Very Low GPM with DE filter & Automatic Cleaner

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stever

stever

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LifeTime Supporter
Nov 25, 2007
285
Escondido, CA (near San Diego)
Hello all, I'm new here,

I am getting ready to start on our in-ground pool (about 20,000 gal) with spa and have been trying to do everything possible to minimize electriciry usage as we live in southern California (enough said). Also, the quiteter the better.

With that in mind, I am looking at either the Intelliflo VS (set the RMP) or VF (set the GPM) and want to run long cycles (24 hours?) at very low GPM.

The rest of the system is:
- Pentair 60 sf DE filter (with separation tank)
- Pentair 400,000 BTU heater
- Solar (might end up being stubber in for future if too much $$$)
- Pentair Intellichlor IC40

I have read that the power used drops dramatically if the pump is run slower, but am concerned with the low GPM. What is the minimum recommended GPM for a DE filter, automatic cleaner and solar?

I like the DE filter as it filters better, but the cartridge filter may work at a lower pressure...

I'm sure I fogot to mention something.... but tried to get the needed information out to you.

Thank you for your ideas!

Steve
 
Welcome to TFP!

Here are a couple of things to keep in mind. The IntelliFlo VF can't be set to a flow rate much lower than 15 GPM in flow mode. It can be run at lower flow rates by setting a speed, but the flow meter in the pump won't read much lower than 15 GPM. DE filters need a reasonable flow rate to coat the grids but should then continue working at lower flow rates. Both pressure and suction side automatic cleaners are going to require significant flow rates when they are running and many of them require a separate booster pump (which will still require that the main pump be running at a reasonable flow rate). Solar systems require some minimum pressure, depending on how high up the panels are. Depending on the height, that may or may not be a significant flow rate. Solar systems also require 3 or 4 GPM per panel, which may or may not be significant depending on the number of panels.

Running the pump more slowly for longer will generally save money, but other considerations usually limit how slow you can go.
 
JasonLion said:
Welcome to TFP!

Here are a couple of things to keep in mind. The IntelliFlo VF can't be set to a flow rate much lower than 15 GPM in flow mode. It can be run at lower flow rates by setting a speed, but the flow meter in the pump won't read much lower than 15 GPM. DE filters need a reasonable flow rate to coat the grids but should then continue working at lower flow rates. Both pressure and suction side automatic cleaners are going to require significant flow rates when they are running and many of them require a separate booster pump (which will still require that the main pump be running at a reasonable flow rate). Solar systems require some minimum pressure, depending on how high up the panels are. Depending on the height, that may or may not be a significant flow rate. Solar systems also require 3 or 4 GPM per panel, which may or may not be significant depending on the number of panels.

Running the pump more slowly for longer will generally save money, but other considerations usually limit how slow you can go.
Click to expand...


Thank you for the response. A lot of thie information is difficult to find even after reading the downloaded owner's manuals. The 15 GPM limit is good to know, and assuming the sensor is accurate at this lower limit will achieve about 1 turn/day at 24 hours -- I wouldn't want to go any slower (or less GPM) for this pool. In the winter I might cut the time some.

I like the VF because it adjusts for filter pressure and solar priming. I don't like the price much (+$600 over VS).

Will the 24/7 run of the pump be bad for it as it does not give it time to cool down, or (like a computer) add to its life by not putting it through multiple cool/hot cycles?

The Intellichlor (oversized a bit at IC40). is rated for 10,000 hours. At reduced flows is this extended or does it remain 10,000 hours. I don't want to extend my runs to save electricity only to have to replace the cell at just over a year.

You are right -- the cleaner will have to have a higher GPM. I'll have to program the pump to increase GPM for 4 hours or so a day. I guess that will be about 4 hr@50GPM + 8 hr@15GPM -- I'll have to see how it works. Do you know what the most efficient heat transfer is for solar (GPM?).

Is 15GPM 24/7 recommended or am I making this more complicated than needed for no real benefit? Are there any drawbacks?

Thanks!
 
All of the pumps you might be interested in are designed for continuous usage. You can run the pump 24/7 and it will be fine.

The Intellichlor cell is rated for 10,000 hours with the cell on. The total time the cell is on will be the same regardless of what your pump run time is. The control unit cycles the cell on and off based on the percentage setting, which you will need to adjust for a specific FC level in either case which will result in the same on time in either case (but different percentages). Oh, the Intellichlor has a minimum flow rate of 15 GPM also.

Not all solar panels are the same, but most of them are designed for 3 to 8 GPM per panel. At the low end of that range they are less efficient and at the high end of that range they don't last as long. Low flow rates are inefficient and high flow rates require higher pressures which stress the panels. 4-6 GPM is usually a good compromise, but you should check the specs on the specific panels you will be getting.

Most people/pool builders don't bother with this level of optimization. As electric rates go up paying this level of attention becomes more important, but so far it hasn't caught on. The only disadvantage of low flow rates I have heard of is that skimmers often don't work as well at low flow rates. This will vary somewhat depending on your pool design, some people don't have any problems and others need to turn the speed up for a little while each day to get the skimmers to catch the debris they seem to miss otherwise.
 
Just a couple of things to add to what Jason has covered.

Running the Intelliflo at it's lowest setting or flow rate may not be the most efficient use of the pump. The best efficiency metric for a pool pump is GPM/kw. Based upon the energy curve for the Intelliflo, the peak GPM/kw occurs around 900 RPM and depending on your plumbing system will deliver 20-40 GPM. Targeting this range will give you the lowest total energy use by minimizing turnover rate and energy consumption.

Also, one of the benefits of putting solar panels on your roof is that they will run at lower pressure than they would at ground level. This means running at higher flow rates won't necessarily create too high of a pressure at the panel.

Given the equipment you have and the properties of an Intelliflo pump, you may want to reconsider running the pump at such a low flow rate.
 
The constant flow rate feature makes a difference. Since how dirty the filter is affects the flow, a constant speed will either waste electricity when the filter is clean or have insufficient flow when the filter is dirty. It is much more difficult to say what that difference is worth. If you somehow manage to turn the variable speed version to the ideal fixed speed it will take quite a while before you save $600 in electricity, even in California.

On the other hand, figuring out the ideal speed is not so simple. Many people set it too high because they lack any obvious way to figure out what the ideal speed is. That kind of error could add up to $600 in a reasonable amount of time given the high electric rates in California.

One other thing to keep in mind is that more complex pumps have more things that can go wrong. A simple single speed pump tends to "just work" more often than not. The IntelliFlo has had a slightly above average rate of problems, partly because there are so many settings and it isn't always obvious what some combinations of settings should actually do.
 
stever,

As a retired engineer, I enjoy technology and whiz-band features as much as anybody, but I am leery of the "constant flow" IntelliFlo model. The "constant flow" feature will essentially mask how dirty your filter is. I WANT to see the pressure rise and flowrate decrease as the filter gets dirty, and the "constant speed" IntelliFlo model will do this for you.

There were many times on the job where an automated sytem, due to its ability to change flowrate, hid a festering problem up until the automated system hit its limit to adjust flow. And by the time that happened, the underlying problem had usually gotten much worse than it otherwise would have been.

I have the same problem with automated pool fill systems. If there is some sort of leak, you will never know since the pool fill system keeps the pool full. The only way I would have an automated pool fill system is if the system also kept track of how many gallons the pool fill system was using daily (or weekly).

On second thought, I think the "constant flow" IntelliFlo could work, but you would want to have some sort of differential pressure gauge at the filter. A differential pressure gauge would measure the difference in pressure between the input side of the filter and the output side of the filter. This way you would have the information neceessary to know when the filter needed cleaning.

Titanium
 
The IntelliFlow in its normal Filter mode (i.e. without special "features" turned on such as waterfalls or solar heating) will sense the pressure on the output side (probably calculated from the RPM needed to maintain a flow rate) and when it goes up above a reset "clean" pressure value, then it sets an alarm telling you to clean the filter. You can set the PSI rise that you want to indicate when the filter should be cleaned. When you next backwash (or clean) the filter, you run a backwash cycle in the pump (even if it doesn't really backwash, as with a cartridge filter) and that resets the PSI so it can measure a new rise from that point.

I don't use that feature because I have a cartridge filter that barely registers a rise in pressure and I only have to clean it once a year (it's an oversized filter plus I've got an electric pool cover that keeps the pool pretty clean).

Richard
 

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Titanium,

Actually, the constant flow will make the filter PSI rise faster than normal. In a fixed speed pump, the flow rates decrease with a dirty filter (i.e. higher head loss) but with the Intelliflo, the flow rate stays constant thereby creating higher head loss and higher filter pressure than the fixed speed pump.
 
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