I was asked today about the requirements for powering a 1500W 120V livestock water tank de-icer that was 500-600ft away from the panel. First thought that came to mind was "sub-panel". At that distance is it even reasonable to run conductors straight to the heater? At 500' and using a 3% voltage drop I ended up with #4 Cu (75 degree Celcius column Table 2 CEC). Wouldn't a small sub-panel placed closer to the tank and then running smaller gauge conductors to the heater be a better idea?
