I placed a call this morning to the local inspector, but I figured I would ask my questions here too while I'm waiting to hear back from him.

I need to run wire approx. 230ft from my main panel (which is at the front of the house), to a 60amp main breaker subpanel in my workshop in the back yard. About 50 ft of wire will be inside the house, and the remaining 180 feet will be outside. I know I need to run direct burial wire outside, and I've been looking at aluminum URD for that.

1st question - Can I run the URD wire inside as well? Are their any restrictions to that?

2nd question - I want to make sure that I don't have more than a 3% voltage drop, and I'm unsure what size wire I need to accomplish this. What size aluminum wire would I need to run? I've tried a number of online calculators, but I've been getting varying results.

3rd question - Should I use a conduit, like Liquidtight to protect the wire, or am I safe to just place the wire in the ground?

I'm very new to running wire underground and at long distances, so I appreciate any help. Thanks!

 

Aluminum wire? Why aluminum? I think you should wait for the inspector to return your call.

 

Primarily for the cost savings. I can buy 230ft of 1/0,1/0,1/0 & #2 Notre Dame Underground Secondary Distribution Cable for $400. Copper #3 direct burial would cost double that.

 

I don't remember all of the codes. Wait for Ray or one of the others. They will have the answer.

 

You can run your own calculations http://www.nooutage.com/vdrop.htm. I ran them, and 1/0 aluminum would be overkill based on your needs. You could possibly run #4 copper in PVC conduit, of course not as cheaply, but you would have an easier terminating at each end. With #4 you would experience a less than 1% drop.

Others will have their ideas, so hang in there for possibly better solutions.

 

No. 2 aluminum (#2, #2, #2, #4 the latter for equipment grounding conductor) will do it for you provided the load is reasonably balanced over the two legs of the 120/240 volt line.

 

I would use 2-2-2-4 or 2-2-4-6 aluminum for the outside portion. Burial depth is 24" if directly buried or 18" if you use 1.5" PVC conduit. URD wires cannot run into a building so you will need a splice box on the exterior. Aluminum SER cable is the most likely candidate for the interior portion of the run and Polaris connectors are your best bet for making the transition.

 

Couldn't he just use mobile home rated cable and use the same cable both inside and buried? That would certainly be easier than splicing.

 

Yes he could, but the MHF (mobile home feeder) needs to be in a fully assembled conduit through a building. It is an option, but not as easy to install compared to SER which can be stapled directly to joists.