dpwell
Member
We're preparing to install the electrical run to a 5 HP 230 VAC 3 phase submersible pump motor. The total length is 440'. It will start at a 60 AMP fusible disconnect with 40 AMP dual element fuses. The conductor size will be #6 for 200' to the combination starter pump motor control panel. We will install 20 AMP dual element fuses in this panel and from there the conductor size will be 240' of #10 cable to the pump. The minimum wire size for the motor is #14 good for only 140' with a 5% maximum recommended voltage drop, according to the motor manufacturer (the minimum cable size we use for submersible motors is #12). The motor conductor size has been increased to keep voltage drop below 5%. The electrical system at this facility is old and distribution is from a fusible disconnect to a gutter with multiple fusible disconnects. Generally on a more modern system, without the extended run, we would install a 40 AMP circuit breaker followed with #8 conductors and a #10 ground to the pump panel. From the panel we would go with #12 cable down to the motor (the ground conductor on submersible pump cable is the same size as the other conductors up to #10). A county inspection may be required for the electrical installation. I would like the ground wire to be sized correctly regardless. What I'm not sure about is increasing the ground wire size in proportion to the motor conductors size, which has been increased to compensate for voltage drop. It's the #6 run that's in question. Do I start with the #8/#10 combination and go to a #6/#8 combination or do I go back to #14/#14 combination and use a #6 for the equipment ground?
