Reply by CaptainKlutz

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Posted on Baileigh JP-1686 Three Phase Electrical Question

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5170 posts in 2836 days

#1 posted 10-20-2021 06:35 AM

Hmm, lots of missing details, too many to offer recommendation.
But here are some factors to consider:

- 3 phase power CABLES including a neutral have current de-rating due number of ‘hot’ wires in bundle. So the AWG of wire needed in your hookup depends on wire/cable type.

- Max current carrying capacity on wires depends on temperature rating of the connections. There are also ambient de-rating factors to consider if your wiring location will exceed 30°C. NEC requires the use of lower 60°C table rating on commonly used residential NM jacketed cable, so your wire type and location can also change the required size.
There are many online wire current carrying tables, but this one has nice summary of the de-rating factors on page 2.

- RPC feed wiring should be sized according to the mfg recommendation, and then adjusted for local de-rating factors on distance and/or wiring type. What is size/brand/model of RPC motor?

- The start up surge is often quoted as 2X FLC, which is 28A for 5HP 230v 1PH motor. The 60A service mentioned above would be quasi-standard (worst case) circuit for industrial 5HP motor installation, though a modern 5HP 1PH motor runs on 40-50A circuit.
For a 60A 240v feed line, I would likely use #6AWG copper wire minimum or maybe #4AWG aluminum. #8AWG mentioned above is only rated for 40A at 60°C or 50A @ 75°C.

- While you are doubling current of the feed circuit, be sure to calculate and verify max load values for the panel and supply line.

When in doubt, hire a professional electrician for upgrade work.

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