Best speed and run time for a variable speed pump

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Hayward Pool

Hayward Pool

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Oct 15, 2014
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Split off of this topic. JasonLion

Hi Jason, we have found that running the pump at the lowest possible speed for 23 hours to be the best for circulation. You can program it (not sure if you are using the standalone interface on the back of the pump or through a controller) to kick to higher speeds on a timed basis for cleaners or solar. The 4 speed buttons can be used for heater operation or spa jets if you have a spa.

John the Hayward Tech
[email protected]
 
Re: Hayward Tri-Star Variable Speed

John,

The pump run time study in my signature is the only scientific study I have seen so far that clearly shows running a pump more than 3-4 hours is just a waste of energy. Also, there are many people on this forum which have greatly reduced their run time to these levels without ANY reduction in water quality including myself. So if you have a another study that shows otherwise, please share the data and/or report. If not, what evidence do you have that shows there is any difference with run time?
 
Re: Hayward Tri-Star Variable Speed

Hayward Pool said:
running the pump at the lowest possible speed for 23 hours to be the best for circulation
Click to expand...
In a technical sense, you are probably right. But it hardly matters. Far less circulation is perfectly fine in nearly all cases. There are a number of criteria to balance out. Circulation is just one issue among many, and not usually one of the more important ones.

What people seem to care about the most these days is saving money on electricity. You can save a huge amount on electricity by running the pump for far less time, and circulation will still be just fine with only 4 to 8 hours of pump run time (assuming a residential pool).

Also, many pools will not get skimmed effectively at the lowest possible speed. Skimmers need a certain minimum flow rate to skim effectively. Especially with the trend towards having more skimmers these days the lowest possible speed often won't be sufficient to clear surface debris, though this will vary from pool to pool.

Finally, "lowest possible speed" isn't always such a great idea. Most of the variable speed pumps currently available are less energy efficient at their lowest possible speed, hitting optimal energy efficiency at speeds just a bit higher than that.
 
Re: Hayward Tri-Star Variable Speed

JasonLion said:
In a technical sense, you are probably right. But it hardly matters. Far less circulation is perfectly fine in nearly all cases. There are a number of criteria to balance out. Circulation is just one issue among many, and not usually one of the more important ones.

What people seem to care about the most these days is saving money on electricity. You can save a huge amount on electricity by running the pump for far less time, and circulation will still be just fine with only 4 to 8 hours of pump run time (assuming a residential pool).

Also, many pools will not get skimmed effectively at the lowest possible speed. Skimmers need a certain minimum flow rate to skim effectively. Especially with the trend towards having more skimmers these days the lowest possible speed often won't be sufficient to clear surface debris, though this will vary from pool to pool.

Finally, "lowest possible speed" isn't always such a great idea. Most of the variable speed pumps currently available are less energy efficient at their lowest possible speed, hitting optimal energy efficiency at speeds just a bit higher than that.
Click to expand...

Hi Everyone, first and foremost is getting familiar with the Pump Affinity law.

Affinity Law (remember 3450 rpms at high speed)
• At ½ Speed (1725 rpms)
• Approximately ½ the flow
• ¼ the Head in feet (slower moving water creates lower TDH)
• 1/8the Electrical Consumption (approximately)

The key is everytime you cut the speed in half the energy used is reduced drastically. Here was a case study


WE HAVE A 23,000 GAL POOL (2”)
We determine that at 80% the VS Pump is pumping the same amount of water at the old Single Speed pump

At 80% 56gpm X 60min X 8hrs (26,880gals) 1013 watts an hour X 8 hrs = 8104 watts 8.1 KW
At 40%28gpm X 60min X 16hrs (26,880gals) 161 watts an hour x 16 hrs = 2576 watts or 2.6KW
At 30%22gpm X 60min X 22 hrs (29,040 gals) 86 watts an hour X 22 hrs = 1892 watts or 1.9 KW
At 25%18gpm X 60min X 24 hrs (25,920gals) 60 watts an hour X 24 hrs = 1400 watts or 1.4 KW

There are other variables to determining the lowest possible speed for a specific pool. I always like to say a pool is like a fingerprint, everyone is different.

1. Making sure the pool filter fills completely with water so the filter is able to do it's job.
2. Optimum skimming is obtained around 30-50gpm. Water tension is lost over 50gpm with most skimmers
3. Making sure all the equipment that is speed dependent is met (salt system, heater is pool is heater all the time, etc)

This is a great discussion and look forward to more comments. By the way, I am located in California where the electrical rates are high.

John the Hayward tech.
 
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Re: Hayward Tri-Star Variable Speed

You are preaching to the choir. Most of the regulars here on the forum are fairly well versed in the theory of pumps (see hydraulics 101 sticky in my sig) and especially the affinity laws. Being an Electrical Engineer myself, I understand the theory quite well.

However, affinity laws apply only to pumps and not motors or even VFDs so the electrical power draw does not change by a factor of 1/8th, it is the power delivered to the water (i.e. hydraulic power) that changes by about 1/8th. There is a relationship between hydraulic HP and electrical HP (wire to water) but for every pump with a motor, it is not 1:1 because both the motor and drive lose efficiency as RPM drops.

But I think you missed the point of our comments. The comments were not about the power savings of a VS, that is well known here. The comments were specifically about run time. The study I quoted showed that there was no significant improvement in water quality after about 2 hours of run time and the old requirement of a turnover per day is not necessary. So if there is no improvement in water quality after a few hours of run time, why are you recommending 23 hrs to your clients? This is a waste of energy no matter what the speed of the pump. Again, many people on this forum have found that short run times are just as effective as long even with a VS pump at low speeds.
 
Re: Hayward Tri-Star Variable Speed

mas985 said:
You are preaching to the choir. Most of the regulars here on the forum are fairly well versed in the theory of pumps (see hydraulics 101 sticky in my sig) and especially the affinity laws. Being an Electrical Engineer myself, I understand the theory quite well.

However, affinity laws apply only to pumps and not motors or even VFDs so the electrical power draw does not change by a factor of 1/8th, it is the power delivered to the water (i.e. hydraulic power) that changes by about 1/8th. There is a relationship between hydraulic HP and electrical HP (wire to water) but for every pump with a motor, it is not 1:1 because both the motor and drive lose efficiency as RPM drops.

But I think you missed the point of our comments. The comments were not about the power savings of a VS, that is well known here. The comments were specifically about run time. The study I quoted showed that there was no significant improvement in water quality after about 2 hours of run time and the old requirement of a turnover per day is not necessary. So if there is no improvement in water quality after a few hours of run time, why are you recommending 23 hrs to your clients? This is a waste of energy no matter what the speed of the pump. Again, many people on this forum have found that short run times are just as effective as long even with a VS pump at low speeds.
Click to expand...

I don't disagree as long as you are ok with throwing out turning all the water over in one day. If two hours keeps the pool clean I'm in, I just don't see that happening over a season. For water quality the APSP is still looking for the daily turnover.
 
Hello mas985; I can tell you that i am running at my clients pools only one and others two hours of circulation but that is because their waters are well balanced and sanitized, If you keep tour pH and chlorine on the range specialty on this cold weather you can get away with your goal, at the end of the day what people needs is save in water, chemicals, service, time and ELECTRICITY.


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That's good to hear and I agree that well balanced water is necessary but that is necessary for all pools and I also don't think it is a good idea to compensate for poor water quality with run time although I know some people will try to do that. We often hear about people running their pumps 24/7 to prevent algae but that is the wrong way to prevent algae. Proper FC levels for a given CYA level is the only way to prevent algae. However, if the extra run time is to keep debris out of the pool, then that is justified.

Technically, the only reasons to run a pump are to:

1) Chlorinate the pool - Manually dosed pool require little run time, SWGs may need more run time.

2) Circulate water (study says only 2 hours per day are required)

3) Remove debris - This is mostly aesthetics and depends on the pool owners tolerance for debris.

Since 1 & 2 can be done in less then 2 hours, IMHO the only reason to run a pump longer than 2 hours, is to remove debris or for SWGs. Right now, I get a ton of leaves in the pool so I will sometimes increase the run time to get the leaves out of the pool but in most cases, I just let the leaves build up and then use a leaf rake to get them out.
 
Two seasons ago we had a bad storm in the summer and lost power for 3 days. I lent the genny to a friend who at the time needed it more than I did. All I did with the pool was keep the FC in range and brushed it twice a day along with the kids swimming and moving water around. The pool had debris on the floor but was algae free. No pump or filtration for three days. ?
 

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That it is a great example, and should be proof that it possible to properly maintain a pool with very little run time or even no run time. Like your situation, there are plenty of other examples on the forum where they have been forced to maintain a pool without running a pump for several days and have been successful. Although not desirable, I think it may be possible to do that indefinitely.
 
I've had to do without pump or filter for several days as well. I did exactly what pwrstrk did and my water was crystal clear the whole time.

I would add to your list though:

4) Heating the pool - Running the pump is necessary to use the heater

I am running my pump 24/7 right now because I'm on a mission to achieve 85 degree water by tomorrow. :) It's 76 right now and climbing!
 
I neglected to post this in November, but we have the Hayward TriStar VS pump, I believe it's 1.85 hp. Based on actual KW from 15 minute intervals on a smart meter, here's the results:

100% output, 1.59 KW, 3450 RPM, 0% KW reduction
90% output, 1.17 KW, 3100 RPM, 26% KW reduction
80% output, .83 KW, 2750 RPM, 48% KW reduction
70% output, .58 KW, 2425 RPM, 74% KW reduction
60% output - never chose this one
50% output - .24 KW, 1725 RPM, 85% KW reduction
40% output - .14 KW, 1375 RPM, 91% KW reduction

So, as far as energy goes, you can run this pump 1 hour on full speed or 6.6 hours on 40% output with the same energy results. Your water movement does not follow suit but you can estimate run time and savings if you know the volume of water movement I suppose. Working for an electric utility, I am very pleased with the energy results.
 
In this old post I calculated the amount of energy for different speed settings but with varying times to get the same number of turnovers. So you can see that even increasing the time at lower speeds to get the same turnover of water is still significantly less expensive. Note also that at least with the Pentair IntelliFlo VF at that time, there wasn't any savings below around 26 GPM in my pool. At some point one runs into the fixed energy lost through electronics, resistance, and other factors not related to pump speed.

Now just because one can run the pump for a longer time at lower speed and save money doesn't mean that one needs to run the pump that long. One usually does not need to run for one turnover of the water. Running for some short times spaced out over the day (and even night) would work well for circulation so that water does not become stagnant for too long. That helps keep the chlorine distributed and preventing algae and pathogen growth. For skimming action, one may need to run the pump at a higher speed for a short time perhaps once per day. Finally, the number of turnovers needed is mostly a function of the amount of debris and bather waste getting into the water since the purpose of turnovers is primarily for filtration.

In practice in pools with solar pool water heating systems one may need to run longer at higher speed to get sufficient heating. For my pool, that's the main determinant of overall energy cost for the pump. The 48 GPM with the solar on is 1500 Watts while the 26 GPM with the solar off is only 275 Watts.
 
I just completed an OCLT for the first time :D and I am now moving on to running my pool normally.

In researching the proper run time of my pumps I came across this thread and had a few questions:

My 23000 gallon with pool with 2 skimmers sees a lot of sun all day (hardly any shade at all = about 12 hours of full sun on a daily basis). For the pool, I have the Pentair Variable FLOW pump paired with the Pentair Quad DE 100 filter. I would like to run it at the most efficient GPM (to save on my electric bill) while maintaining clean and balanced water per the TFP recommended levels. For the water feature (3 scuppers that are impossible to brush due to tight space and right angles), I have the Pentair WhisperFLO 1 HP pump. I believe algae was harboring inside the scuppers which, until I finally discovered it, was causing me quite a bit of frustration.

QUESTIONS: (assuming proper chemistry is maintained)

1. POOL PUMP What speed in GPM would you suggest (available range is 15 - 130 GPM)?

2. POOL PUMP What would be the minimum run time on a daily basis?

3. SCUPPERS PUMP Should I have to run it a lot (15+ hours a day) to keep the water moving through the scuppers? Will running it longer helper hold algae at bay?

Any suggestions?

Thank you!
 
1. Whatever works. This is no single answer to this questions. If you rely on skimmers to remove surface debris (e.g. don't use a pool cover), then look at the skimmer weir at different flow rates. The water should travel over the top of the weir. Otherwise it won't skim very well.

2. Technically, there really is no minimum other than what it takes to add and circulate your chlorine. It looks like you have a tab feeder? Are you relying on that for chlorination?

3. I would think that if you don't run the scuppers they would dry out and algae would not grow. Or does water stay in them? If so, only a few minutes a day should be necessary to replace the water with chlorinated water.

Also, what is your CYA level?
 
I've been using the Rainbow chlorinated but am transitioning to TFP method (bleach). It's hard to switch because the pucks are less expensive long term and are much more convenient. But I love the feeling of the simplicity of TFP method, it's just the constant monitoring.


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