ITgeek
Member
- Location
- Northern Michigan
Here is the situation: I have discovered (in my recently purchased home), the electrician ran ONE 12/2 UF cable from the main panel to the 2nd garage's subpanel. I estimate it's a 450 foot run. The cable was run in 1 inch poly irrigation pipe. I'm pretty sure it's not HDPE conduit as I saw no markings on the section I unearthed. The voltage drop calculators say I need to run 6 awg cable to get 20 amps at the subpanel with 3% voltage drop. Is it a code violation to run URD cable through that pipe?
Single conductor 6 awg URD cable is more expensive than 4-4-4-4 URD quadraplex cable, however it doesn't look like Appendix C in the 2017 NEC lists fill capacity for direct bury wire. Since URD likely has thicker insulation than THWN or XHHW I don't think I would be allowed 4 conductors at 4 awg, My assumptions are compact conductor wire will be used and the 1 inch poly pipe has equivalent diameter to 1 inch HDPE conduit.
The reason I'm going through this exercise... For new conduit I have to run it down my compacted gravel driveway, over my buried utility line, the buried 7200 volt service to the transformer that services my house and my neighbor, 3 drain culverts, underground natural gas service 2 or 3 times, and under a private dirt road to my garage.
I did check with my local electric co about running service to the garage. Their fees seemed reasonable but I'll pay $20 month for the 2nd meter. I have a whole house generator so I'd keep the current subpanel for lights and the garage door opener.
Single conductor 6 awg URD cable is more expensive than 4-4-4-4 URD quadraplex cable, however it doesn't look like Appendix C in the 2017 NEC lists fill capacity for direct bury wire. Since URD likely has thicker insulation than THWN or XHHW I don't think I would be allowed 4 conductors at 4 awg, My assumptions are compact conductor wire will be used and the 1 inch poly pipe has equivalent diameter to 1 inch HDPE conduit.
The reason I'm going through this exercise... For new conduit I have to run it down my compacted gravel driveway, over my buried utility line, the buried 7200 volt service to the transformer that services my house and my neighbor, 3 drain culverts, underground natural gas service 2 or 3 times, and under a private dirt road to my garage.
I did check with my local electric co about running service to the garage. Their fees seemed reasonable but I'll pay $20 month for the 2nd meter. I have a whole house generator so I'd keep the current subpanel for lights and the garage door opener.
