Strange pump noise...i'm baffled...

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T

tlevy

0
Jun 3, 2015
355
Ottawa/Ontario
Hi all

My pump makes a strange noise and I am having a real problem diagnosing it - I am hoping TFP folks may be up for brainstorming with me!!

As best as i can describe it, when it is (what I believe) "normal" sounding operation, the pump makes a clean, relatively high pitched sound. As clouds move over the solar panels, the motor rpm reduces as increases. This is because the pump runs directly off solar PV panels (through an MPPT controller).

A few weeks ago we noticed that the pump noise will suddenly change, very occasionally with an associated "rattle" of the sand filter line connected to the pump. When the pump changes, the motor sound goes down an octave - again, as best as I can describe (attached video of lower octave sounding pump motor noise.https://vimeo.com/135932808

When the pump changes sounds, i do not notice a change in flow or pressure. Also, we had the pump inspected and all seals were fine, and the bearings were fine - it was reported as being mechanically fine, with no debris or dog hair in the impeller. We also had, when we took the pump in for an inspection, a suction side leak - we had tried to patch it with silicone and plumbers wrap, which reduced the leak, but didn't eliminate it.

The pump expert (nb, just a pump expert, not a pool guy), mentioned that the suction side leak could be the issue, causing cavitation, or something internal that moves back and forth in the motor housing. Today we repaired completely since the suction side leak. When i fired up the pump it ran normally, with a high frequency motor hum, for a few minutes, but then the pump started to make the sound intermittently, and after a short while, continued to operate continuously with that lower octave operating pump motor sound.

Anyone with any best guesses? I'm running out of things to check, and baffled!

Thanks for taking a crack!
t




68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
 
It's your suction side leak. There is an article in Pool School you may find helpful. If the noise change is consistently rhythmic your pool water level is probably too low (or the skimmer basket is chocked full) allowing the skimmer to suck air.

There should be little to no air in you pump strainer basket.
 
Suction side leak was repaired - whole new plumbing put in. I have also found that air can still remain in the basket if the pump is not powerful enough to displace all of the air - the best evidence of a suction side leak is not air in the strainer basket, but bubbles in the return jets. We also checked pool water level, which is fine as well...


68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
 
I'm not a pool guy, but I know pumps, valves, and associated equipment. Is there a suction valve that isn't open all the way by chance? Perhaps one that appears to be open, but maybe isn't? Does there happen to be a suction pressure gage?

Like mentioned above, it sounds like the pump is beginning to cavitate. Full blown cavitation will sound like marbles in a tin can.
 
the best evidence of a suction side leak is not air in the strainer basket, but bubbles in the return jets.
Click to expand...
Where does that air in the return jets originate? It doesn't start on the pressure side.

Air originates from the suction side of your system and when you find that and fix it, I think all your issues will be solved.
 
Since I no nothing about solar panel powered pumps, I'll throw out a dumb question. I assume the "MPPT" controller controls voltage and amperage to run AND protect pump. So if ALL suction side leaks are addressed, could low solar output (i.e. Cloudy skies) cause the pump to slow down enough to cause cavitation and thus air and associated noises ?
 
Cavitation doesn't fit...
Suction cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure.
Click to expand...
 
lefty51 said:
Since I no nothing about solar panel powered pumps, I'll throw out a dumb question. I assume the "MPPT" controller controls voltage and amperage to run AND protect pump. So if ALL suction side leaks are addressed, could low solar output (i.e. Cloudy skies) cause the pump to slow down enough to cause cavitation and thus air and associated noises ?
Click to expand...

We thought that originally, but it also occurs under full sun too. Your thinking on MPPT is quite accurate - which stands for "Maximum Power Point Tracking", which seeks to maximize output by finding the best voltage and amperage on the panels, based on the load (in this case, the 3-phase DC pump)


68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
 

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I am assuming the motor runs on DC without using any inverters?

Have you had the panels checked out to make sure the line voltage is constant?

Can you run the pump motor on an alternate energy source (i.e. power supply).
 
Line voltage varies with sun, which is cleaned up with the controller. That being said, it is worth checking it out. I can power the pump with a 48v battery but don't have one...


68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
 
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