the 3 piece couplings be used underground? Some say no some say yes.
I see a lot of 3 piece couplings are Threaded when searching online but Lowes has this Shop Gampak 3/4-in Rigid Coupling at Lowes.com would this work if the threads are cut off? Or is that for a different pipe? Looks like it is compression, not threaded and is zinc plated.
Does it have to be galvanized or is zinc OK?

Thanks again for everything.
 
  #7  
Old 03-16-16, 12:45 PM
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If using a portable generator I believe it's [interlock] the most desirable
Many of the ones sold are not approved by UL or similar agency. National code says unapproved devices can't be used. Many can easily be defeated by removing the cover. Local code sometimes prohibit their use.
 
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Old 03-16-16, 02:53 PM
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Many of the ones sold are not approved by UL or similar agency.
Where are you getting your information from that many of the interlocks sold are not approved? Can you name a few? Major manufactures of panels such as Eaton, Schneider and Siemens make interlocks for their panels; are those not approved?
 
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Old 03-16-16, 05:42 PM
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Yes, those are approved but they are expensive so a lot available are cheapies with no approval. My conclusion is based on what has previously been posted here. Perhaps the pros can better address your questions.
 
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