Got a service call while at a supply house. Older man said that his pump (1 HP 120 VAC Hayward) had tripped his GFI and wouldn't reset. So he changed the GFI and it still tripped. Okay, I figured that he installed it incorrectly. Got to his house and it was a dedicated 15 amp circuit with the GFI wired correctly. PVC pipe from the panel, to a switch, then to the box for the GFI. Here's what transpired: changed GFI, still tripping. (Initial start current 17.5 amps (for about half a second), then settles down to 10.8). Ran temp 14/2 from panel to GFI, still trips. GFI in garage runs pump without tripping. Gremlins or...? Thanks, petey.
Pete, You own a Megger? What I would do is disconnect the motor, open the terminal box up, disconnect the C-switch and megger the Start and Run windings to Ground. That should give you an idea of what is going on there. It sounds to me like you have a winding down to Ground within the pump motor.
With it being a 120V motor, you should only use a 250V megger test.
Trumpy, I'll borrow a megger from my other job. This pump is only three years old. We thought it was probably going south due to all the rain we've had here this past few weeks, but when it didn't trip the other GFI... I just didn't want the customer to spend $400-500 for a new pump to have the same problem arise.
If it was water I would expect the problem to clear if you ran the pump for a while ... at least until it rains again. I know the drill I use to mix mortar and grout will trip the GFCI if I get it a little wet but if I take it to a non-GFCI and run it for a minute or two the problem goes away.
This is why I thought of gremlins...: Dedicated 15 A 120 VAC ckt. to SP switch to GFI (GFI 1) near pump location. Changed customer supplied GFI (GFI 1 to my own GFI 2) - still trips. Runs okay on another (older) GFI (GFI 3) in garage on extension cord. Bypassed switch - still trips. Bypassed entire run from panel to GFI, still trips. Changed breaker (getting desperate...) - still trips. Runs okay on non-GFI receptacle (and draws 17 + amps for a half a sec or so). Ground and neutral connections good. Replaced GFI 3 with GFI 2 and it runs okay. (cue spookey music....)Thinking about going to a GFI breaker....
Petey, I think that the 1HP pump at 115V should be on a 30A breaker, but the system might squeek by with a 20A breaker. I don't think that its a ground fault issue. The #14 wire is ok, but my Square-D motor sizing chart says that the breaker should be 30A.
Below is a link from Square D so that you can download an IEC Motor Data Calculator and other small but helpful product selection programs. Hope this helps.
When you tested the pump with the first and second GFI in the garage(GFI 3 & GFI 2), was the pump still connected to the pool water? Perhaps the ground leakage path is thru the pump shaft, into the pool water and to earth via the pool ...
Obvious question: Can you verify the connection between the ground pin of the pump cord plug and the pump & motor case?