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Thu 23 Oct, 2014 11:41 am
I built a 12x18 studio and now want to feed the supply for [2] 6' electric baseboard heaters wired on 1 thermostat [1500 watts, ~ 6 amps draw each] and 2 circuits for lights, stereo system , etc. I figure they will be on [2] 15 amp breakers.
The studio is about 175' from the main house. The main house has a 200 amp service and panel. Plenty of space in the box.
What gauge service wire can I get by with to supply the above? Would 10-3 work?
I would run it in conduit 18" below ground.
I need only enough room in the new studio box for a main breaker, a double breaker [probably 30 amp?] for the heaters, and [2] 15 amps for the duplex/lights. But I can only find a small 100 amp box that will allow me the required space. Do I have to use 100 amp service wire to feed that?
Thanks for any help.
@phillyshriv,
The two heaters can operate on a 20/2 breaker. The heater load is figured at 1.25%. The two 15 amp 120v circuits I figured the max of 12 amps kper circuit. The total load would be 27.62amps. At 175ft I would run #8 conductors with a #10 ground conductor. You could use a 30/2 at the service panel and backfeed at 30/2 in a panel at the studio as long as a hold-down clip is on the breaker. The voltage drop at full load with #10's would be 5.07% and with #8's would be 3.19%. If you use the larger wire you have some room should you add something in the future. I doubt you would see full load on the 15amp circuits so the VD would probably be less than the 5.07% in actuality. You will need a ground rod and disconnect (the 30/2 backfeed can be used). The neutral
should not be bonded to the grounding conductor at the studio but a spearate ground bar should be in installed in the panel for connection of the circuit ground wires. You can buy the 100amp panel and feed it with the 30 amp circuit.
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