Motor control contactor

[gregorymcadam]

I have been working on a control panel for a chiller fan motor . The controller has a "hand-off-auto" switch . When the switch is on the "hand" position everything runs normal . When in the "auto" position after awhile of running the breaker trips .
Any ideas to this issue

 

[ptonsparky]

You didn’t run the motor in hand as long as it ran in auto.
Take an amp reading and compare it to the FLA listed on the motor nameplate.
Look for a poor connection at the breaker.
The chiller load may be increasing as it runs.

 

[Jraef]

You didn’t run the motor in hand as long as it ran in auto.
Take an amp reading and compare it to the FLA listed on the motor nameplate.
Look for a poor connection at the breaker.
The chiller load may be increasing as it runs.

Or, in a similar vein, in "Hand" you are just running the fan, but some sort of damper is not opening, so the motor is basically unloaded. In "Auto", whatever is controlling the motor starter is also opening the damper and the fact that the motor is under sized for the flow becomes exposed. Look for some sort of damper control and it might be as simple as someone having adjusted the damper to open too much. Load = flow, so too much flow = overload.

 

[Aleman]

Just put a clamp on it and play with the damper and set it a bit under FLA. Dampers on fan systems are like power controls. Turn up the air flow the current will climb.