Fused disconnect as motor overload

[Sparky1212]

Is there any problem with using a fused disconnect, then an inverse time breaker for short circuit protection? Looking through the code book I didn't see a problem with it. Just wanted to hear some other inputs on it. Hooking up a 240v 50 amp 10 hp motor.

 

[Dennis Alwon]

There is no problem using a fused disconnect but your heading is talking about overload so I am confused. If there are no overloads built in the motor then you have to supply overload protection and that can't be done with fuses

 

[tom baker]

The overloads protect the motor, the breaker protect the wire.
For motor branch circuit, short circuit and ground fault protection, Part IV of article 430, I prefer time delay dual element fuses, as they can be sized much closer the motor running amperage. A typical TM circuit breaker has to be sized much larger to allow the motor to start and come up to speed.
However, many electricians don't like to use fuses as it requires keeping spare fuses.
Bussman has some interesting literature showing how a TM or IT breaker will allow motor damage.

And what it comes down to is what is the cost of the motor, a small 2 hp motor is not worth rewinding, so a TM breaker may be the best way to go

Your topic title is fused disconnect as motor overload, typically OL protection is done in the motor starter.

 

[augie47]

I rarely see it done. On 3 phase motors using fuses fir OL it seems there is a greater probably of single phasing and loosing the motor and maintenance folks are notorious for oversizng the fuses.

 

[Dennis Alwon]

I realize fuses can be used for overload as Gus pointed out to me but the probability of a fuse being available for the overload size is not likely-- I think so anyway...LOL