Variable Speed Questions

[DThompson55]

Can someone explain how a variable speed motor will save money? The Pentair site, if it can be believed, says I'll save, in my case, over 75% on the cost electricity. Is it just a more efficient motor? Does it not have to run as many hours? Does it run the same number of hours but at a lower speed? It still needs to move the same amount of water so I don't understand how it can run slower. And then how does it know what speed it needs to run at? Too many questions. I know. There's probably a TFP post pinned somewhere that explains this, or this has been asked and answered 100 times. Sorry for that.

 

[BK MAC]

Can someone explain how a variable speed motor will save money? The Pentair site, if it can be believed, says I'll save, in my case, over 75% on the cost electricity. Is it just a more efficient motor? Does it not have to run as many hours? Does it run the same number of hours but at a lower speed? It still needs to move the same amount of water so I don't understand how it can run slower. And then how does it know what speed it needs to run at? Too many questions. I know. There's probably a TFP post pinned somewhere that explains this, or this has been asked and answered 100 times. Sorry for that.

Good video running the variable speed pump through different settings while showing corresponding flow rates and power consumption.

 

[Jimrahbe]

55,

VS pumps use special motors that are not at all like the old electric motors used on most pool pumps. With a single speed pump, it runs at full speed all the time.. VS speed pumps use about the same electricity when running full speed as a single speed pump.. The key is that you can run the pump at low speeds, yet still move a lot of water.

I can run my 3 HP IntelliFlo 24/7, most of the time at only 1200 RPM for less than $20 bucks a month.. I don't have to run it 24/7, it is just something that I like to do so that my salt system generates a little chlorine all the time, and I also can skim all the time.

One great thing about a VS pump is how quiet it is.. At 1200 RPM, you almost have to touch the pump just to make sure it is running.

Why do you think you have to run your pump for a set amount of time? We have many members that only run there pumps for 3 or 4 hours day..

The main advantage to VS pumps is that you can run the best speed for the specific task you want to do.. You can run it fast when using the spa, another speed for a waterfall, and yet another speed when in the Pool mode.

VS pumps have an internal timer so you can set the schedule you want it to run.

Thanks,

Jim R.

 

[DThompson55]

Thanks @Jimrahbe - I know next to nothing about pools, but if i'm pushing 36 GPM with my one speed motor today I'll be pushing something less than that with a lower speed variable motor and so I'll have to run the pump longer to circulate the same amount of water, right? I guess the savings might come in because it should take one quarter of the energy to run half the GPM rate, even though then I'll need to run twice as long? (there's some exponential math at work here that I gathered from the above video someone posted, but i'm probably wrong)

As for why I think I have to run my pump for a set amount of time? Again, I know next to nothing about pools.

 

[markayash]

The biggest advantage is like Jim said, you don't need 18 psi of filter pressure, I run mine at 2100 rpm and 4psi 24x7. I have a spa and water fall or would turn it down more
My over all power bill before and after dropped around 25%

 

[DThompson55]

Thanks @markayash - it sounds like running the filter at the lowest possible setting that still circulates once a day would save a lot of money. I think that's what you're saying. Sounds like I can get away with about 10 GPM over 24 hours, and then i'd be taking advantage of night power rates too for a good part of that. Is there any downside?

I don't know what PSI does. All I know is that when it goes up by 10 it's time to clean the filter. But it's got to be related to flow somehow. So maybe it doesn't matter. Again, I know nothing about pools.

 

[markayash]

If your debating it I would say go for it..With my old pump I would turn the pump off when company came..Now I have to walk over sometimes and verify it's running
I leave my main drain off and just run it on low 24x7. They are so much more efficient you won't really have to run it at night unless you want to.

 

[Jimrahbe]

55,

It sounds like you believe in the old turn-over myth.. It was on old rule of thumb not based on any science... Chemicals keep your pool clear and sanitized, not the number of times you run your water through the filter.. The filter is only there to capture what falls into the pool.. It is not there to prevent algae..

You could run a VS pump at a low RPM the same number of hours you do now, or less, and your pool will still be just fine.

How many hours a day do you currently run your single speed pump??

All of us did not know anything about pools before we found TFP.. You are right at home..

The downside to a VS pump is the initial cost... another good option is a 2-speed pump... which still saves on the electrical bill.

Thanks,

Jim R.

 

[DThompson55]

@Jimrahbe - Thanks, I don't know if I believe in a turnover myth. I mean who knows anything? The filter probably runs maybe 5 or 6 hours a day right now. It's on a timer. This is very confusing. But I'm fairly well convinced that a variable pump will solve a problem I don't know if I have. So I think I'm done for now. Thanks for your helps.

 

[Homebrewale]

Look up Pump Affinity Law.

 

[Oly]

More speeds more options with quiet running and low pressure are good things.

 

[DThompson55]

Thank you @Oly and @Homebrewale - I vaguely understand pump affinity law. I took a semester of fluid engineering at one point. Power is related to the cube of the shaft speed. Ok. But then if running quiet and at low pressure are the objectives there's an easy way to optimize for that. Take out the pump all together. Seriously, how much flow do I need to have a trouble free pool? Nobody can answer that. That's why I think it these things, while great for some people, solve a problem I don't know if I have.

 

[JJ_Tex]

Seriously, how much flow do I need to have a trouble free pool? Nobody can answer that. That's why I think it these things, while great for some people, solve a problem I don't know if I have.

You seem to be looking for a magic number for flow or runtime and it doesnt exist. You run the pump for a couple of reasons:

• Mix Chemicals
• Make chlorine with your SWCG, or use your chlorine tab feeder (not recommended for every day use)
• Skim stuff off the top
• Run water through your filter

Usually the long pole in the tent per se is skimming and making chlorine if you have a SWCG. The mixing of chemicals and running water through your filter have a much less requirement time wise.

I'm assuming your 5 hours a day is working for you. If you had a VS pump, you likely could get the same results with say 8 hours on a low speed for much less electricity usage and the advantage of 3 more hours of skimming. There is an article pasted below if you want more info on it.

I may have missed it, but is your pump working fine? I personally am not sure I would ditch a perfectly good pump that is working for you, but if you need to replace it I would look at a VS or 2 speed pump. They cost more up front, but give you the flexibility to save $ monthly and pay for themselves many times over.

Determine Pump Run Time

To figure out how many hours you need to run your pump, you need to know how fast your pump works. You can find this here.

www.troublefreepool.com

 

[Oly]

easy way to optimize for that. Take out the pump all together. Seriously, how much flow do I need to have a trouble free pool? Nobody can answer that. That's why I think it these things, while great for some people, solve a problem I don't know if I have.

Turn your pump off for a week and let us know how that works out for you.
Correct, nobody can answer that question and this is where empirical evidence shines. The more options you have the better chance you have of finding the answer and given the changing nature of pool care throughout the seasons you will find your answer changes. So yes more options, more better.
JJ_Tex has a good question, have you clearly identified you problem yet?

 

[DThompson55]

Thanks @JJ_Tex - That's a well thought out article. I always thought the filter had something to do with removing algae. One more thing I'm wrong about regarding pools. The pump seems to run just fine for about 5 hours a day. It's just how the timer is set. I probably saw it recommended on some website. Never changed it. (Except when we slam, and then it runs continually). Our season is about 100 days, or just a tad over. So it runs about 500 hours total, maybe. Half that again for slamming, so 750. If I compare next month's electricity bill to August's that should give pretty good indication of what it costs per season, and from that I start to look at what a lower speed pump might save. I just don't want to have to go out and constantly tweak the speed of the thing based on some conditions I don't understand. Set it and forget it.