TwinCitySparky
Senior Member
- Location
- Minnesota
I have a heat trace -roof application- question. Manufacturers info shows me that my 170' long cable is to be protected with 30A @ 120 volts. The cable consumes a fairly large inrush current at start-up. The application was pre-wired with a dedicated circuit, 12G THWN wire, 20 amp breaker and 20A GFCI.
Per instructions if cable length was 130' I would be fine with 20 amp capacity. But the extra 40' of cable pushes me into the 30A category. So I tentatively approach my NEC book...
The vast portion of the circuit is ran in PVC conduit outside where ambient temp will always be below freezing. (Wintertime) 5' of the circuit is ran inside the heated garage which is kept at about 55 Fahrenheit.
Using the 90C table for THWN (obviously far below my app. temp) I think I'm OK using a 30 breaker with my 12G wire. Am I compliant or confused.
Per instructions if cable length was 130' I would be fine with 20 amp capacity. But the extra 40' of cable pushes me into the 30A category. So I tentatively approach my NEC book...
The vast portion of the circuit is ran in PVC conduit outside where ambient temp will always be below freezing. (Wintertime) 5' of the circuit is ran inside the heated garage which is kept at about 55 Fahrenheit.
Using the 90C table for THWN (obviously far below my app. temp) I think I'm OK using a 30 breaker with my 12G wire. Am I compliant or confused.