What type and size conductors and conduit should I use to feed a detached workshop

wire

I'm planning to install a 100 amp sub panel in a new detached workshop in my backyard. I will run power from my home main 200 amp service panel which I have a dedicated 120/240v double pole 100 amp breaker already set up. Consumers in my workshop will be

  • 6X linear fluorescent T5 light fixtures 11 amps
  • 2x exterior wall pack lights 10 amps
  • Garage door opener 15 amps
  • AC/DC stick welding 50 amps
  • Air comp. 20 amps
  • Table saw 15 amps
  • Shop fan 15 amps
  • Bench grinder 15 amps
  • misc small AC power tools.

I anticipate approx 55-65 amps will be the most continuous current at any given time. The cable run distance from the 200 amp main service panel to the sub panel is 185ft. 110ft will be under ground and 75ft will be run inside my home through the attic. I would like to make this pull all in one with no splices.

My questions are

  1. What type and size wire is suitable and meets Electric Metro code to run inside my home and also bury 24" in conduit?

  2. What size and type conduit (PVC or galvanize) should I used for under ground and what is the NEC code for conduit above and below ground.

Best Answer

I don't know what the "Electro Metro" code is, nor do you mention your location, so keep in mind my answers are based on a US installation under the NEC.

PVC conduit is fine for the whole run, and the easiest BY FAR. You can use Schedule 40 for any and all parts, buried or exposed but not subject to damage. Areas like where it emerges from the ground outside you'd need to use Sch80. Again, 18" deep (to the top of the pipe) is fine for any residential installations. Table 300.5 is the NEC section for this.

Personally I'd go with #2AL for cost savings and 1-1/4" pipe. Since you'll have a mix of 120V and 240V loads you can run one #2, one #3 or 4 neutral, and a #6 ground. They do sell 100A MHF (mobile home feeder) cable that has this combination already grouped together. Remember, this type of wire/cable cannot be run exposed. You'd have to run the conduit completely from point to point. You could also run the conduit to a big box in the house then change over to #2SER cable, but this takes some skill and knowledge to make the change over and splice.

I'd put this on an 80 or 90A feeder breaker in the main panel.

Related Topic