IntelliFlo VF - cannot run low flowrates, filter status 0%

[nocturnalocean]

Hi everyone! This is my first post on TFP. I'm hoping there are some brilliant minds out there that can help sort out some issues I'm having with my IntelliFlo VF...

My IntelliFlo cannot seem to run any flowrate below 30gpm, and this is only possible with the APC connected - without the APC the minimum flow jumps up to 40gpm! Having done several meterings on my pool circulation system, it seems that this issue has more to do with either rpm's or dynamic head than with flow: for example the above flowrates both happen at around 1420rpm and usually about 8ft of head - anything less and the pump continues to ramp down speed until it either reaches 895rpm, or indicates "system block" at around the same rpm. The pump also begins to shake below these parameters.

The clean filter status also always remains at 0%, despite doing a proper backwash cycle (on the IntelliFlo - cartridge is cleaned by hosing down) ; the pressure gauge on the filter does indicate an increase, as do rpm's/wattage over time. I only mention this because I think this issue may be related. My PB was convinced that the drive is at fault and had it replaced. The flowrates/rpm and pressure readings (TDH) are all the same with a clean filter, and the clean filter status still remains 0% at all times.

I have experimented by removing the cartridge filter element, the APC, the return line attachments (1x aimflow and a PoolSkim), even temporarily replacing the suction line/return line with cheap 2" pipe straight to the pool to try and isolate a plumbing problem. It was also suggested that I check the impeller for blockage - I dismantled the volute assembly, and did not find any blockage or anything else that would indicate an issue.

The pump was installed long after the pool was built (i.e a retrofit). The plumbing was terrible, and I set about designing an efficient layout and upgrading it. Initially I replaced the 2" suction line with 2.5" (2x 45* elbows) - eliminating 8 hard 90* elbows. At the same time I replaced a section of 2" return pipe from the pad to the pool edge with 2.5", including the Tee where the line branches to the 2 eyball returns in the pool. The next upgrade was replacing the old 3-bag sand filter with a 70ft^2 cartridge filter. I could not properly plan my layout without removing the sand filter 1st, so I ended up redoing the entire pad layout. Each time I "improved" my plumbing I got better flowrates at the same wattage, but each time I also lost lower flowrates. Initially I could run as slow as 22gpm, then 26gpm, and now 31gpm is the slowest possible flow. Again these flows correlate with about 1400-1450rpm.

The improvement allows me to complete my required turnover sooner @ the same wattage per hour, thereby supposedly saving me $$. The problem is that I cannot reduce my circulation time (8hrs per day at the moment) without having water chemistry and algae problems - also the filter would work better if I could maintain slower flowrates. Ideally I would run @ 15-20gpm for filtration, and bump up to 30-35gpm for skimming and the APC. On my 8500gal pool (x1.5 turnovers) that would be 1hrx2 for skimming/APC, and 9-11hrs for filtration = 11-13hours total. At the moment the best I can do is 30gpm for 8hours with the APC connected and running full steam all day every day.

Anyone else have similar problems? Any ideas what to do to correct/improve the situation?

 

[JasonLion]

Re: IntelliFlo VF - cannot run low flowrates, filter status

This sounds like a question for mas985, our local pump expert. My guess is that you have lowered the flow resistance so much that the pump has moved outside it's efficient operating range. The pump needs some minimum flow resistance or it won't work correctly. That would then interact with the fact that it isn't very good at measuring flow rate when the watts are too low, and cause something similar to what you are seeing. I am guessing a little here, it is difficult to be sure without more info and some calculations.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

Some more info: The pump inlet (suction) is about 1ft above water level. The top of the cartridge filter is about 3ft above water level. All turns are made by 45* or sweep 90*, with the exception of the return branch (tee) and the 2x 90* turns to the eyballs.

I have attached some photos of my setup, as well as system curves from metering.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

Attached is a spreadsheet for several scenarios, including with/without the APC and temporary replacement suction/return plumbing. All meterings that include the filter element were limited to 50gpm to prevent damage to the element.

 

[mas985]

Re: IntelliFlo VF - cannot run low flowrates, filter status

One thing I see from the data is that the suction head is very close to the return head which can cause cavitation under the right conditions. But I have a few questions and a suggestion to confirm:

How are you measuring the suction head?

What is the filter model?

Also try this with your normal configuration:

1 - Set the flow rate to 50 GPM.

2 - partially close the return valve so the filter pressure doubles.

3 - Now try dropping the flow rate to 20 GPM.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

Hi Mark - Thanks for the reply.

The filter is a Speck BADU Eco Wise 4 (Cartridge) Filter - thats the 70ft^2 model rated for 20 000 - 25 000 gal pool (my pool is 8 500 gal).

I measure the suction head with a gauge @ the pump drain plug (the one at the bottom of the basket). It's a cheap pressure gauge that I modified, but I tested and calibrated it against the pressure gauge on the filter, so I am confident that the readings are at least as acurate as the filter gauge. The reason for this is that I was unable to find a true vacuum gauge locally. It is entirely possible that the vacuum reading is not strictly accurate at the higher end though...

I will do the test you suggested in the morning and post back the result. I do know from doing this to try and test the "clean filter status" on the pump that the rpm and wattage increase. In theory that would allow me to run at a lower flowrate, but likely at the higher power overall.

 

[mas985]

Re: IntelliFlo VF - cannot run low flowrates, filter status

I will do the test you suggested in the morning and post back the result. I do know from doing this to try and test the "clean filter status" on the pump that the rpm and wattage increase. In theory that would allow me to run at a lower flow rate, but likely at the higher power overall.

The intent of the test is to find out exactly what may be going on and not necessarily as an alternative to normal operation although if it does behave well as expected, then we know the problem is an imbalance in head loss between the return and suction but there may be efficient fixes for that.

BTW, what are the size of your return eyeballs? Also, what is the actual model # for the pump?

EDIT - After reviewing some of your test data, I found some anomalies. There is way too much ancillary equipment which is confusing the situation so when you do the test, please remove everything is not part of the basic pool setup. Skimmer basket is ok but no cleaners or add-ons. I think that is similar to your tests starting on line 25 of SS? BTW,why do you need all of the extra add-ons? They may be self defeating.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

I have done the test as suggested. I was not able to get a reliable result @ 20gpm: 20-25gpm all give me 895rpm (25gpm gave a different result initailly, but eventually ramped down to 895rpm), which is a number I have seen time and time again as a minimum speed when the pump spirals down. I added a pic of the result - the blue line is the result before closing the valve (about half-way) [attachment=1:28luo347]Return valve partially closed test.jpg[/attachment:28luo347]
One thing that stood out for me with the APC removed at 50gpm, is that there is a lot of air and bubbles swirling around in the pump basket, as well as the noise accompaning it. When I closed the return valve to double the filter pressure the bubbles and noise subsided almost entirely. Another thing I noticed is that at very low speed (e.g 400rpm in manual rpm) the pump feels as though it is pumping a lumpy substance - it seems as though the motor is not actually spinning smoothly like a top, but rather stepping like a petrol engine (on each ignition) if you could see it in slow-mo on a high speed camera...

I believe the IntelliFlo VF model is 3050 (that's what's on the manual) - I have attached the serial sticker just to be sure[attachment=0:28luo347]IntelliFlo VF-3050.JPG[/attachment:28luo347]

I am not sure what is regarded ancillary equipment. In South Africa it is the norm to leave an suction side APC connected 24/7, and because most residential pools only have one skimmer (occupied by the APC hose) it is common to have a pressure side skimmer attached to one of the returns (eyeball=aimflow). The reason for this is that in summer we often have heavy rain ; in autum we have a lot of wind and leaves ; and in winter we have fairly dry/dusty weather. As most residential pools don't have floor drains or in-floor cleaning, this means that most of the year an APC is neccesary almost daily - a pressure side skimmer (Pool Skim in my case) adds very little resistance overall, but keeps my skimmer basket free from leaves, which ultimately saves me money overall by the IntelliFlo not having to compensate for flow restriction.

[EDIT] Another reason for having the APC connected is that without the APC the minimum flowrate increases to 40gpm, completing the required turnover in 6 hours. This is not desireable for water chemistry and circulation, giving me green algae on the walls of the pool - as-is 8 hours is touch-and-go, I would actually prefer to increase the total circulation time. If I can access the lower flowrates I would leave the APC connected, but set the APC valve to a higher flow. This way the APC would not run (at most it would crawl) for normal circulation, and features would programmed on the IntelliFlo to bump the flowrate up to the required APC flow for a short time twice a day. Depending on the efficiency of this setup I would consider my setup satisfactory. If not, it may be possible to add a dedicated suction line with an automated valve to achive the same effect more efficiently (this would make the pressure-side skimmer redundant, as the regular skimmer would be available to do it's job)- this would only be possible if and when the pool gets replastered, and I consider this a prohibitively expensive solution. Alternatively, having the lower flowrates available would also enable me to leave the APC disconnected, which I would then only connect in the afternoon or every second day or so. As-is these scenarios are not available to me.

 

[mas985]

Re: IntelliFlo VF - cannot run low flowrates, filter status

One thing that stood out for me with the APC removed at 50gpm, is that there is a lot of air and bubbles swirling around in the pump basket, as well as the noise accompaning it. When I closed the return valve to double the filter pressure the bubbles and noise subsided almost entirely.

That is a little odd since it should be the opposite. More air when a cleaner is attached but the suction at the pump is higher. It could be the skimmer is sucking air without the cleaner. Look into the skimmer and see if there is a vortex or the skimmer is emptying.

I am actually able to simulate your test results based upon your description of your plumbing so the pump seems to be operating as it should except for the blockage alarm. This could be due to the plumbing if you have something that changes with flow rate such as a check valve.

Otherwise, it has to be the pump. Either the motor or perhaps something in the wet end. Did you or the PB inspect the wet end, impeller and diffuser? Also, have you checked the line voltage into the drive?

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

When metering the system I always keep an eye on the skimmer if the APC is not connected as it annoys me when air gets sucked in, meaning I have to purge the filter and wait for the pump to settle. When I did the test I kept going over to the skimmer to prevent a vortex from forming (@ 50gpm it does want to...). I have clear pipe between the pump and filter - so I see any air entering the system immediately if I am at the pad. The water level in the skimmer did not drop/empty.

To clarify - when I did the test I did not have the APC connected @ 50gpm and have the bubbles in the basket dissipate when disconnected it. I removed the PoolSkim and the APC before doing the test. There were lots of bubbles swirling in the basket (not just the lid) @ 50gpm (no APC) with the return valve fully open, and almost none when I partially closed it to double the filter pressure. At high rpm/flowrate (lets say over 1600rpm or over 40gpm in most cases) there is usually air entering the pump basket - I have always assumed that there must be a flexible seal somewhere sucking air (bubbles go away at lower speed/flow), but have as yet not been able to isolate the location/cause.

When I did the test I left the lid that keeps the weir basket down in place. I redid the test without the lid.[attachment=0:fvcqxk92]Return valve partially closed test2.JPG[/attachment:fvcqxk92]

Again I could not achieve 20gpm, but had some difficulty finding the minimum this time round. 20gpm & 30gpm both gave me my magical 895rpm with the same pressures as before. Entering any speed lower than 40gpm did not make the pump ramp up speed from 895rpm at all. Going down from 40gpm to 38gpm caused the pump to drop speed to around 1000rpm, and then over the next 15 minutes continued to slowly ramp up to around 1450rpm (down 5 rpm, up 10rpm, again and again). I got impatient and entered 33gpm, which eventually settled to a consistent speed. Finally I set the pump to 50gpm again, left it for a while to settle down - then I fully opened the return valve again, paying attention to the difference in the bubble sound. The noise increase immediately, but subsided again after a while. I think there was more sound with the valve open, but it was not as pronounced as the previous test. The bubbles were definitely less than the previous test, the bubbles were not always visible this time.

I opened the pump myself - it was suggested by a Pentair technician on PoolFYI to eliminate a blocked impeller as a problem.

I do not have any check valves in any part of the system. My pump is 1ft above water level, so not high enough to cause priming issues, and obvoiusly not low enough to flood. The APC valve changes with flow (essentially a bypass valve regulating the APC speed), but thats just to prevent the APC from escaping to the garden! However with the APC disconnected I cannot think of anything that would change with flowrate.

I suppose the next thing to do is test the IntelliFlo @ the pool edge with bare minimum plumbing - any ideas for a benchmark configuration? I am considering doing this with valves at either end to manipulate flow, but am not sure what to test or which values would mean what exactly. This could confirm if the pump itself is performing as it should in a perfect environment - if it doesn't I guess I'll be off to Pentair to get it sorted (100mile round trip )

[EDIT] - I have never had grounds to suspect any voltage problem at the pad, wouldn't the IntelliFlo pick this up? I will test the voltage tomorrow...

 

[mas985]

Re: IntelliFlo VF - cannot run low flowrates, filter status

What about the line voltage? Has it been measured and monitored?

Also, during the last test, what was on the two return line outputs. Eyeballs or just open ended?

As for testing the pump at pool side, you really need to be careful doing that because it is easy to exceed the run out flow rate so I would not recommend doing that. Beside, that is not a typical plumbing environment. In fact, the first test in the table without any return restriction is about as ideal as you can get. There is nothing to suggest that what you have is not typical except that the filter is a little small. So you might try again without the cartridge but I don't think that is going to change anything.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

I have not had reason to check the line voltage - I will check that tomorrow (11pm here now...).

I have done a metering without the filter element (All removed in the system curves). I was considering making up a pipe section to take the place of the filter housing for the next time I chemically clean the filter element (I don't have another ideally sized container). Then I can meter without the entire filter included, but I doubt this will be significant. The test I did with a temporary return line gave me a significantly flatter curve, but did not give me access to the lower flowrates I am not getting now.

The return lines for both tests: PoolSkim removed (it has an insert - ID is about 1.5"), second return has an eyball (either 3/4" or 1" - not sure which I had in there last...).

Wrt the pool-side test: Glad to know about the run-out, had not considered that! Guess I won't be doing that...

The filter is 70ft^2 and rated for a pool 3-4 times bigger than mine (20-25k vs 8.5k gal)?? For future reference, what size would you recommend for a 8 500gal pool running an IntelliFlo VF? FYI - I would definitely opt for a side (mid-height) inlet next time round as opposed to the bottom port versions...

Any ideas about the clean filter status always being 0%? Might this be related to the flow issues discussed so far? How about the 45* elbow at the pump inlet - would that cause the issues at lower flowrates, or would that effect be consistent throughout? The skimmer connection is 2", could that be a problem - would adding another suction change the situation as it stands? What about adding another return line (like a weeping wall)?

 

[mas985]

Re: IntelliFlo VF - cannot run low flowrates, filter status

Pool size is only one factor when sizing a filter. For optimal filtering, a cartridge filter flow rate should not exceed 0.375 GPM/sqft or in your case, 26 GPM which is a very low flow rate. If your max flow rate is going to be 50 GPM, then you want a filter that is at least 133 sqft or about twice the size you have now. Forcing high flow rates through a small cartridge filter reduces the life of the cartridges.

As for the 0% filter. I believe that means the filter is clean. It goes up to 100% when the pressure rises 14 PSI or whatever it has been set for. Read through the manual, it describes all of that plus the alarms.

http://www.pentairpool.com/pdfs/IntelliFloVF%20OM.pdf

In fact, you should review all of the settings to make sure there isn't something set wrong.

Also, you can run the pump in manual mode to override all of these "features" just to see if it works properly.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

Thanks for the filter sizing info - I was aware that pool size is not the only consideration, but did not know any calculation criteria for proper sizing. The Speck cartridge filters were more affordable at the time I needed to replace the sand filter, so I chose the biggest one I could get (which, as I mentioned is 3 times oversize by pool volume). That being said - if I can sort out the issue with minimum flow, I could program the pump in such a way that I would not generally not need more than 26gpm.

I am familiar with the manual - as I am a tech fan, I read it cover to cover when the pump was first installed. The settings the PB first set the pump to were not ideal, so I referenced the manual again to learn how to meter and program the IntelliFlo more optimally. While we still had the sand filter the clean filter status functioned normally (it raised about 40% each week - the sand was fairly well graded). I did run into an issue with the sand filter short-cycling at one point, which sorted itself out once I realized that someone other than myself had fully closed the APC valve - not sure why this caused the filter pressure to build up to near 100% within an hour or two, but the problem went away the moment I tuned the APC valve to what it should be. At one point we had a severe storm, which flushed mud and debris into the pool. This overloaded the filter, putting the pump in "service system soon" for the first time. After the filter was backwashed a few times the following day, I don't recall the filter status ever changing from 0%. Since I did the 1st plumbing upgrade soon after this, I am not sure whether this event caused the issue, or if the new plumbing is the cause. I am aware that even with a cartridge filter it is still necessary to run the backwash cycle on the IntelliFlo each time the filter is cleaned, in order to reset the clean filter status. I did this every week for the first year while we still had the sand filter, and still do this each time I reinstall the filter element after cleaning it. After about a month the pump runs at higher rpm & wattage and the filter gauge shows an increase in pressure (not due to air in the filter - I bleed any air once in a while, never a lot in there) - this clearly indicates that the filter is indeed backing up (getting dirty). So I clean it, and the rpm/wattage and filter pressure go back down to normal. The clean filter status remains 0% all the time no matter what. I tried to simulate a dirty filter by partially closing the return valve - rpm/wattage/filter pressure increase, but clean filter status remains 0%. I figured that the IntelliFlo might pick this up as a temporary increase, so I ran a backwash cycle, left the pump running the usual schedule for a day and then partially closed the return valve. I left the return valve partially closed for another day, and voila - clean filter staus is STILL 0%. Closing the return valve further, pushing the filter gauge to the 100% mark (clean filter pressure +200mbar) promptly puts the pump into "service system soon". This has also happened with an algaecide that had a flocculant in it, blocking up the cartridge filter - "service system soon", maintaining the pressure the pump was programmed to indicate a dirty filter. While the algae was being treated I kept an eye on the filter pressure at the filter gauge - it climbed rapidly from one day to the next, but filter status on the pump did not change. The PB figured the IntelliFlo drive was faulty, and had the drive swopped out. This did not resolve the issue.

I will go through all my settings in the morning. As the drive was replaced I would have needed to duplicate my mistake in order for the settings to be at fault. I set the pool volume (56m3 = 1.7 turnover = 7m3h over 8hrs), 1 turnover, 1 cycle, current time, the filtration cycle (9am-5pm), max prime (8m3/h, 1min), filter status (200mbar), units (*C, m3/h), temp 20*C, backwash/rinse (1min each @ 8m3/h). No features are enabled at present. What should I be on the lookout for?

I use manual mode to meter the system, which is how I produced the system curves. I use set flow to meter the system, and set rpm to tune the APC valve (the gauge and the APC have different resistance, so set flow is not appropriate - I know the rpm beforehand from Filter Mode, as well as my system curves). The pump behaves the same for manual flow as it does in filter mode. Symptoms such as air in the pump basket occur in set flow same as in set rpm (at the same rpm), as does vibration/shaking for flows/rpm below 1400rpm (which I cannot achieve in Filter Mode or set flow). As far as I can tell the issue is not isolated to Filter Mode.

 

[nocturnalocean]

Re: IntelliFlo VF - cannot run low flowrates, filter status

I measured the voltage today: I got readings ranging from 233-243V - the fluctuation may have something to do with how well I was making contact with the leads of the meter. When changing speed the voltage fluctuated more, then becomes more stable. Voltage also appeared more stable with the pump either off or at high speed (2400rpm) ; and most unstable at very low speed (400rpm). I would have liked to also measure current to verify the wattage indicated by the display, but apparently my multimeter cannot measure AC current. [EDIT] - I did a second measurement for consistency. I found out later that our tumble dryer in the house was running while I did both tests - not sure if another inductive load somewhere else in the house would influence the readings I got... FYI - our power is single-phase (I was told the IntelliFlo converts this into 3-phase...not sure if this matters).

Pump off: 239-243V / 237-240V
2400rpm : 235-239V (926-929watt) / 241-242V
1400rpm : 236-241V (221-225watt) / 238-240
400rpm : 237-242V (127-133watt) /236-239V

Are the voltages above normal? They are within the 90-110% from 230V range specified for the InteliFlo, but I am unsure if the fluctuation is normal. Would line conditioning be beneficial, or would this work against the electronics of the InteliFlo drive?

My apologies if my previous post seems somewhat crude or impatient - consider this an indication of my frustration in getting to the bottom of the issue at hand. I highly value and appreciate (and therefore defer) on all points to the expert opinions offered in this forum. Thank you very much! :-D

I believe the return is at water level near the pad (water dripped out below ground, near the pad, when I last worked on the return line - had to plug the eyeballs) and is about 1/2ft below water level at the pool. Could back-pressure from the pool volume cause issues with lower flowrates?

 

[markmac]

Re: IntelliFlo VF - cannot run low flowrates, filter status

nocturnalocean, did you ever resolve this? I cannot run low flow rates either as I experience the same symptom as you with the vibrations below 1400rpm. Pentair has replaced the impeller and diffuser ( as mentioned above by mas985 as a potential). However that did not fix it.

I never thought of checking the line voltage, but now that I read this post, I know the watt reading on my VS fluxuates significantly at the lower speeds, unlike the high rpm.