Optimal flow rates for variable speed pumps

[Gary77375]

I have an Intelliflo VF variable speed pump controlled through a Jandy Aqualink. I can program the Aqualink to control the flow of the pump depending on what other devices are in use. I am trying to figure out the optimal settings and was hoping to get some opinions from others who have experience with variable speed pumps. Our pool is about 28,000 gallons with the spa, has 1 just 1 skimmer, but 3 drains in the main pool. The main pump is a Pentair Intelliflo VF and has a Hayward H400IDL heater, a Pentair CCP520 cartridge filter, a Jandy PCL1400 chlorine generator, a Polaris 3900 on a booster pump, and a waterfall on its own pump. I want to program the pump for optimal GPM for the devices while being as energy efficient as possible. I've done a few hours of searching and I'm having a hard time finding optimal flow rates for these devices.

How many turns-per-day do I want for a 28,000 gallon pool? About 1.0 / day?
The electricity usage seems much more efficient at lower GPM, so is it advised to run the pump 24/7 at a low flow rate calculated for my turns per day to get the most efficient energy usage, or will running the pump slower for longer be bad for the pump? Or should it be higher for a period of time to make the skimmer more efficient?
What is the optimal / recommended GPM for a 400,000 BTU heater?
What is the recommended GPM on the main filter pump while the Polaris 3900 is running with a single-speed booster pump?
Since the waterfall has its own pump, do I need to worry about the GPM on the main pump?
Does the efficiency of the chlorine generator depend on the GPM?
What is the recommended GPM for the spa when the pool is in spa mode?
Anything else I should consider when programming the flow rates for the devices?

Any comments or opinions or links to articles on this topic are appreciated!

 

[shakenbake]

Lots of great questions! I wish I was wise enough to answer all of them. I've suffered though the experience of being a hard headed engineer not listening to my PB and others, and learning the hard way a few times.

I turn my 38K gallon pool over about once a day through a 72sqft DE filter and a 200W UV light. I run my SVRS pump at 1500RPM, which is about 30GPM and 300w in my system (pretty significant head, as the pump is about 3 feet above the water). Running the system wide open is 2500W and 80GPM, or about 3x the power for 1 turn. I've had trouble keeping automatic chemical systems working at that low speed. PB gave up and offered a floater. My target FC is about 1.5 with the UV light. To the credit of the UV system, the pool has been way lower on the FC side of things and I've never had any issues even with 10 kids in the pool, leaves, pollen and lots of other spring-time stuff. The LQ and Rainbow were not able to manage it at the low flow rates, so I've switched to a chemical injection system with dedicated pumps. The automatic systems are also difficult to control if you are changing the filter-pump speed a lot since they are powered by water flow. I guess I could dump chemicals in like very other pool owner...but that's boring

Don't worry about the pump, it's designed to run at any speed continuously at high loads.

I skimped on the flow rate through my heat pump and killed it. It's installed in parallel with my gas heater and 40GPM through both was not enough, even though the heatpump has a flow rate switch. The gas heater seems to be able to handle the higher water temps at lower flow rates, but I've had to install an actuated bypass for the heatpump so that it gets all the flow when it's on - 40GPM is plenty.

I recommend that you get a flow meter (for those without the VF pump). Install it after the filter so that it does not get clogged up with debris.

 

[JasonLion]

One turn per day is a good starting place. Most pools need a little less than that, but start there.

The IntelliFlo is most efficient around 1,000 RPM, which usually works out to less than 24 hours a day operation.

You may need to adjust the RPM up to keep your skimmer(s) working well. There is no way to know if that is true without trying it out at 1,000 RPM and seeing how the skimmer does.

A large heater will need a higher flow rate when it is on, often something around 40 GPM, check your heater manual for the minimum flow rate. Depending on pump model, you can either program the flow rate for the heater, or you need to work backwards to guess at an appropriate RPM.

Booster pumps only need a low flow rate on the main pump and they take care of the rest. No need to bump up pump speed for the booster pump.

If the waterfall is on it's own pump, the main pump doesn't care if you are using the waterfall or not.

The SWG needs a minimum flow rate to work, often around 15 to 25 GPM, depending on brand. Usually you will get enough flow at 1,000 RPM, but occasionally you need to bump up the flow rate to keep the SWG happy.

The proper speed for the spa is difficult to predict, as it depends very much on details of your plumbing design. Experiment with it, starting around 2,000 RPM and see how things go.

Trial and error is your best guide. Every pool is a little different, so we can't give you exact numbers.

 

[Puffin]

You may need to adjust the RPM up to keep your skimmer(s) working well. There is no way to know if that is true without trying it out at 1,000 RPM and seeing how the skimmer does.

Jason, what do you mean (I'm sorry, I'm still really new to this)? how do I know they are working properly? Is it just how much stuff is getting caught by the skimmer(s) vs. how much falls to the floor?

 

[SWpisces]

Thanks for posting these questions and answers!( Being a new pool owner too I"m learning the basics of skimmers/rpm's/gpm/s,etc.) Love the variable pump but am trying to learn all the nuances and sweet spot for it as well! So grateful for the shared knowledge here!
I will be following the answers on above questions.
One question I have is: Do those with a variable pump run their dedicated line cleaner the entire time the pump is on? We have an automated safety cover so we don't get tons of dirt. Our PB, at his pool school, was setting the cleaner to run the entire time...mind you, he doesn't use variable speed pumps much--- and we have set our pump to run for 16 hours@ 1200 rpm's--new pool/plaster, etc. We just have a mechanical timer and have the VS 3050 pump that has only the rpm's setting.
We've decided to just use the cleaner when it's necessary and not leave it in all the time. After experimenting we have found we need to put the speed up to the 3rd speed (2350 rpm's) to get the Polaris ATV to run properly. Is anyone else using this type of cleaner? I believe now we should have had a cleaner that operates better with low flow.

 

[susa]

Found out that Poolvergnuegen 2x runs just fine @ 1200 rpm and I leave it in pool for several days.

Two 5 hr programs, one higher speed and low speed (keeps IC40 cell off) and on 3 days a week I run ultralow 24 hrs at below 900 rpm

On the last setting cleaner is very slow but still runs

 

[JasonLion]

Jason, what do you mean (I'm sorry, I'm still really new to this)? how do I know they are working properly? Is it just how much stuff is getting caught by the skimmer(s) vs. how much falls to the floor?

Yep, at too low of a flow rate, the water doesn't circle around the pool any more and surface debris stops getting drawn into the skimmer. The speed where this starts to be a problem varies quite a bit from pool to pool.

 

[SWpisces]

Thanks Susa....I'm assuming with your change in speeds you have your variable speed pump connected to a digital timer/programmer?

 

[Gary77375]

Thanks for the great information! I do have a few follow up questions.

I was able to find the minimum GPM for most of my pool equipment, but not the "optimal" flow rates. For example, the heater manual says minimum flow of 40 GPM, so does that mean I should run the pump at 40 GPM when the heater is on? Thinking about how a heater works as an engineer, it seems that the heater would heat the pool / spa more efficiently at a higher GPM. But I don't know if there is a calculation or guideline to follow for the flow rate of a heater.

Since the waterfall is on it's own pump, does that mean that the main pump does not need to be on "at all" when the waterfall is running? Or are you just saying that the main pump should be on, but the GPM does not matter?

The manual for the SWG says it should have a minimum of 30 GPM to work. It is a Jandy PCL1400 that has a flow rate sensor and the manual says that it will automatically shut off if does not detect enough flow. When I set our IntelliFlo pump to 20 GPM, the pump says it is operating at 1370 RPM and 215 watts, which seems to be about the most energy efficient setting. The SWG has a code for "low flow", and even though the manual says it should have at least 30 GPM, it runs without any warnings or errors at 20 GPM. Since the SWG recommends at least 30 GPM and my system does not have a way to control when the SWG is on or off, does that mean I should always run the pump at a minimum of 30 GPM (which runs at 561 watts vs 215 watts at 20 GPM)? Or is it more of a function to make sure the pool is getting enough chlorine and it is safe to try it to see if it generates enough chlorine at 20 GPM?

Thanks!

 

[JasonLion]

The heater is more efficient at higher flow rates, up to about 80 GPM, but the difference isn't all that large and the pump is less efficient at those flow rates so it kind of cancels out. I would use 45 or 50 GPM for the heater, just to make sure you aren't right near the lower limit.

Assuming the waterfall is plumbed the way most of them are, which the waterfall pump having it's own separate suction, then the main pool pump doesn't need to be on at all while the waterfall is running.

I'm less sure about the SWG flow rate. That is the highest minimum flow rate I've see for a residential SWG cell. It is not clear to me why they are asking for that flow rate. There are some possible reasons that are fairly important, or they might just be overly cautious.