There is a 480V 3phase heater, 63kw, 74 amp heater installed in the facility. It was sized at 125% it looks like due to heaters being considered continuous load. 74A x 1.25= 92.5A. They ran 3awg thhn which is rated at 100A at 75C terminations. There is a 100A fused disconnect beside the heater with 100A RK5 dual element fuses. I traced the 3awg back to a motor control center 200A fused switch that was fused at 200A. This application does not fall under any of the tap rules since it is a straight run. Does the 100A fuses in the heater disconnect even need to be there and could just be installed at the MCC fused switch? That would allow those to be used for the branch circuit OCPD and the heater OCPD? I just don't like the idea of having 100A fuses in the heater disconnect running back to another set of fuses at the MCC at 200A rk5 fuses.
Feeder Protection?
- Thread starter User2
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
The conductors between the MCC and the disconnect are as you've stated tap conductors therefore the tap rules would apply. You could just change the 200 amp fuses to 100 amps and eliminate the tap rules from the equation.
- Status