Wiring A 60 Amp Breaker Box In A Detached Garage. Apr 28, 2011I am going to wire a 60 amp breaker box in a detached garage. I will wire it underground from the house box. The length of the wire will be 100 feet. What size wire should I use? Do I use 2 wire with ground or 3 wire with ground? Currently have 8 gauge coming from house to garage with small 4 fuse box.Hi, I'll be glad to assist you. 2 #6 THHN copper and 2 #8 THHN copper. You will also need to drive a ground rod and use a #6 copper ground wire.I assumed and would strongly advise that you put the feeder in PVC pipe. The #6's are the hots and the #8's are the neutral and the ground.One little roch penatrates the insulation and there is a failure. You would have to dig it up to replace or repair. Pipe is insurance that it won.. In my pool house I have a 60 amp fuse box with 4 15 amp Apr 09, 2014In my pool house I have a 60 amp fuse box with 4 15 amp fuses. In one of the circuits there is an electrical outlet with a portable hot tub plugged in drawing 15 amps. It has run fine for a year. This past weekend a bunch of young people were playing ping pong in the pool house and decided to plug a portable oil heater into the same circuit.