pool pump turns louder every 6 minutes, lasting for 2 minutes

[stobit]

Pentair Intelliflo variable speed pump turns louder (it is about 50% more sound, but quite noticeable since it is not like normal pump motor white noise, but more like "grinding" sound or with some tones (no high pitch tho), or like the sound when pump runs at much higher speed.
Pump is set to run 1850 rpm daytime.
The louder sound follows very regular timing, the pump is quieter for every 6 minutes, and then turns louder for 2 minutes, over and over again and keeps accurate timing pattern.
What could cause this？A gradually broken bearing? Or some leakage triggers auto-priming periodically?

The pump is set to be very low speed after 11pm night time. But even after it lowers rpm at night, the same periodical loader sound happens in the same time pattern. and it is much more noticeable than daytime since at night it only runs like 1000 rpm and very quiet. But like daytime, every 6 minutes it turns as louder as the same level of day time and lasts for 2 minutes before it turns quiet again. over and over again.

Thanks a lot for any help for this mysterious behavior of the pump!

 

[mknauss]

Welcome to the forum!
When this happens, does the rpm increase? Do you have the pump hooked up to an automation system?
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[stobit]

Thanks for the reply.
The problem is this is for our community pool but my home is closest to pump room and suffers most from its noise.
I don't have direct access to the pool pump room. I talked to the maintenance people and they claimed everything is fine (as always!) and didn't see rpm increase.
pump is programmed through its own controller (no third party/additional control loop). The program is basically 6am to 11pm 1850rpm, other time 1000 rpm
There is a large priming noise when it varies its rpm at two time points, but priming only lasts less than one minutes.
This periodically loader noise is much less than priming sound (when pump ramps up to about 2400 rpm) , but still noticeably larger than normal operation.
The most weird part:
It is louder for 2 minutes, quieter for 6 minutes. I can even use it as a wall clock!

Welcome to the forum!
When this happens, does the rpm increase? Do you have the pump hooked up to an automation system?
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[Rich D]

Can you hold your hand in front of a return to see if it is a rpm increase? I do not see how It could be a mechanical issue with that much consistency. I would guess the control is where the issue will be found.

Has it always done this or is it something new?

 

[Rich D]

It almost sounds like a freeze protect option not working correctly.

 

[BowserB]

Pentair automation suffers, I think, from the right hand left hand syndrome. I have a Pentair Intelliflo VSF connected to a Pentair Intelliconnect. The pump would shut off and restart every day at 11am and 7pm. Spoke with Pentair's Engineering Manager--who happened to be the guy who sees every service request. He had no clue. I checked the four app-settable programs and also the other four panel-settable programs (those were disabled). We were at the point where he would give me the "back door" reset sequence to set the pump controller back to factory defaults. Then he spoke with the firmware programmer and found that Pentair sends out a time sync to all intelliconnect boxes at 11am and 7pm. The Intelliconnect box in turn sends a time sync to the pump controller, which then restarts if running.

My point? The source of the bizarre behavior may lie outside the pump controller and maybe outside the local automation. The six minute cycle, though, could be something that a factory reset might fix. A Pentair-authorized technician may have to look at it, though, as the company is pretty careful about who knows the back door reset sequence.