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Paul, Lets start with: My Uglys Electrical Reference shows a Single Phase 5 HP AC Motor draws 28 amps full load current at 230 volts, which would be a lil less at 240 volts (23 to 25 or so???). Next, theres not one but two things that need to be protected. ONE the Motor needs thermal overload protection so the motor doesnt overheat and damage the windings TWO the branch circuit feed wires need protected from exceeding their ampacity so as not to degrade the insulation. Nowwwww the motors thermal overload protection may be built in (like the lil red button that pops out on overload) orrrrr rr one utilizes a "Motor Starter" which has devices called heaters that sense overload conditions and open the relay controlling the motor. Sooooo ooooo Im gonna assume the motor has a built in thermal protection device or you already have a starter and alllll l we gotta do is provide a branch circuit and protect the feeders buttttt ttt still allow the motor to start (draws like 6 x current momentarily while starting). without tripping a circuit breaker if you feed it with such orrrrr rrrrr r if you feed it with a fuzed safety switch, get it fuzed to protect the feeders n still allow the motor to start. CIRCUIT BREAKER Ok the NEC changes n Im rusty having been retired a longgggg gg time n Im too lazy to look it up lol but heres how we used to do it..... If the motors full load current is NO MORE THEN say 24 amps, thats 80% of a 30 amp circuit breaker and theoretically you could use a 30 amp breaker and 10 gauge wire BUTTTTT TTT unless that 30 amp breaker is one specifically designed for motor starting, a 30 amp MAY WELL NOT let her start buttttt ttttt a 40 amp breaker probably will. ALSO since the 10 gauge wire is sooooo oo close to the allowable limit and especially if its a long run, I believe as a matter of practice I would use 8 gauge feeder wires. Those wires and a 40 amp breaker should allow her to start,,,,, ,the feeders are protected,,,,, the motors thermal overload will protect the motor Yayyyyy yyyyy y FUZED SAFETY SWITCH if you use a blade type Safety Switch to serve the motor, this is an easier call, you can use a 30 amp dual element time delay (motor starting) fuze cuz it willlll ll allow momentary overcurrent to allow the motor to start but then operate as a 30 amp protective device otherwise and assuming youre at 24 amps max current, youre within the 80 % of 30 amps. But again, if its a long run to reduce voltage drop, Id likely use 8 gauge wire. Then there are the NEC motor rules about a disconenct having to be within sight and not more then 50 feet away subject to some exceptions like lockable safety switches buttttt ttt as a matter of good prctice and safety and for no more then they cost, I would use a blade type safety switch (it dont need to be a fuzed swith if the feeders are already protected back at the panel) near the motor with seal tight flexible (NEC reduces vibration transmission) conduit ran from it to the motor, NEMA 3R Enclosure if outdoors or NEMA 1 if indoors. Hope this helps, stay safe, Best Wishes n God Bless John T Longgggg retired n rusty Electrical Engineer
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