Motor overload protection

Wheresmywrench?

Wheresmywrench?

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I need to install a new motor protection breaker to my V10-P lathe. I changed the motor from 440V 3 phase to a 240V single phase which draws a little more current 2.2 amps. So what size of a overload breaker should I get? And any suggestions as to what type I should get?
 
Do you turn the motor on with a single-phase/2-pole motor starter which uses thermal overload heaters? If you do you need to get a pair of overload heaters made by the starter manufacturer & refer to their sizing chart. And you should have a fuse or breaker rated at 125% of the motor full-load current or about 2.75 A to protect the motor overload heaters in case of shorts or grounds. Most electrical wholesalers don't stock breakers & mounting kits this size [& it needs to be 2-pole so as to protect both hot leads] so the other alternative is fuses. I'd buy a pair of time delay fuses [Buss FRN-2.8 or equivalent, 3 A will work if you can't get 2.8s] & a matching 2-pole fuse block. I'd go with the same fuses & a 2-pole switch if you don't use a starter although a starter is safer because they can be wired to inhibit motors from automatically restarting when power is restored after being interrupted.
 
No they are not built in they are on separate overloads one for the lathe one for the mill. Main switch activates magnetic contactor then power runs through two separate motor over loads with small dial to set the amperage trip.
 
Ya I think thats what I'm going to do. So how many amps over the 2.2A draw should I go?
 
If you have overloads properly adjusted then your breaker only needs to be for short circuit protection. I don't have a code book with me but I think you can go to 300% of the wire size. Too small of a breaker will nusiance trip on start-up. Circuit size determined by the HP rating and chart from the code book. With that small of a motor I'm sure your circuit will work. Time delay fuses for overload would be at the 150% level.
 
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