Heater Overloads Keep Tripping During Startup

[Nardie]

So I have a fan motor that keeps tripping the heaters during startup, the starter is a AB 509 starter with a E100 overload relay. The starter and overload relay replaced an outdated set, and worked for a few months. Recently, when we try to start the motor the heaters trip 2-3 seconds. The motor's FLA is 25A, and the overload relay was set to 31A with a 30 second delay. During megger and continuity test between the load side of the starter and motor read good. In addition, we reterminated the motor connections and increased the FLA setting on the overload relay with no difference on the operation. No fuses blown, just the overloads tripping. We did replace the E100 relay with the same result. So what are we missing?

 

[D. Castor]

Have you monitored the actual current during starting? Tripping the OL in 2-3 seconds would indicate a heck of a lot of current.

 

[jim dungar]

Have you followed the manufacturer's instructions for sizing/setting this relay?

 

[Eddie702]

I know you said a fan is the load but is it belt drive? direct drive? Is it a particularly heavy fan to get started?

If the motor gets the fan up to speed, does it trip or is this only a start-up issue?

I agrre that tripping the OL that quick seems odd.

 

[ptonsparky]

Check belt tightness. Too tight has a tendency to wear out bearings leading to overload.

Get your amp meter out. Should have been the 2nd tool out of your bag.