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Discussion Starter · #1 ·
Seeking some advice on installing a sub panel in a detached garage. I have a 200amp main in my house and I plan on installing a 90 amp sub-panel in a detached garage approx. 100FT away from the main panel.

In order to avoid having to run a conduit in the house, I am planning on running 2-2-2-4 SER Aluminum cable from the main panel through a crawlspace into a metal junction box, then transition over to MHF. The MHF wire will run from that junction box through a rigid conduit buried 6” underground directly into the garage panel. Using Rigid over PVC due to the rocky soil making it difficult to dig 18” deep. I plan on installing a grounding rod next the garage which will ground the sub panel. Can I run the wire in this manner or does the rigid conduit need to be bonded back to the main panel?

Would I be better off running MHF the entire way and running it through EMT within the house from the main and transitioning to the Rigid conduit for the underground? Any advice would be greatly appreciated. Thanks.
 

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Personally I would run conduit whenever I could.
Have you priced out the cable vs individual wires in conduit?
Conduit always provides a neater installation.
You can bury the metal in the rocky soil and transition to PVC since you will be running a ground wire anyway.
I would think at the very worst the cost may be the same.
 

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Discussion Starter · #7 ·
Personally I would run conduit whenever I could.
Have you priced out the cable vs individual wires in conduit?
Conduit always provides a neater installation.
You can bury the metal in the rocky soil and transition to PVC since you will be running a ground wire anyway.
I would think at the very worst the cost may be the same.
I haven't priced it yet, but I am also assuming the cost will be similar. The advantage of separate wires makes it an easier pull, but the conduit is 2" and a straight run with just 2 bends so hopefully it shouldn't be too difficult. Appreciate the advice, something to think about.
 

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Conduit is the way to go. PVC is the most cost effective. 2-2-2-4 Al. would work with 90amp breaker. Will need to establish grounding at seperate building.
 

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I thought so.
Too bad you didn't ask your question before you bought everything.
We may have been able to save you some $$$$
 

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first no ground at garage.U will have to run 4 wires ground included. 90 amp????
The panel will need a grounding system . The panel does not meet the exception for a single circuit.
 

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Sounds similar to my garage service. The distance was just over 100 feet. I ran the mobile home feeder the entire distance in 2" PVC. There were 6 90's, two of which were pull boxes. No trouble pulling cable.
Check with your locals, some require 2 grounding rods.
 

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Mine is similar except 100 amp outbuilding. At the time (1995) I had the option of running a 4th wire for ground or a ground rod at the sub panel. The theory was that it could not be grounded at both ends and interconnected. Ground potential is different from place to place. If two grounds are different and connected, they would try to balance out making the ground conductor a current carrying conductor. That was not permitted. It was one ground, sometimes being 2 ground rods in close proximity.
 
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