Pump rattling at low speed, appears to seize and overheats

[jimmychuck]

So a few months ago I replaced the original 2.5 Hp motor on my Sat-rite Max-e-pro filter pump with a new two speed motor.

Everything seemed to have gone well, the pump was working in both speeds, no issues.

Recently I returned to find that the breaker had tripped on the filter pump circuit. Upon resetting it and turning the pump back on, i noticed a rattling noise. It was much more noticeable at low speed.

I took the pump apart and found a hole in the diffuser so I ordered a replacement and a new impeller meant for the dual speed pump.

I just replaced everything today and when I went to test it, the pump primed fine and was pumping ok at high speed.

It was making some noise but nothing alarming, it sounded like regular pump noises to me.

When I switched it to low speed, however, it started rattling like mad. Very loud. The pump motor sounded as if it was struggling and then it seemed to start slowing down until eventually it was humming only and then it tripped the breaker. Smoke, white smoke (?) started coming out from the ventilation grills at the rear bottom as well and the housing was very hot.

One other piece of info is that when I took the pump apart to replace the diffuser and impeller, i noticed some black residue around the capacitor. Almost as if it had sparked or something at some point.

The motor is two months old at best.

Any thoughts or ideas as to what's going on would be very appreciated!

Thanks,
Santiago

 

[jimmychuck]

Having checked out the video on cavitation, I wonder if this could be the issue.

If so, how would I go about testing the theory? High speed is fine, low speed rattles, overheats, and trips the breaker.

Thanks.

 

[JoyfulNoise]

I'm no pump expert but cavitation is a high speed / low head phenomenon. If the pump operates and sounds fine at high speed then it's not going to cavitate at low speed. True pump cavitation is rarely ever experienced with pool pumps.

It sounds to me like you were sold a bad motor OR there is some blockage in the discharge side of the pump that high speed can overcome but low speed can't. Maybe a faulty check valve somewhere? Too much head loss in the plumbing?

Other experts will chime in shortly.

 

[duraleigh]

Are you confident the pump is hard wired correctly?

 

[jimmychuck]

Thanks for the comments so far.

The wiring is correct, just triple checked it.

 

[jimmychuck]

Well it appears the pump motor is burnt out. All I get is humming when I try to start it up at its high speed setting.

From the way the problem arose, I'm inclined to consider this as a bad motor given that:

1. It worked fine for 2 months without any problems
2. I've replaced the impeller and diffuser
3. There's no debris or obstruction preventing the impeller from spinning

I believe I can get a replacement motor under warranty but would appreciate any thoughts on the problem as I would hate to replace the motor only to run into the same problem again two months later.

Additional reference points:

• When the pump operated at low speed, I did not observe any air in the pump basket, prime was maintained throughout
• I recently replaced the filter cartridges on the filter so it shouldn't be causing a flow issue
• Check valve on the intake side is flowing correctly

If there was blockage or flow issues on the intake, what would I expect to see?

If there was blockage or flow issues on the return side it would be between the pump and the filter, right? Otherwise I would expect my filter pressure to creep up, correct?

Any comments or guidance would be greatly appreciated.

Thanks,
Santiago

 

[mas985]

Sounds like something is interfering with the impeller which caused the motor to overload. Did you ever run the motor with impeller removed from the housing to see if it had any sort of wobble or noise?

The other possibility is the housing is warped and might be causing a misalignment somewhere.

All I get is humming when I try to start it up at its high speed setting.

That is often a start capacitor gone bad. Can you spin the motor shaft by hand without a lot of resistance?

 

[jimmychuck]

Thanks Mark, I'll take a look when I start pulling everything apart again.

When I disassembled the pump the first time, I found the motor spun without issue and that there wasn't anything blocking the impeller, which was what I thought might be going on.

When I replaced the impeller and the diffuser everything seemed to spin just fine as well. The pump did run for a few minutes at high speed without any problems, but when I went to low speed is when everything went haywire.

I'd hate to just replace the motor and end up with another failure in a couple of months.

 

[jimmychuck]

So I took the pump apart this morning and I couldn't find anything impeding the impeller, no debris, nothing stuck, nothing to indicate that something prevented it from spinning.

I've to a warranty replacement on the way and prior to putting everything back together I plan on flushing the main drain line and the line from the pump to the filter just to be sure nothing is lurking, but I can't help thinking that this was all due to an internal problem with the motor.

When I removed the diffuser I spent some time spinning the impeller trying to see if there was any perceptible wobble as Mark suggested but I couldn't detect any. One thing I did notice, though, was a piece inside the motor housing (I could see it through the vents on the housing) that sits at the front which seemed to be wobbly, almost as if it wasn't on completely perpendicular to the shaft.

As I spun the impeller I didn't hear any noise, either, but I wasn't spinning it anywhere near the 1750 rpms that the motor runs at on low speed.

If anyone has any other thoughts, I welcome them, but for now I'm going to just consider it due to it being a bad motor.

Thanks,
Santiago

 

[JoyfulNoise]

Please update the thread when you get the new motor installed. It will be a good way to close the thread if everything works

 

[jimmychuck]

Well I finally got the replacement motor in yesterday and reassembled everything this morning.

Pump seems to be operating fine and it feels quieter than the last motor so perhaps it was indeed a problem with the first motor.

Will continue to monitor it to make sure all is ok, but for now it seems like all is well.