Running a 240v sub panel to garage for car charger

[dsteinhorn]

We moved into a new home with a 200 amp main panel. The garage is detached behind the house about 30 feet and I need to run a 240 v high capacity line to a subpanel. The estimated max load will be total 80 amp serving up to a 50 amp level 2 charger plus shop tools: 220v 3hp is largest equipment and only one machine used at a time).

The total wire run from the main panel to the sub panel in the garage will be 50 ft or less. The feed from main to sub panel will be 3 conductors of 6 AWG THHN plus ground in 1" PVC conduit secured to the fence on the side of the yard. From main panel to beginning of PVC is metal conduit buried 6" under a crushed stone side walkway (about four feet total run). I know the subpanel will require a separate grounding rod to earth because of the separation from the main panel.

My question:
Is the 6 AWG overkill or suitable for this run? Other than having a certified electrician make the connection to the main panel and look over the general installation, do you have other opinions about this project? Is the 80 amp sub panel overkill?

 

[havasu]

I don't know much except when you say it will be buried 6" under a crushed stone side walkway, I believe code is 24".

 

[dsteinhorn]

Metal conduit can be 6" but bare UF or plastic conduit must be 24"

 

[Sparky617]

I'm not sure your statement on the separate ground rod is correct. I believe you keep your ground and neutral bus isolated in the sub panel with the only ground rod being the main ground rod at the service entrance. I'm rusty on the code but I know that is the case when it is all within one building. I'm not positive with it being an outbuilding.

 

[Sparky617]

Metal conduit can be 6" but bare UF or plastic conduit must be 24"

Sounds like the plastic is going to be above ground. He's running metal conduit on the buried part.

 

[dsteinhorn]

I'm not sure your statement on the separate ground rod is correct. I believe you keep your ground and neutral bus isolated in the sub panel with the only ground rod being the main ground rod at the service entrance. I'm rusty on the code but I know that is the case when it is all within one building. I'm not positive with it being an outbuilding.

I know about separating the ground and the neutral bus, because there is the potential for electrical potential differences between ground and neutral at that distance. I will check to see whether I need a separate ground rod outside the garage. I cannot see how it would hurt, though, to have it coupled to the ground at the garage too.

 

[Jeff Handy]

You are running the pvc conduit above ground, attached to a fence?
That sounds illegal.

 

[dsteinhorn]

I’ll check the code. Do you think metal conduit it legal running along the fence?

 

[Jeff Handy]

I have used IMC conduit in situations like that.
Running power to a garage, hot tub, pond, etc, where I did not want to trench and bury everything.

IMC is outdoor rated and has threaded ends and fittings.

Not sure if legal, I usually did not get permits.

Call your local building dept for advice.

 

[bud16415]

I have a 200 amp service and a 100 amp sub in the garage about the same distance you are away. mine is buried the whole run. I don't think a 100 is excessive at all if you could be charging and running one load at a time and maybe a compressor kicks on.

Your wire has to be sized according to full load, distance run, type and size of conduit etc. and then you will get an expected voltage drop. I'm not a pro but you may be small with #6. Pros will be along.

 

[user 4883]

80Amp sub is fine.
yes you'll need a ground rod at the sub
#4AWG between sub & main
absolutely do not attach to a fence, metal or plastic
bury everything to code.

 

[JoeD]

#6 is only good for 60 amps.

 

[afjes_2016]

...Other than having a certified electrician make the connection to the main panel and look over the general installation, do you have other opinions about this project? ...

Other than the suggestions made so far I will give you a heads up on what you said above.

In case you are not aware - if you are planning on doing the grunt work yourself and purchasing the conductors and conduit and then assuming an electrician will be willing to just make the connections at the panels and "look over" the installation I would highly suggest that before you do anything in the way of running conduit, conductors or even buying materials that you first find an electrician that is willing to work with you on this project. You may not be aware of this but many and almost all electricians do not like when a home owner does part of the work whether purchasing materials or laying conduit etc and this is because the electrician does not want to take the liability on their insurance policy. You do not want to get 75% into this project and then find out you can't find an electrician that is willing to finish your work.

It is highly recommended that if you do insist on doing some of the work yourself and buying your own materials that you first find an electrician that is willing to do only the parts of the project that you want them to. You may find yourself in a jam towards the middle if you don't do this first.

I did not let any of my customers do any of the work. I tried a few times but soon realized it was better to let the project go then deal with the problems and take on the liability with my insurance.

 

[dsteinhorn]

80Amp sub is fine.
yes you'll need a ground rod at the sub
#4AWG between sub & main
absolutely do not attach to a fence, metal or plastic
bury everything to code.

Very helpful and also consistent with my thoughts, so I am glad to have them supported by your opinions. I will pull a permit on this and get it inspected by the city inspector.