GFCI tripping

[nizak]

Customer calls, has a 240V pool pump that quit running about 3 weeks ago. He proceeds to tell me that the pool tech came out and jiggled a float switch that sits in the bottom of the vault that houses the pump motor, it started running and he left. He says the pump worked for awhile then quit again. At this point the gfci that is integral to the timer tripped, owner has left it that way for the last few weeks.I get there and find the J-box in the vault full of corrosion and wire nut connections in terrible shape. I redo the connections, clean out the J-box and restart the pump. It runs for about a half hour and quits, I try to reset the GFCI that is in the timer unit but find out that now it has tripped the 2pole GFCI in the main panel. When I reset the GFCI's and start it, it runs for about 30 seconds and shuts off. When I disconnect the cord to the motor the breakers hold. One thing I did notice was that the motor nameplate calls for 2.3A@230V, I'm getting a reading of 1.74A@240V. Isn't it uncommon for the breakers to even allow the motor to run for 30 or so seconds if there's a fault? Seems that when the motor is "cold" it runs for a longer period of time before it trips out. Any thoughts?

 

[sc upstate]

I had a problem semilar to yours but in a 3 ph motor. I checked the motor bearings and found a rough spot on one side. Replaced the motor bearings and it ran fine.

 

[zog]

Sounds like a ground, what were your megger results?

 

[nizak]

Unable to check motor leads, 3" pvc water line runs directly across the top of the motor J-box, can't get 2 of the screws out. The design of this is extremely poor, plumbing has to be disconnected to even access motor leads and I left my plumbers hat at home today.