Pentair Intelliflo VS shuts off at low speed

[jzelno]

I have a 3HP Intelliflo VS pump that is about 6 years old. It just recently started failing at low speeds. The pump will attempt to turn on and prime, then when it switches from priming to low speed mode (1600rpm), it will do fine for maybe 10-20 seconds, then it starts vibrating a little, then it shuts off with an overcurrent error. This repeats every 20 seconds or so. At higher speeds (2400rpm+), it seems to run just fine. There doesn't appear to be any problem with the plumbing (I get good suction at the inlets, and the outlets have a good flow, and the DE filter pressure gauge is in a normal range). I thought the impeller might have been clogged, but it's clean. The motor seems to spin OK, and the seals under the impeller look OK as well. Any ideas about what can be wrong or how to fix this?

Thank you.

 

[Jimrahbe]

J,

I know it is of no help, but in the more than five years that I have been here, that is the very first time I have heard of that specific failure.

If no one else chimes in, then I'd call Pentair. I suspect the motor control head has some kind of issue, but that is just a guess.

Thanks,

Jim R.

 

[JamesW]

Is the seal plate in good shape?

Are the brass grommets ok?

Is there evidence of the impeller rubbing?

Can you show pictures of everything including inside the pump?

 

[CA92807]

I had the exact problem with my Pentair 011018 at just under 6 years. I found that it worked ok warm but when cold (I'm also in SoCal, so that's below 50F), the vibration occurred after the pump slowed from start mode to low speed. I first thought it was due to an imbalance but it turned out to be a problem with the controller. I purchased the pump with a credit card that offered an automatic warranty extension and was able to get a replacement.

 

[jzelno]

I did call Pentair, and they suggested I see what happens when I run the pump a little faster or a little slower.
So I tried slower at 1500 and 1400 rpms, and the pump shut down faster than at 1600.
Then I tried 1700, and it was OK
Then I tried 1630rpm. This one was interesting... after about 15-20 seconds, it started vibrating again. Then after 30-60 seconds of that, the vibrations died down and everything was fine again. Also, the display shows a power meter... it would start out around 250W, then as the vibrations started, it would steadily climb up to around 600W, then as the vibrations died, it would steadily decrease back to 250W. After this initial vibration period, the motor seemed to run fine for the rest of the time (I only stuck around for 3-5 minutes, but the motor remained stable during that time).
I called Pentair back after that, and I got a different tech on the line. He suggested that the motor itself was going bad. His reasoning was mostly based on the fact that the motor was vibrating at the low speeds.

@CA92807, You said you had the exact same problem, and it was blamed on the controller. When you said you got a replacement... was it a replacement of the controller module that sits on top of the motor, or the whole pump? If the whole pump was replaced, did you by chance just swap the controllers to see if that helped?

@JamesW, I don't have pictures, and I don't particularly want to disassemble the pump again to do that... sorry. But the seal plate appears to be in good shape, and there are no leaks. The impeller and diffuser and their contact points look fine to me... nothing inside seems abnormally worn. I'm not sure what brass grommets you're referring to... I don't see them on the parts diagram in the manual.

Thanks again.

 

[JamesW]

The grommets are what the motor bolts screw into to hold the motor to the seal plate.

Sometimes the grommets come loose, which makes the motor pull back and the impeller will rub on the seal plate.

 

[JamesW]

The motor shaft has a slot on the end which is accessible through the center of the fan cover. Use a flat blade screwdriver to spin the motor shaft while the pump is off to see if the shaft spins freely with no binding.

 

[jzelno]

Thanks for the picture, James. I did not remove the motor from the seal plate, so I can't see what the brass grommets look like or if they're loose, but the bolts that go into those threaded inserts are all nice and tight, and there's no movement of the motor relative to the rest of the pump when I try to shift it by hand. When the motor vibrates at low speeds, everything vibrates... there doesn't seem to be any more or less vibration happening at either the motor or the pump end.
The shaft spins smoothly when I spin it. No binding. When I had the pump disassembled, I could spin the fan blades by hand, and it would continue spinning for a second or two after I let go.
Other than the vibration, there are no unusual noises coming from the motor when it's running at any speed.

 

[JamesW]

OK, hard to tell exactly what the problem could be.

 

[CA92807]

@CA92807, You said you had the exact same problem, and it was blamed on the controller. When you said you got a replacement... was it a replacement of the controller module that sits on top of the motor, or the whole pump? If the whole pump was replaced, did you by chance just swap the controllers to see if that helped?

The cost of a new replacement controller (with only a 90 day warranty, IIRC) is nearly the cost of a new pump, so I got a new pump and a third-party extended warranty. My credit card paid me the repair cost, I paid the remainder. This happened December, 2018.

If you do a web search you will find other owners complaining about low speed vibrations with this pump. Most assume it's an impeller or mounting issue as I did at first. I discovered, using my whole house power monitor, that the problem was intermittent and cold temperature correlated. If I hadn't had the extended warranty from my credit card I would have waited for the pump to fail as it would finally start working correctly after it warmed up.

 

[Newdude]

My credit card paid me the repair cost, I paid the remainder. This happened December, 2018.

Check with your credit card first. I had this feature and it was taken away shortly before I bought a new refrigerator with it. In the end it didn’t matter but now I check first and swipe accordingly.

 

[jzelno]

The pumps run around $1200-$1300 new. The controller around $800, and the motor around $500. So If I needed to replace the controller and motor, I'd be better off replacing the entire pump. This one was provided free to us by our electrical solar panel company as an incentive (we had a single-speed pump prior to this when we invested in solar power), so I can't take advantage of any credit card warranties, if they might have existed.
I had previously been Googling for "intelliflo low speed shutoff", which didn't yield much, but I did find some more stuff looking for "intelliflo low speed vibration". Thanks for the idea on that. Unfortunately, nothing showed up as an obvious cause/solution.
Also, my problem doesn't seem to be temperature related. It was around 70° when I was trying to troubleshoot this yesterday.
I'm planning on opening up the controller module to have a look around, to see if there's any signs of wear in there. I'm an EE, so I have some experience looking at/for stuff like that. I just have to wait for a set of security torx bits to arrive. I'll report back if I find anything. Otherwise, I might be left guessing whether I should replace the motor or controller in an attempt to save some money, or the whole pump.

 

[CA92807]

I've got a EE background too, so I also opened the controller to have a look. I already had a full set of security bits. You won't get too far. There are some large polar caps that are potted into the housing that must be de-soldered to get to the front of the PWB. I didn't go that far but found a youtube video that destructively accessed the board only to find that the controller IC is custom.

I don't think a motor failure would produce the symptoms I had. They usually fail shorted, occasionally open and I've never seen one that reverted back to OK. I observed 2X high frequency current spikes that corresponded to the vibration. After a while they would diminish in frequency but not amplitude then they would stop and all was well with the pump. And like you found, the vibration signature would change with the speed, and then disappear. I concluded the motor was being driven to produce the vibration. There is some feedback in the control loop as speed and current appear to be monitored (hence the over-current failure notice), but no tachometer that could have been a failure point. So just the current and perhaps the back EMF from the windings are used. I did check resistance of the 3-phase motor and that looked nominal.

You might consider taking the controller off and heating it up in an oven and/or cooling it to see what happens.

If I had to replace my pump again, I'd consider a two-speed unit. I now only run the pump 4 hours a day total at low time of day rates so there is not as much savings as when I first got it.

 

[mknauss]

Be aware that their are motor standards for pool pumps currently in effect in California (and the rest of the country starting this July). So not using a VS motor may not be possible.