Higher size starter lowr size Motor

[SilverArc]

Hi,
This is my first question on Motor forum.

I was wondering, can I use a 60 HP fan motor on a size 5 NEMA starter which is good between 100-200 HP motors.

Actually, the client does not want to buy a new starter and wants to use same starter when he is done with 60 HP fan application, he will replace it with 125 HP.

I spoke to Allen Bradely and their tech support advised me that you can do that but you will have to have a new overload for 60 HP fan(size 4 starter overload) and replace with size 5 starter overload.

Could you kindly advise, if any one of you have ever come across issues like that.

Thanks

 

[waross]

It depends on the design of the overload relay. In some designs you are able to change heaters in the overload relay. Overload heaters are low cost items.
In other designs the heaters are not changeable and the entire overload relay must be changed. This is more expensive.
Be sure to use the proper sizing chart for overload heaters.
A 60 Hp. motor may not use the same heaters in a size 4 starter as it will in a size 5 starter. This is an issue with some other manufacturers but I am not sure about Allen bradley specifically.
respectfully

 

[jraef]

Also if you have a circuit breaker or fuses associated with that Size 5 starter they will not be appropriate for a 60HP motor.

 

[SilverArc]

if we use an Motor Cicruit Protector, do you think we still might have an issue with that ?
I beleive in a MCP, you can just change the settings on the dial.

Other option possible could be, Change the fuse and overload as required and we are fine ?

Thanks

 

[dpc]

Even with an MCP, the adjustment range for the instantaneous trip is limited. The MCP must be matched to the motor horsepower, as must the overload relay.

The contactor can be used, but short circuit and overload protection will have to be changed out to match the motor FLA.

 

[jraef]

60HP 460V should be around 77 FLA x 13 = 1001A. This is the highest possible setting you could use on that MCP. If your MCP adjustment does not go down to 1000A, then you can't use it. It should though.