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Old 10-26-2014, 02:18 PM   #1
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Pool Pump$$$

Noticed that NWBound had replaced an Arizona pool pump recently, so thought I would tap the resident wisdom. We have an unheated, chlorine sanitized, 14x21' inground gunnite pool. Has a sidewall suction port for the pool cleaning dohickey that wanders over the pool bottom. I figure about 9000 gallons. It currently has a Pentair pump with a 1 HP motor. Whisperflo. HAH! I replaced the impeller and bushings last year, which stopped the leaking and screeching, but it still seems unreasonably loud, and louder than when first fixed.

Local SoCal utility will contribute $200 toward certain multi-speed pumps when they have the money. I am very attracted by the idea of a pump that is quiet and uses less electricity. Some pumps claim to start slow and then use only the juice necessary to move the appropriate amount of water. When I read about them it mentioned that they only move 1/2 the volume, but for twice the time, which makes me think I'm not getting it, as that sounds like the same amount of work, and thus energy consumed.

This was suggested by a pool supply place:
Pentair WFDS-4 WhisperFlo Full Rated Dual Speed Energy Efficient 1HP Pool Pump, 230V
It doesn't qualify for an energy saving rebate.

This one does qualify for rebate:
Pentair 011018 IntelliFlo 3HP Variable Speed Ultra Energy-Efficient Pool Pump, 230V

I'm all a dither - as a non-swimming non-engineer short-time pool owner I know there is plenty I don't know. I do know the pool pump uses plenty of juice year round - we burn about 540KW/month when not here, at about $0.13/KW. My guess is the pump is responsible for ~$45-50/month. The pool stays operational year-round, and the utility company is talking a 8.4% increase.
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Old 10-26-2014, 03:46 PM   #2
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Yes, that's the crucial point: How does one save electricity with these new-fangled pumps? What I found out for myself is the following.

I also have a pool vac, the suction thinggy that crawls around the bottom of the pool, and makes the whole set up self-cleaning and low-maintenance (Hah!). In order for the pool vac to work, there has to be a certain minimal water flow through it to spin the internal rotor that animates its moving parts, like crawlers, feet, whatever have you depending on the brand and design.

So, the pump must be of a certain size to move that water. But I usually do not need that pool vac to operate longer than 1 or 2 hours each day. A longer run time is not necessary and will wear it out sooner. The "sucker" (it does suck up debris) is expensive for a plastic thinggy, and I want it to last. Yet, you want to move enough water through the pump/filter to have clear water.

Enters the fancy pump. Being electronically controlled, it has variable speed to allow me to set a high speed for the pool vac for only 1 hour each day, followed by 5 hours of low speed.

How does the above save electricity? Same as with a car, driving 2x the speed costs you a lot more gas to go the same distance. My beefy new pump has a top speed of 3200 rpm, but I set the high speed to a mere 2500 rpm, and its flow already surpasses my old mechanical 1-HP pump. For the low speed, I set it to 1500 rpm.

It displays the wattage that it uses. It's 800W for the high speed, and 210W for the low, a ratio of almost 4x for a speed ratio of 1.7X. The power penalty for speed is a lot higher with a viscous liquid, compared to air. I was shocked.

PS. By the way, these electronics pumps are very quiet. They have permanent magnets for the rotor, and share the same design idea as those inside electric vehicles. They are very powerful for the size and weight. And the ability to vary the speed allows you to set the optimal flow for your particular pool, filter, piping length, etc...
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Old 10-26-2014, 04:04 PM   #3
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Not an engineer, but an airplane pilot, and I think the fluid dynamics are similar with air and water. Air friction on an airplane follows the inverse square law, so going twice as fast takes four times the energy. That's why they spend so much time/money on smoothing the skin on an airplane, fairings, and such.

A real engineer will be along eventually and perhaps Nords or Gumby, both ex-submarine drivers, will drop in. I'd think those guys would be up to speed on water fluid dynamics.
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Old 10-26-2014, 04:10 PM   #4
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Ah, my memory is really fading, and no longer "superior" as I often claim (but it is still a lot better than that of people my age, I strongly believe).

And I remember now that when you get to turbulent flow, something measured with what's called "Reynolds number", things go down hill faster than the square of speed.
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Old 10-26-2014, 05:48 PM   #5
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One of the best pool investments I ever made was to go with a TigerShark which cleans independently of the pool pump and really does a great job. I have lots of trees so the pump based Barracuda/Navigator always had trouble. Put a timer on the pool pump so as to only run it on off-peak hours.
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Old 10-26-2014, 05:49 PM   #6
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I have an 18x36 inground salt water pool. Pump went out after 8 years (pretty good longevity). I run it almost year round. Polaris pump still operating fine. I found out about an electrical supply place that sells remanned pumps for a fraction of cost. I installed it removing 4 bolts, taking apart several pieces and replacing 2 seals that came w/ pump. Total cost $155 installed. The pool company usually charges $80/hr. and double cost of parts. You can watch YouTube videos showing you how.
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Old 10-27-2014, 12:10 PM   #7
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I went out to the backyard this morning. The new pool pump was not running. Uh Oh!

Walked up to the pump. The clear filter cover showed air. Flipped up the pump control panel cover. It said "Error. Self-priming failed". Relief!

Went to look at the skimmer basket. Yes, the thing was plugged up. High vacuum caused by the pump self-priming suction drew in air through the relief valve. The pump sensed that, so shut down.

These pumps all have a self-priming mode, where they initially run at a high speed (also programmable) for a few minutes, then settle down to the eventual operating speed. This new pump I have apparently can sense the load torque indirectly via power requirement, and shuts itself down as necessary to keep from running dry and ruining the seal.

My earlier smart pump that failed did not have some of the features this new one has, which is a Hayward EcoStar. I hope this new one will last. Or fails within the warranty period.

PS. It also has a built-in temperature sensor, and runs as necessary to circulate the water to prevent freezing damage. Not really necessary where I live though.
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Old 10-27-2014, 12:59 PM   #8
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A friend had a series of issues with her in-ground pool. Was permanently solved with a dump truck full of sand.
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Old 10-27-2014, 01:18 PM   #9
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It would take more than one load to fill in my 25000-gal diving pool. And as it means taking out my wife's beloved fruit trees, it's a non-starter.
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Old 10-27-2014, 05:13 PM   #10
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Originally Posted by NW-Bound View Post
It would take more than one load to fill in my 25000-gal diving pool. And as it means taking out my wife's beloved fruit trees, it's a non-starter.
OK, back to the pump repairs.
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Old 10-27-2014, 05:24 PM   #11
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Pump repairs, I have done for the last 25+ years.

Expensive pump replacement for one that last only 18 months, that brings out the animal in you.
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Old 11-02-2014, 12:02 AM   #12
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Quote:
Originally Posted by calmloki View Post
Local SoCal utility will contribute $200 toward certain multi-speed pumps when they have the money. I am very attracted by the idea of a pump that is quiet and uses less electricity. Some pumps claim to start slow and then use only the juice necessary to move the appropriate amount of water. When I read about them it mentioned that they only move 1/2 the volume, but for twice the time, which makes me think I'm not getting it, as that sounds like the same amount of work, and thus energy consumed.

I'm all a dither - as a non-swimming non-engineer short-time pool owner I know there is plenty I don't know. I do know the pool pump uses plenty of juice year round - we burn about 540KW/month when not here, at about $0.13/KW. My guess is the pump is responsible for ~$45-50/month. The pool stays operational year-round, and the utility company is talking a 8.4% increase.
Quote:
Originally Posted by Walt34 View Post
Not an engineer, but an airplane pilot, and I think the fluid dynamics are similar with air and water. Air friction on an airplane follows the inverse square law, so going twice as fast takes four times the energy. That's why they spend so much time/money on smoothing the skin on an airplane, fairings, and such.

A real engineer will be along eventually and perhaps Nords or Gumby, both ex-submarine drivers, will drop in. I'd think those guys would be up to speed on water fluid dynamics.
Pump hydrodynamics really suck, so to speak. Naval Reactors designed an entire reactor plant around natural circulation (the OHIO class submarine S8G reactor plant) because of the pump power, design, & maintenance issues.

I'll spare you the math, but it's a square law for pressure and a cube law for power. If you want to double the flow rate then you're going to use eight times the power. This is why boats (and airplanes) have a cruising speed and a max speed, and why they base their fuel-efficient operations on a much slower speed than they're capable of reaching.

This is a big deal in nuclear reactors, even when you have lots of power. My first submarine's venerable old 1960s S3G reactor plant (now used for training at the Navy's Nuclear Power School) would operate up to 50% reactor power when its coolant pumps were in slow speed. At that setting, the pumps used about one percentage point of the 50% power that the reactor was putting out.

If you wanted to go to 100% reactor power then you had to run the pumps in fast speed. (Woo-hoo!) When you did that, you really only had about 90% of that power going to the main engines (and the screw) because the steam-driven turbine generators would suck up nearly 10% of that 100% output just to make the electricity to run the pumps at fast speed. It used up so much reactor fuel, and reactor refueling overhauls got so expensive, that Naval Reactors actually monitored how often you ran your coolant pumps in fast speed and yelled at you if you did it too much.

The OHIO submarines are a nuclear-engineering marvel because they can run around with the coolant pumps shut off and the reactor operating just on natural circulation (hot water rises, cold water sinks)-- yet the boat still achieves an eminently respectable speed. (For a boomer, anyway.) The coolant pumps are usually not running so they're not making flow noise (or mechanical noise) and they're not putting 60 Hz tonals out into the ocean. (Yes, submarines can effectively hear electricity in the water.) Those boats are so quiet that they sound like rainstorms to a sonar operator, and at a distance the boats can actually be quieter than the ambient ocean noise. You look for the really quiet spots in the ocean (or the noisy rain squalls) and you follow them around until they drop a wrench in the bilge. Literally.

So, yeah-- you want a slow, quiet pump in your pool that runs twice as long instead of twice as fast. Ideally you'd have a pump that would run 24/7 at a very slow speed. Even more ideally you'd have one powered by solar panels so that it only runs when the sun is shining!
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Old 02-03-2015, 03:27 PM   #13
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What'd you know, my new and 2nd fancy pool pump failed after only 3 months!

When I saw a diagnostic failure message on the pump display, something about the PFC circuit failure (Power Factor Correction), there was nothing left for me to do but to call the pool store for warranty service. Good thing that I paid extra to buy locally and to have it installed, because calling the manufacturer for warranty would be a hassle. The local store also extended the warranty to 3 years, compared to the 1-year manufacturer warranty.

They sent out a service man the next day, and he swapped out the electronic module. He said it will get sent back to the factory, and I guess they would repair something this expensive.

By the way, I save on electricity with this pump by programming it to run at a high speed for only 1 hour to operate the pool vac, followed by 2 hours at a lower speed for filtration. At 3,000 rpm, the pump drew 1488 Watts as shown on its display. At 1,500 rpm, it was only 229 Watts. That's a factor of 6.5X power for a 2X factor of speed.

PS. Here's some more data.

1000 rpm - 98 Watts
1500 rpm - 229 Watts
2000 rpm - 485 Watts
2500 rpm - 900 Watts
3000 rpm - 1488 Watts

Between 1500 rpm and 3000 rpm, if we assume that the flow doubles so that the same volume of water can be moved in 1/2 the time with the higher speed, then 1 hour of the high speed run will burn 1.488 KWh, while 2 hours of the low speed run will take only 0.46 KWh or 1/3 the energy.
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Old 02-03-2015, 03:45 PM   #14
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I'm on my third 2hp pump motor in about 14 years of owning my pool. It runs about 10 hours per day and my Polaris pool vacuum runs off of this pump as well. I've done both pump motor replacements myself. Not too difficult if you first watch a YouTube video showing you everything you need to know. Changing them out isn't a lot of fun, but I'm not unhappy with the life that I've gotten out of my motors.


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Old 02-03-2015, 03:51 PM   #15
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My earlier non-electronic pump lasted 20 years, but required a motor change which I did myself. I have also replaced the shaft seal myself a couple of times.

The new-fangled electronic pump runs much quieter, and saves on electricity. But having two failed quite early means the payout remains iffy.
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Old 02-03-2015, 04:45 PM   #16
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Quote:
Originally Posted by calmloki View Post
... It currently has a Pentair pump with a 1 HP motor. Whisperflo. HAH! I replaced the impeller and bushings last year, which stopped the leaking and screeching, but it still seems unreasonably loud, and louder than when first fixed.

...I am very attracted by the idea of a pump that is quiet and uses less electricity. Some pumps claim to start slow and then use only the juice necessary to move the appropriate amount of water. When I read about them it mentioned that they only move 1/2 the volume, but for twice the time, which makes me think I'm not getting it, as that sounds like the same amount of work, and thus energy consumed... I do know the pool pump uses plenty of juice year round - we burn about 540KW/month when not here, at about $0.13/KW. My guess is the pump is responsible for ~$45-50/month. The pool stays operational year-round, and the utility company is talking a 8.4% increase.
I hope the data I provided above answered your question about energy savings and quietness with the new pump. I used to set my old pump for 6 hours each day, but found out that a daily run of 3 hours (2 hours at low speed too) is sufficient with the new pump to keep the 25000-gal pool clean. Not only that the new pump takes less power, I suspect that I had to run the old pump for a longer time due to its impeller getting so worn out and becoming inefficient.

Yes, I have swapped out the motor and repaired the shaft seal a few times, but in hindsight I was wasting money on the old and worn-out impeller and its housing. Erosion of the impeller and the housing increases the clearance between the two, and that reduces the flow. It was still running when I replaced it, but the flow was down to a trickle! And the noise was awful.

But if you get a new electronically controlled pump, pay for extended warranty if you can get it. These darn things have more "stuff" to fail.


Quote:
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... I'll spare you the math, but it's a square law for pressure and a cube law for power. If you want to double the flow rate then you're going to use eight times the power...
Well, basically drag force increases as the square of speed, and power being force times speed, that makes power goes as the cube of speed. In the case of my pool pump, it is less than 8X the power for 2X the speed. However, as it is not a positive-displacement pump, I suspect that the flow volume is not doubled for a speed doubling. I won't bother to measure the flow, however.
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Old 03-06-2015, 12:31 PM   #17
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An update on the pool pump electric usage.

I always believe that the variable-speed pump saves me money, based on its power consumption vs. that of the old pump. But I just now pull up records to have a more solid answer.

In the 12 months after the pump installation, I used 3,100 kWh less than the prior 12 months. In dollar amounts, it resulted in a savings of $263/yr. I have demand rate, so always run the pump during off-peak periods. The savings will be more if you have a flat rate. And in my case, I also had a 5% rate increase between the 2 years. If the rate stayed the same, my bill would have been close to $400/yr lower.
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Old 03-06-2015, 01:24 PM   #18
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I hope you get use out of your pool, we stopped using ours, so I was glad remove it and no longer have the expense and work of maintaining it.
It was above ground, so easy to remove.
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