We have a homemade hydraulic press. It has a 5 hp 3-phase electric motor that currently is turned on by plugging it into a wall outlet. I want to put in a switch to prevent the uneven motor start up, being able to shut it off immediately, and to prevent the arcing when it is being plugged in. I bought a 3hp rated safety paddle switch, like what would be used on a table saw before I knew the hp rating of the motor. I would replace it with a similar higher rated switch, but I cannot find one with the safety paddle. My dad thinks the 3hp switch would work, pointing out that the press is used probably less than an hour in a month.

I would need more power cord to mount the switch where I want it. The current plug uses 8/4 cord marked “SO.” The local big box store has 10/4 marked “SJOOW.” I was thinking about rewiring the whole thing with 10/4 cord but not sure if it can handle the load. The total length from outlet to motor would be under 25’.

This is beyond my comprehension of electrical wiring, so any suggestions are appreciated.

 

The 10ga and wire and the switch will probably work fine for what your using it for.

 

This is beyond my comprehension of electrical wiring, so any suggestions are appreciated.

Hire a qualified electrician to do the installation, you may need a motor starter control circuit, for the on/off operations depending on inrush currents of applied pressures and frequency of stop start cycles during your pressing tasks, arching by plugging and unplugging indicates load making and breaking not its intended purpose to plug and unplug. The sizing of the conductor is dictated by the National Electric Code. Suggestion hire a trained professional.