VS Pump wattage/GPM decreases for a set RPM after 30-60mins

[TaylorN]

I am working with a Jandy VSP ePUMP VSSHP270AUT 2.7HP and PLC1400 SWCG.

Out of curiosity (trying to prove very low speed may have been causing SWCG scaling) I am trying to dial in the RPM of the motor to achieve the 20GPM minimum specified in the manual for the PLC1400 SWCG. So I also installed a FlowVis Flow Meter (to read GPM) in between the filter and heater. I got it for free, so figured I may as well install it.

Here is the weird part. When I set the motor to 2100rpm it will start reading anywhere from ~358-367watts and the Flow Meter will read 19-20GPM for the first 10-15minutes of running, but then over the course of 30-60minutes (I'll take readings every 10minutes), the wattage will slowly start decreasing (along with the GPM) and end up at a random wattage anywhere between ~338-350watts, 15-29watts less than it started. This usually leads to a GPM anywhere from 12 to 17 GPM and seems totally random where it ends up throughout the day. Its kind of annoying when I can pick an RPM and it hits 20GPM for 10minutes, but then when I come back hours later it could be operating at 12GPM or 17GPM.
Besides the oddity of the decreasing wattage, I wouldn't think a 15-30 wattage reduction could contribute up to a 8GPM decrease when the pump initially reads 20GPM. A 8GPM drop from 20GPM is 40%, but a wattage decrease from 367w to 338w is only 7%. How does a 7% decrease in power reduce GPM by 40%? This all seems a little curious.

Is the pump/controller/etc working as expected? If so then I imagine I will just need to pick a higher RPM so it settles somewhere in the 20GPM range after running for an hour?

Southern California energy pricing is crazy, so I want to dial in my pool/life to be as efficient as possible It initially started with odd SWCG scaling, now I am down this rabbit hole... hahaha

 

[proavia]

Post a full set of test results from your K-2006.
The last you entered in PoolMath are a month old.

Also, turn on 'Track CSI' in PoolMath
With a SWG, it is best to keep the CSI between 0.00 and -0.30 to minimize scaling.

Consider adding a heater bypass to your system. A heater usually restricts flow. Using a bylass when the heater isn't in operation will allow a lower rpm for the same flow rate.

Heater Bypass - Further Reading

www.troublefreepool.com

The flow rate after the heater (where the SWG is located) is where the FlowVis would be best located. Although, as long as the flow switch of the SWG is closed, the SWG is happy and will produce chlorine.

What is the minimum rpm to close the flow switch of your SWG? This should be with a clean filter. Find this number and add 100-200 rpm to it to account for when the filter gets dirty.

 

[JamesW]

Its kind of annoying when I can pick an RPM and it hits 20GPM for 10minutes, but then when I come back hours later it could be operating at 12GPM or 17GPM.

Probably a dirty filter.

What filter do you have?

When is the last time you took it apart and cleaned it?

 

[TaylorN]

Post a full set of test results from your K-2006.
The last you entered in PoolMath are a month old.

Also, turn on 'Track CSI' in PoolMath
With a SWG, it is best to keep the CSI between 0.00 and -0.30 to minimize scaling.

Consider adding a heater bypass to your system. A heater usually restricts flow. Using a bylass when the heater isn't in operation will allow a lower rpm for the same flow rate.

Heater Bypass - Further Reading

www.troublefreepool.com

The flow rate after the heater (where the SWG is located) is where the FlowVis would be best located. Although, as long as the flow switch of the SWG is closed, the SWG is happy and will produce chlorine.

What is the minimum rpm to close the flow switch of your SWG? This should be with a clean filter. Find this number and add 100-200 rpm to it to account for when the filter gets dirty.

Hey there @proavia!

I updated my readings in Poolmath (I don't have a subscription so it only shows one log). And I have 'Track CSI' on, but does that only work with a subscription?

One note is that if I drop the pH to 7.2, it usually creeps back up to 7.6 in 7 days. So I could have a Tuesday log and a the following Monday log and the only difference would be the climb in pH

As per your CSI (-0.30 to 0.00) with SWG recommendation, that is pretty much what I was thinking, and now trying to pivot to achieve a lower CSI (from what it was previously), but I don't know how to get the CSI consistently in that range. The only variable I can really control (without dumping water and adding fresh) is to somehow lower the Total Alkalinity, but I don't know how to do that while maintaining a 7.4-7.6pH (better for the eyes?) How is that accomplished? I have read some things about reducing the pH to 7.0 and then using aeration to raise the pH, which might keep the Total Alkalinity lower, and to keep doing that until I can get a TA of 80(?) Is that technique even possible?

And for the Heater bypass idea.... That sounds awesome and never thought/read about that before! Thanks for sharing the link. However, the only thing that sticks out in my mind would be that I thought at lower RPM/GPM the friction is reduced, so a bypass might only make sense with high RPM/GPM. If that is true, then having a bypass when trying to achieve better efficiency at lower RPM/GPM doesn't really make sense to me. At lower flow I would think the Heater wouldn't be much of a restriction?

And as for placement of FlowVis, I was just following the manufacturer's recommended locations. I could have put it post heater and pre SWCG but it would have been harder to plumb it in. Plus, does it matter? Don't you have the same flow rate if you measure anywhere after the filter anyways? I know there are restrictions, upstream of the current location, but if the flow gets reduced upstream wouldn't it also be reduced in the current location as well? I probably don't understand the physics with water pressure vs GPM.

Lastly, I tried reducing the RPM of the pump all the way down to 700rpm (18watts and maybe 0.5-1.5GPM), but the Jandy Aquapure flow sensor never gave a warning. It said it could detect flow and never stopped the SWCG, which is strange. At some point a few years ago I did the same thing and was able to get a flow error at 700rpm, but not at 800rpm. 800rpm seems awful low. The pump is literally consuming 18-25watts and I can only barely feel flow out of the returns if I stick my finger in the hole and can barely feel a trickle of water flowing past. Either I am doing something totally wrong, or the Jandy Aquapure is not registering flow correctly. There is no mechanical switch, its just the electronic sensor that with two probes that measures salinity, temperature, and if there is flow or not. I don't think it tells you went it has the ideal flow for the SWCG. Like I said in the other thread, Jandy recommends ~20GPM for their SWCG (PLC1400)

I am just all sorts of confused

Thanks for the continued support and recommendations

 

[TaylorN]

Probably a dirty filter.

What filter do you have?

When is the last time you took it apart and cleaned it?

I honestly can't remember exactly. Could have been 6-12 months ago, not more than that, and probably more like March. Plus we have an automated pool cover, so there shouldn't be much debris. But I can try to clean the filter and see if that has an effect on the weird wattage/gpm decrease. Man, that is just eating me up. This afternoon I was turning it on and off testing different RPMs etc. But ultimately its still unpredictable (within reason). This morning 2100rpm would start at 360watt and drop to 335watts, and this afternoon it would start at 380watts and drop to 355watt. It consistently drops a certain amount of wattage, but it all depends on where it starts wattage wise. And the drop in GPM directly corresponds to the drop in wattage. GPM might start at 20GPM@2100rpm in the morning and when I restart it (turn off/on or just change from one rpm to another) in the afternoon it may start at 16gpm. So weird. Nothing else is changing. I even unplugged the underwater "The Pool Cleaner" from its suction hose in case the deep end suction was different from shallow end suction.

Photo of Jandy CL460 attached

Thanks!

 

[JamesW]

What are the filter pressure readings at different power levels and different flow readings?

I suspect that the filter pressure is going up causing more restriction and causing the flow to decrease.

 

[TaylorN]

What are the filter pressure readings at different power levels and different flow readings?

I suspect that the filter pressure is going up causing more restriction and causing the flow to decrease.

I did take some readings, but it doesn't help with nothing to compare to. Tomorrow I will try to collect more precise PSI readings to see if the PSI rises over the course of an hour, thereby reducing the GPM. And then at some point in the next week I will clean the filter and see if that changed the PSI for the various RPMs.

But what about the pump starting at different GPM/wattage and ending up at different GPMs? I would expect if the filter was clogged, the GPM would always end up at the same rate.

 

[JamesW]

I would expect if the filter was clogged, the GPM would always end up at the same rate.

Not necessarily, it depends on how dirty the filter is.

I suspect that it is pretty bad.

What readings do you have?

 

[TaylorN]

Not necessarily, it depends on how dirty the filter is.

I suspect that it is pretty bad.

What readings do you have?

2850rpm=933w=21psi=30gpm 1:00pm

2150rpm=376w=12psi=18gpm 2:41pm
2150rpm=367w=12psi=14gpm 3:03pm

1200rpm=73w=3.8psi=4gpm

Looking back on my other records from this afternoon, I didn't notice the PSI rise at all for a particular RPM over time (maybe 0.5PSI if at all).

I will take new numbers tomorrow to double check since I wasn't focused on PSI today.

 

[JamesW]

Those numbers are way too high.

Definitely time to take the filter apart and give it a good cleaning.

Take some picture of the cartridges before cleaning so we can see what they look like.

 

[JamesW]

You might also have an issue downstream from the filter.

Check the salt cell for scaling or debris.

 

[generessler]

Watts and flow decreasing for a set RPM say that the pump is doing less and less work.

Here's a theory... Clogging around the impeller would be more-or-less consistent with what you're seeing. The clog causes less water to be moved, which is less work, so less watts. (If it were clogged perfectly to a solid disk, the work would be about zero.) When the pump is off, the clog material floats free only to be drawn in again next at the next power up.

I'd try powering everything down; remove the basket; check for junk that got past it into impeller intake area. That's a pretty quick and easy thing to try. Of course you could disassemble the pump to check the impeller.

The only other things that make sense are real oddballs. Impeller slipping on the shaft could do it. Or control circuits broken so that RPM is not actually being maintained. One way you can check that is record the motor before and after the power decrease in order to compare pitches. You'll need a good ear.

 

[ajw22]

Here's a theory... Clogging around the impeller would be more-or-less consistent with what you're seeing. The clog causes less water to be moved, which is less work, so less watts. (If it were clogged perfectly to a solid disk, the work would be about zero.) When the pump is off, the clog material floats free only to be drawn in again next at the next power up.

@JamesW is on the right track with a dirty filter.

Your theory is correct but apply it to the filter.

What is happening is every time the pump is turned off to adjust it the water in the filter drops and the dirt coating the filter slumps down. When the pump is then started there are uncoated areas of the filter that were cleared due to the slumping of the dirt. As the pump runs the filter gets coated with the dirt and the flow slows, RPM decreases along with watts. And the filter clogs again.

This cycle repeats every time the pump is stopped. Performance looks good until the filter reaches its steady state of dirtyness.

 

[proavia]

@JamesW and @ajw22 are spot on in what they said.

Might be time to clean the filter so you know the base PSI at a given RPM. That RPM should be the fastest you will run the pump - not necessarily 3450rpm. High 2000 rpms will do.

I believe running the pump below about 1000 rpm has diminished efficiency. If the SWG works consistently at 1000 to 1200 rpm, there is no reason to run the pump any higher to produce chlorine. Run it higher for a reason - make the cleaner run efficiently, run a water feature for a short time, etc. Actually, it's more correct to state - to produce chlorine and adequately skim the pool surface.....

If you are the least bit handy with PVC, consider installing a heater bypass like the diagram in the link I posted previously. One 2-way Jandy valve and one Jandy check valve, some pipe, a few fittings and some glue.

Your CSI is within the parameters mentioned. Using the non-subscription PoolMath will still show CSI, but as you know will only allow one full set of test results. So if you aren't going to subscribe, write it all down in an easy to read format. Also keep track of the SWG percentage during different times of the year will make it easier to set it next year when the weather conditions are roughly the same.
Continue to lower the ph to 7.2 - this will help lower the TA. Once you get the TA in the 60-70 range, you can let the pH drift up to keep CSI in range. TA, pH, CH and water temp are the main items that affect CSI.

Test your tap water/fill water for pH, TA and CH. Knowing this will allow you to know what fill water factors will play into keeping the pool well balanced.

 

[TaylorN]

Those numbers are way too high.

Definitely time to take the filter apart and give it a good cleaning.

Take some picture of the cartridges before cleaning so we can see what they look like.

Will do! Thanks!

 

[TaylorN]

You might also have an issue downstream from the filter.

Check the salt cell for scaling

I cleaned the cell last week. It wasn't bad at all, but now it is pristine. Maybe the heater isn't flowing correctly in the manifold where the input/output pipes are. For the first 10mins or so it always sounds like there is air in there, but eventually goes away. I wonder if that corresponds with the gpm/wattage. Only way to find out would be to by pass the heater completely, but don't know if I will have time to do that in the shortterm.

Watts and flow decreasing for a set RPM say that the pump is doing less and less work.

Here's a theory... Clogging around the impeller would be more-or-less consistent with what you're seeing. The clog causes less water to be moved, which is less work, so less watts. (If it were clogged perfectly to a solid disk, the work would be about zero.) When the pump is off, the clog material floats free only to be drawn in again next at the next power up.

I'd try powering everything down; remove the basket; check for junk that got past it into impeller intake area. That's a pretty quick and easy thing to try. Of course you could disassemble the pump to check the impeller.

The only other things that make sense are real oddballs. Impeller slipping on the shaft could do it. Or control circuits broken so that RPM is not actually being maintained. One way you can check that is record the motor before and after the power decrease in order to compare pitches. You'll need a good ear.

Thanks! I will definitely reach in there. Recording is not a bad idea. It's easier to visualize and filter certain frequencies versus by ear

 

[TaylorN]

@JamesW is on the right track with a dirty filter.

Your theory is correct but apply it to the filter.

What is happening is every time the pump is turned off to adjust it the water in the filter drops and the dirt coating the filter slumps down. When the pump is then started there are uncoated areas of the filter that were cleared due to the slumping of the dirt. As the pump runs the filter gets coated with the dirt and the flow slows, RPM decreases along with watts. And the filter clogs again.

This cycle repeats every time the pump is stopped. Performance looks good until the filter reaches its steady state of dirtyness.

Right on. That all makes complete sense. Time for a cleaning

 

[TaylorN]

@JamesW and @ajw22 are spot on in what they said.

Might be time to clean the filter so you know the base PSI at a given RPM. That RPM should be the fastest you will run the pump - not necessarily 3450rpm. High 2000 rpms will do.

I believe running the pump below about 1000 rpm has diminished efficiency. If the SWG works consistently at 1000 to 1200 rpm, there is no reason to run the pump any higher to produce chlorine. Run it higher for a reason - make the cleaner run efficiently, run a water feature for a short time, etc. Actually, it's more correct to state - to produce chlorine and adequately skim the pool surface.....

If you are the least bit handy with PVC, consider installing a heater bypass like the diagram in the link I posted previously. One 2-way Jandy valve and one Jandy check valve, some pipe, a few fittings and some glue.

Your CSI is within the parameters mentioned. Using the non-subscription PoolMath will still show CSI, but as you know will only allow one full set of test results. So if you aren't going to subscribe, write it all down in an easy to read format. Also keep track of the SWG percentage during different times of the year will make it easier to set it next year when the weather conditions are roughly the same.
Continue to lower the ph to 7.2 - this will help lower the TA. Once you get the TA in the 60-70 range, you can let the pH drift up to keep CSI in range. TA, pH, CH and water temp are the main items that affect CSI.

Test your tap water/fill water for pH, TA and CH. Knowing this will allow you to know what fill water factors will play into keeping the pool well balanced.

Thanks!

The "high" for getting the pool cleaner moving at the correct speed is 2850rpm with the 3 way valve adjusted accordingly, so I will definitely track the psi for that. But heck, I will also track a handful of rpms from 1200-2850 just to have the data for the future. I was just recently trying to see if the scaling in the swcg would stop developing if running at higher rpm, but would love to eventually run at low speeds to of course to save electricity

I'll definitely look into a heater bypass. I'm slow with PVC work, but can get it done. And I'd prefer the automated bypass, so I'll see if that will play nicely with my existing jandy controller.

I have been tracking the swcg % and rpm for a few years now, and have gotten lucky with chemistry so there hasn't been much scale until the last year. Maybe it's finally building up too much CH and the CSI has been creeping positive. The tap water is 250-300 CH, so much better than 500 CH currently in the pool, but replacing half the water would definitely cost at least $500 out here.

Sounds like if I can keep the pH around 7.2 consistently and get the TA lower, the CSI might end up in a manageable range.

Thanks for all the advice. I'll definitely keep you all post!

 

[TaylorN]

I forgot to update this thread. On 9/13/2022 I cleaned the filter. It didn't look too bad, but after spraying down there was a lot of material jammed in it.

Seems to be what was causing the wattage/gpm (gallon per minute) decrease over 30minutes. Now with a clean'ish filter, the flow wattage/gpm is rock stable and the gpm almost doubled at every RPM/Wattage. What's interesting is that the PSI didn't change (lower) dramatically. I guess I'll use GPM for the baseline for cleaning the filter.

Before Cleaning

2850rpm	980watts	22psi	34gpm
2200rpm	428watts	13.5psi	24gpm
1800rpm	227watts	9psi	13gpm
1600rpm	170watts	7psi	10gpm
1400rpm	113watts	5psi	8gpm

After Cleaning

2850rpm	1174watts	27psi	58gpm
2200rpm	523watts	11psi	42gpm
2150rpm	488watts	10.5psi	39gpm
2100rpm	478watts	10psi	40gpm
1650rpm	212watts	7psi	22gpm
1600rpm	190watts	6.5psi	19gpm

Oh and the scaling seems to not be building up as quickly. I assume during SOLAR operation, the GPMs were not enough to get to the 20gpm manufacturer recommendation, and the water was really hot so it was affecting the overall CSI. Same with when the Gas heater was on for the spa. That was supposed to be a minimum of 40gpm and was more like 20gpm before.

I know have the low pool setting at 1650rpm/22gpm, Heater at 2600rpm/44gpm, and Solar at 1850rpm/20gpm

Thanks for all the support! I really appreciate it!