Standard vs. Variable speed pump

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Pentair itself has a good video on it, but basically, this isn't a linear relationship. It doesn't take twice as much power to produce twice as much pumping power. It takes multiples of that so it's more of a geometric curve where the electricity needed at a higher power level increase faster than the power produced by the pump. Thus running a pump longer at lower power takes much less electricity than at a higher power for shorter periods of time.

Plus, I'm sure I've seen some articles that mention that filters work more efficiently if the water is moving through them more slowly.
 
manoweb said:
I understand how a variable speed motor works and how to control one. I also do not consider the iphone the pinnacle or phone technology :D but that is a whole different matter :)
I do not understand the plumbing terminology you mentioned so I will have to read up on those.

However I understand that a pump has a goal to move so much water every day. It can do it in a matter of hours at the maximum speed, or take the whole day at a lower speed... In principle one would think the energy required to move so much water is the same and does not matter how much time it takes, but there is evidently a physical reason why going slower is more efficient. Maybe less friction in the pipes if water goes slow?
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Your understanding is based on a false premise - pools do not need a specific number of turnovers per day. The turnover theory is pushed by PBs a lot but it is basically false. A study in FL showed that people could not visually tell the difference between a pool that was circulated for 2 hours and pools circulated for longer than 2 hours. Chemical distribution and homogenization happens in well under 2 hours, so the notion that you need a specific number of turnovers of the water in a pool is bunk. This is not unlike how some PBs tell owner to take the air temperature and divide it by 10 then round up to the nearest integer and that is the number of hours you should run your pump....total B/S not grounded in anything remotely scientific but spread around as "conventional wisdom".

Also, as others have said, the relationship between pump power, water flow and electrical power is not linear. Read all about it here -

Hydraulics 101 - Have you lost your head?

Just to pull out a quote -

But what do these equations really tell us? For one thing, a reduction in speed has a proportional reduction in flow rate but has a much more significant reduction in the required HP required to generate that flow rate. This is the primary reason a two speed or variable speed pump can save so much energy at lower speeds.

For example, low speed of a two speed pump has about 1/2 the flow rate as high speed and the affinity equations tell us that it requires only 1/8th the power of high speed. Unfortunately, two speed motors lose about half their efficiency at low speed so the energy use is only about 1/4th of high speed but still significant. So even though low speed needs to run twice as long for the same turnover, it will still save over 50% in total energy.

Current generation variable speed pumps provide even more cost savings over their two speed counterparts. Plus, given the range in RPM settings, the pump can be optimized for the given pool plumbing. The flexibility of a variable speed pump ensures a maximum energy factor for nearly any operating condition.

Unlike two speed pumps, variable speed pumps can maintain fairly high efficiency at lower speeds thereby reducing the amount of energy consumed for a given head loss. A 3/4 HP full rated Whisperflo two speed pump has an energy factor of 6.3 gallons/watt-hr at low speed while the Intelliflo pump has an energy factor of over 10.3 gallons/watt-hr for same flow rate so the Intelliflo will save close to 40% more energy than the 2 speed. However, a VS costs more than a two speed pump so the cost difference could be more than the energy savings of the pump. For a small pool and low energy costs, a VS may not make sense and a two speed could end up being more cost effective over the life of the pump.
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Litespeed said:
Pentair itself has a good video on it, but basically, this isn't a linear relationship. It doesn't take twice as much power to produce twice as much pumping power. It takes multiples of that so it's more of a geometric curve where the electricity needed at a higher power level increase faster than the power produced by the pump. Thus running a pump longer at lower power takes much less electricity than at a higher power for shorter periods of time.
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Oh well this is true by definition, otherwise slower pumps would not be saving any energy. But my question is why this relationship is not linear. I have not had time yet to read up about it, that is why I was just thinking to friction or cavitation that increase a lot at higher speeds.

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JoyfulNoise said:
Your understanding is based on a false premise - pools do not need a specific number of turnovers per day.
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Oh! I am sorry, I am getting quotes from Pool Builders as we speak, and... some of them have mentioned that. One was actually proposing a VS pump, and he explained that I have to circulate the whole size of the pool through the filter each day, and I could do it slower to save energy with a variable speed pump. It kind of made sense so I assume it was true.

What is the metric then? It just varies from pool to pool and one has to find out how much recirculation is needed at minimum to keep the pool clean, including seasonal differences? There must be a rule of thumb to calculate how much to pump? Sorry these are probably very silly questions for a seasoned pool owner but I'm just starting!


Also, as others have said, the relationship between pump power, water flow and electrical power is not linear. Read all about it here -

Hydraulics 101 - Have you lost your head?
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I will thanks!
 
I'm not sure there is a metric. I've found you need to run the pump for different reasons depending on what's hooked up to it. Also here the study referred to http://consensus.fsu.edu/FBC/Pool-Efficiency/FAU-FPL-NSPI_1984_study-efficiency_of_circulation_systems.pdf

1) filter the pool (2 hours should keep it clear see paper above)
2) SWG (dependent on size of pool, FC loss on a given day...)
3) Suction cleaner
4) Water features
5) Skim the pool ( I can swim with stuff floating in the pool but others like to see a clear surface) a great reason to have a VSP. I can set it to 1400 rpm on my pool and it skims the pool and my overflow from the spa stays fully covered in water.
 
JoyfulNoise said:
Hydraulics 101 - Have you lost your head?
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What a great resource. I find some concept easy because they are just like signal transmission lines.

I believe the answer to my question is in the introduction paragraph:

The second component of head is dynamic head loss which is due to the friction loss of water inside of pipes, fittings and other equipment. As water travels through a pipe, the friction against the internal structures reduces pressure. A pool's plumbing system will experience dynamic head loss on both the suction side of the pump and return side of the pump since water is moving through pipes on both sides. The faster water moves through a pipe, the more head loss
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Bhebert449 said:
Are there guidelines on how to optimize the pump speed with given demands (filtration, sanitation, etc.). Just trying to prepare if my PB is not up to programming the VS pump should I go that route.
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Each pool is different thus takes experimentation. Can you fill out your signature with your planned pool type, chlorination method, etc. See Pool School - Getting Started

A starting point for your base flow rate is if you have a SWCG. Use the minimum flow rate to close the flow switch to allow the unit to create chlorine. Then, if you need higher flowrates for cleaners, spillovers, skimming, etc, you program individual times for those functions. The SWCG will continue to operate during those times, but they can be imbedded in the automation schedules.

That all assumes you will have automation.
 
Just got the pricing from my PB to upgrade to the VS pump from the Whisper Flo. It is $800. Seems a little steep. Here are the specs of my pool:

36'X17'.5"X16"11" free form, 654 Sq Feet, 114' perimeter 4' - 6' - 4' depth, travertine coping, one sun bench with 2 bubblers, 9' X 6'5" freeform attached spa raised 18" with 11' stacked stone spillway, Intellichlor IC 40 salt, cellDolphin DX3 robotic cleaner, Pentair CP420 cartridge filter,400,000 master temp heater Easy touch with screen logic automation
 
I would suspect the retail number is about $500 extra for the VS vs Single Speed - so his markup adds the extra.

Still worth it in the grand scheme of things -- but your call.

Take care.
 

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I didn't know a thing about pool before I built and I still have plenty to learn but my builder wanted to use a 2 speed pump and I said I wanted a variable. he said it was an upcharge but I wanted it for the fact of being able to run the pump at a very very low speed 24/7 like others do here so my salt can be evenly converted to chlorine throughout the day so my levels stayed more consistent. I made sense in my head that if I run it longer but way slower I will save money and also but less strain on my sat system to also hopefully save it's life a bit more to save money also.

I forgot my upcharge for the pump. I said ok and then I aid I wanted salt also cause it wasn't in there and he ended up giving me the salt cell with no extra charge.

but man I know from using it for a few months now you can run that 3 hp Pentair at 1200-1500 rpm for noting 24/7.

jim
 
I have a direct side-by-side comparison as I have an IntelliFlo for the pool and a 3HP WhisperFlo for my waterfall (the wet ends are exactly the same so they are hydraulically equivalent). I run my pool’s circulation system 8-10 hrs per day with various speed cycles set (SWG runs inside the overall schedule for 4-6 hrs per day). I also run my waterfall for 1 hr per day broken up into two 15min blocks and one 30min block.

My WhisperFlo pump uses as much energy in that one hour of run time that my entire schedule of run times that my IntelliFlo uses. In short, single speed pumps are energy hogs and most pools can be run quite efficiently at lower energy usage.
 
B,

As Matt points out... the SuperFlo is also a VS pump, but it cannot be controlled by the EasyTouch.. You need to make sure NOT to get the SuperFlo VS..

And as Marty points out... Do NOT get the IntelliFlo with the SVRS option.. I have that pump and can guarantee it is not the one you want...

Jim R.
 
I think that's the older version of the IntelliFlo and not the IntelliFlo 2-VST . You might want to check with Pentair directly as they can give you Model Numbers for the exact pump you want. I believe the one you were quoted does not have the rotatable display.
 
B,

Model # 011018 does not have the rotatable screen, but since you will have the EasyTouch and ScreenLogic, you won't be using the pump's control panel but a couple of times a year, if at all.

It is an excellent pump and I think a better valve for the buck in your case..

Glad you were able to get you Pool Builder to come around to your view point.

Thanks,

Jim R.
 

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