Pump motor cycling on and off

[bucketofish]

Hello, pool experts! I have an issue that my pool service contractor hasn't been able to solve.

First, some context: I have a 21000 gal in-ground gunite pool with a waterfall and attached spa. There is a panel inside the house to program the pool; i.e., enter time the pool pump / waterfall / spa turn on and off, etc., as well as operate equipment manually. There is a panel outside the house, near the pool pumps and DE tank (the heater is busted and has been taken out of line). The outside panel overrides the inside panel but has no programming features; i.e., strictly buttons to turn equipment on or off or switch overall modes; e.g. "auto" mode switches to inside panel, "service" mode operates pool equipment from outside panel. We just had a multi-port valve installed during the pool opening this year. It can backwash, bypass the DE tank, go straight to waste, etc. I've backwashed and re-earthed the tank as needed. (The spa motor needs to be replaced, but that's not the issue here.)

We had the pool pump motor replaced in 2014. Since then we've never had a problem with it, and I never touched it. It's supposed to run continuously from when its program starts at 9AM and ends at 7PM. But since opening the pool a few weeks ago the pump motor has been cycling on and off unprompted many times throughout the day - how many and for how long I don't know, as I haven't made the time to monitor it that closely... yet. I've been wondering if it's simply overheating, shutting down and then restarting when it falls below some temperature threshold, then shutting down again when that threshold is exceeded. It's definitely too hot to touch at that stage, but I have no frame of reference because I've never had a reason to touch it before - for all I know it's typical for the motor housing to get that hot... or is it?

We had our pool service contractor send their best tech out to inspect it; btw, this is a guy we know and trust, and was probably the one who installed it. He opened it up, took it apart, found nothing wrong with it, re-assembled it; said he had no idea what's wrong but we could always replace it. I said why replace it if you can't find anything wrong with it. He said keep an eye on it and get back to them if it keeps happening. Well, naturally, it's still happening. I've discussed it at length with them... could be a bad relay in the wiring, could be in the inside panel or the outside panel, who knows. What am I supposed to do... replace every component for hundreds or even thousands of dollars and maybe still not track down the issue??? I already spend $130 and learned nothing. So here I am. Any thoughts? Thanks much for your help!!!

[Teapot]

I think your probably correct, shutting down when too hot, cooling down and restarting. Very tricky to diagnose tech problems from behind a PC.
I would be inclined to separate the pump from all the wizardry, plug it into a power outlet and see if it continues its wayward behaviour.

[bucketofish]

Hi, Teapot, thanks for your input, although I'm told that the act of pumping water helps keep it cool, so I don't think that testing it offline would help.

[Teapot]

Not suggesting you test it off line, just away from your clever electronics and plugged directly into a separate power socket.

[bucketofish]

Thanks again for your reply and attention to my pool issue, Teapot. Plugging the motor into a separate outlet is not an option anyway. The power cable is hard wired from the motor casing through a conduit into the ground.
I considered if it's a faulty relay, but I don't think so. The pool pump is cycling on and off regardless of whether the inside or outside panel is in control. The outside panel makes an audible click when you push the button to turn any mechanism on or off, but I hear no such audible click when the motor has been cycling on and off on its own. So I'm more inclined to think the motor is overheating as earlier described, even though the tech didn't find anything visibly wrong with it during his visit last week. At this point replacing the motor is the next logical step, so I think I'm just gonna have to bite the bullet.

[Teapot]

You haven't described your filter, plumbing and pump size so can't see if you follow the trend of big pump, small filter, small plumbing which not only strains the pump but also the wallet because of the electric bill.
I would replace your pump with a variable speed pump if possible.