Overload tripping with no clear reason

[Krohnie]

Hello, working on an issue with a AB 193-1EFDB overload installed on a recirculating glycol system. There are four of these overloads in place and so far two of them have been "commissioned" but continue to trip. Amp draw on the pumps is almost exactly what is stated on the nameplate but we can't get more than 5 seconds of run time before the OL opens up. We're working with 208v single phase pumps, one of the pumps is .75hp and the other is 1hp. Current thought is that this overload shouldn't be used with pumps but I can't find a reason why they would be failing. If we bypass the overload the pumps run with no issue and normal amp draw. Initial load is about 20amps but drops off right away down to 6-7 amps on each motor. Currently the OLs are set to 15 amps with the trip class set to 30.

Thank you

 

[retirede]

If the overload relays are 3 pole, you need to wire them so that motor current flows through all 3 poles. Otherwise they will trip in phase imbalance.

 

[Eddie702]

Are they installed in a high ambient environment?

 

[tom baker]

Class 30 is not a setting I would expect to see for a pump. That has a long trip time, so check application and wiring

 

[retirede]

Class 30 is not a setting I would expect to see for a pump. That has a long trip time, so check application and wiring

Which is another thing that makes me think it’s not wired through all 3 poles. No way a properly wired class 30 should trip in 5 minutes under the given conditions.

 

[jim dungar]

Currently the OLs are set to 15 amps with the trip class set to 30.

Thank you

Some one has not read the manual for these relays, as these are not appropriate settings for the motor data provided.

As pointed out by retirede, all of the relay poles need to see current. Diagrams will be in the manual, but it commonly involves jumpers, like line in at L1 and L3, jumper from T1 to L2 and the motor connected to T2 and T3.

 

[Jraef]

That is an E100 Solid State OL relay but just like the bi-metal versions, if you use it on single phase motors, you must loop back one of the phases so that all 3 poles see current flowing (even though it will be the same current on one of them). If you failed to notice that (on page 20 of the instructions), it will trip on Phase Loss after about 5 seconds.


The basic OL just tells you that it DID trip, not why. If you had installed the Accessory Module or used the Remote Panel Display for it, an LED would have told you why it was tripping, giving you 3 seconds of warning before tripping on a phase loss.