Detached Garage Power Plan/MHF

[Hoops.]

I'm about to purchase what I need to run power to my detached garage which is 70 feet from the house. I'm looking for any issues/comments with my plan and answers to a couple questions.
House: Existing 200 Amp service, will add 90 Amp breaker for sub panel.

I plan on using 2-2-2-4 Mobile Home Feeder and I'd also like to run a 14-3 UF wire to operate outside lights on the garage.

Starting at the garage end:
Garage sub panel will be a 100 Amp rated. 2" PVC conduit is run into the garage already through the concrete floor already, so I'll run MHF and the 14-3 UF (in the same conduit)from the sub panel, (into conduit connected to the sub panel), through 2" conduit that will be buried 24" (will be renting a trencher).

Once I get to the house, I'll use Schedule 80 conduit for the exposed section, into a Carlon LB. Once I get to the LB, I'm not sure what I can do. Is it best to switch to SER in the LB? Or do I need a junction box in the basement? What about the 14-3 UF? Can that be switched to Romex in the same LB/junction box? It may just be easiest to run the conduit to the main panel.

Back at the garage I'll be getting two 5/8" x 8' ground rods to be spaced 6' apart. They'll be connected by 6 gauge solid copper wire. Whats a good way to run this wire into the garage? Is it ok to cover the ground rods with concrete after inspection?

Finally, I'm also thinking of running 1-1/4"?? conduit in the same trench, but 12" above the 2", just for future low voltage purpose. I don't have a need today, but I may want RG6 or CAT5 in the future. I may just bury it and cap the ends, or possibly run it into the garage through an exterior conduit/LB. That way 6 gauge solid copper could hide behind that.

If I'm missing anything please let me know...

 

[pattenp]

To switch to SER from the MHF you'll need to use a junction box. The LB conduit body is not large enough. You need at least a 8X8x4 jbox. You could run the conduit all the way to the panel and not have any splices. The UF can be switched to NM, but again it may be easier just to run it to the switch.

 

[alfredeneuman]

The box you will be required to use, if your using 2" conduit, will be at least 12" X (whatever) X 4".

When sizing boxes it's a requirement to size them to a minimum of 6 times the conduit's size in an angle pull (your situation), or 8 times the conduit size if the other conduit leaves the opposite wall of the entrance (straight pull).

It would be a better idea to forget the box, and run the conduit straight to the panel, as pattenp suggested.

 

[pattenp]

This is correct, but when I said at least 8X8X4, I was thinking the #2 conductors are less than the maximum conduit fill for 2", so NEC 314.28(3) would apply for a smaller size box. As I actually read the section again in the 2014 NEC it has become somewhat more complicated to figure the smaller box size so the 6 times rule is the best way to go and not worry trying to downsize the box.

The box you will be required to use, if your using 2" conduit, will be at least 12" X (whatever) X 4".

When sizing boxes it's a requirement to size them to a minimum of 6 times the conduit's size in an angle pull (your situation), or 8 times the conduit size if the other conduit leaves the opposite wall of the entrance (straight pull).

It would be a better idea to forget the box, and run the conduit straight to the panel, as pattenp suggested.

 

[Yarz]

You have almost the exact same plan as I finished doing. Check out the responses I got, when asking similar questions:

http://www.garagejournal.com/forum/showthread.php?t=241016

It may save you from making the same mistake I did.

 

[Hoops.]

Thanks for the helps guys. I think I'll run conduit inside to the panel versus switch to SER. It's only about 15' to run inside. I'll just run the 14-3 in the same conduit to the main panel, but run it right back out to the light switch in the attached garage.

BTW I was talking with an "professional electrician" and he mentioned I could use 14-3 indoor wire if it's installed in conduit versus UF? That surprised me.

With the ground rods, I'm thinking I should get a longer 6 gauge wire and put them in a location where concrete will not ever be versus covering them with concrete in the future.

Now I just need to find a free weekend to rent a trencher and get this project started!

 

[pattenp]

It should surprise you because it's wrong. If the conduit is under ground it's considered a wet location so you need to use UF as you originally planned.

Thanks for the helps guys. I think I'll run conduit inside to the panel versus switch to SER. It's only about 15' to run inside. I'll just run the 14-3 in the same conduit to the main panel, but run it right back out to the light switch in the attached garage.

BTW I was talking with an "professional electrician" and he mentioned I could use 14-3 indoor wire if it's installed in conduit versus UF? That surprised me.

With the ground rods, I'm thinking I should get a longer 6 gauge wire and put them in a location where concrete will not ever be versus covering them with concrete in the future.

Now I just need to find a free weekend to rent a trencher and get this project started!