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Variable Speed Pump Question

Posted by trainthewoods (My Page) on
Tue, May 24, 11 at 9:30

We signed on a new pool build last week & I've been pretty happy with everything I've seen/heard about the company we're using.

One thing that takes me for a loop is, I asked the PB multiple times about using the Jandy epump & he has told me that it won't work properly with a saltwater pool. I've spoken with a few people that disagree with him. It seems crazy to me to not use an energy efficient product, when it's available.

I'd like to force the issue, can someone explain to me the process to run a variable speed with saltwater? Thanks in advance!


Follow-Up Postings:

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RE: Variable Speed Pump Question

trainthewoods,
Variable speed pumps work on the same principle. You have a selection of speeds that you can set. Salt based chlorine generators require a minimum flow rate to function. I am not aware that Jandy has any problems doing this. Minimum flow rates required by most generators is around 15 to 20 gpm's.
Perhaps your PB is just not familiar with the operation/function/installation of variable speed pumps. Ask him if he has installed any? Some PB's still have not installed any because they are more expensive, may require a separate controller, or are afraid of the technology.


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RE: Variable Speed Pump Question

i just went through the bid process and imo you are dealing with a pb who is not familiar with variable speed pumps and he just makes up any excuse why he doesn't want to install one. i had nearly the same situation with one of our bids. we did not use this pb.

pool builders need to realize that future owners are more knowledgeable than they might think and they better get on the variable speed bandwagon or risk losing many bids.


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RE: Variable Speed Pump Question

Yeah, that's kind of the idea I get too.

I sent an email this morning & was told it would work, but he didn't think it was necessary.

Realistically, how much energy should it save each month? It's a $950 upgrade over the 2.5hp Stealth (which he said is what they generally use).

I'm going to go for it, but I'd like to be able to quantify it to him...and my wife.


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RE: Variable Speed Pump Question

from my research it can realistically save you 50% on your electric bill.....about $40 per month instead of $80 to power your pump.

it should also only be about $400-$500 to upgrade pumps:
http://www.inyopools.com/pumps_jandy.aspx


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RE: Variable Speed Pump Question

A VS is certainly better than a single speed pump but so is a two speed pump. A two speed pump can capture most of the savings of a VS pump and in a lot of cases, the two speed can actually have a lower lifetime cost than a VS pump.

For example, with a 15k pool, 1 turn per day and $0.25/kwh, it can take a VS 120 months of operation to save more money than a two speed pump. Basically to make up the %500 cost differential. On the lower speeds, the VS may use 100 watts less power but that requires 20,000 hours of opeartion to make up the cost difference.

Don't get a VS for JUST the cost savings. If you need the flexibility of a VS, it is a great solution but it isn't always the most cost effective solution.


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RE: Variable Speed Pump Question

Good point mas985.
Quote - "For example, with a 15k pool, 1 turn per day and $0.25/kwh, it can take a VS 120 months of operation to save more money than a two speed pump. Basically to make up the %500 cost differential. On the lower speeds, the VS may use 100 watts less power but that requires 20,000 hours of opeartion to make up the cost difference."

I have been crunching the numbers myself to see if there would be any benefits from us going from a single speed to a two speed or variable. Our electricity runs about $0.11/kwh, and we have no spa included in our pool. We have a Polaris 280 with a booster, and a waterfall with its own pump. As best I can tell, it would take us about 4-5 years just to recoup the cost difference from a two speed, and about 13 years to recoup the cost of a variable speed. Unless my math is wrong, it just doesn't seem worth it to me, based on our setup. Our pump is the Hayward Tristar, 1hp, and our pool will be ~14K gal. If you guys see some error in my calcs, please let me know.


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RE: Variable Speed Pump Question

trainthewoods...I'm a big fan of 2 speeds also for the reasons mas985 mentions. We have two 2 speed pumps that do much of the work for our pool and the energy used at low speed is about the same as energy used with a VS at lower speed. Our pumps are Jandy 2 speeds and have been in operation for 5 years now...no problems...just mentioned this since your PB is offering Jandy products and this may be an option you can ask about.

wahama...no errors in your calculations...it will certainly take longer to recover the added initial cost of VS technology. Any payback period longer than 10 years is risky in my opinion due to average life cycles of pool pumps. Also, a drive failure alone on a VS pump will cost as much to replace as a brand new 2 speed pump.

Hope this helps.


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RE: Variable Speed Pump Question

Awesome! Thanks for all the insight!

I'm not sure whether I need the flexibility or not. I'll have a Polaris 280, 3 bubblers & a spill over from the hot tub into the pool. Also, a dedicated booster for the water features.

Also, I don't understand how it could take up to 10 years to recoup costs. If the VS saves me $40/month & the upgrade is $750, I calculate a little over a year & a half to break even. What am I missing or not taking into consideration?

Thanks again everyone!


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RE: Variable Speed Pump Question

In all honesty, unless you are paying $0.50 kwh, I can't see that you would save $40/month. Electric rates and usage have just about everything to do with payback. From what I have read, anything under $0.20 kwh, you are looking in the 7-10 year payback cycle for a VS, since they are about 3x the cost. Not as bad if you goto 2 speed. There is a great worksheet on TFP that you can enter your own data and pump options as well as your kwh cost, and it will estimate your monthly cost for the main pump. This is where I figured out my "stuff."

VS may work great for Cali, but its tough for me to justify here in the Houston area.

I'm no pump expert, but I play one on the internet :)


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RE: Variable Speed Pump Question

trainthewoods....the $40 monthly savings that brg88tx mentions is comparing a VS to a 1 speed.

The monthly savings is more like $3-5 per month when compared to a 2 speed. This range will vary depending on energy rates and daily pump run times and speeds.

There's not much difference in energy consumption between a 2 speed at low speed and a VS at low speed. This is why the payoff periods are longer for a VS when compared to a 2 speed that is priced significantly lower than the VS.

Hope this helps.


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RE: Variable Speed Pump Question

Here are a couple of links that I used to figure out my data:

Hayward energy calculator -
http://www.haywardnet.com/inground/products/energysolutions/calculator.cfm

I would assume that Jandy and the others have something similiar, but our PB uses Hayward, so that is the one that I looked at. Based on my kwh cost and run time for 1 turn per day, this calculator shows that I would save $16.22/month for a VS over a single, and $8.59/month for a 2 speed over a single.

Using the worksheet at TFP, it shows me the following:
Using a 2speed over a 1speed would save me $4.36/month. Using a VS over a 1speed would save me $9.21/month. This is "assuming" I entered my stuff right, which I think I did. The worksheet can be accessed here:
http://www.troublefreepool.com/pool-pump-energy-cost-comparison-t18378.html

My assumption is my true savings would fall somewhere in between the two.

A 2speed is the most viable option for me, but in all honesty, based on our personal situation, I don't know if we'll still be here in 5 years, so I'm keeping the cash, and buying some palm trees :)


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RE: Variable Speed Pump Question

Boy, I think anyone who does not use a variable speed pump is ignoring the advantages of new technology and energy savings. I believe all the major manufacturers of equipment have a calculator on their web site that lets you calculate your personal savings based on what you pay for electricity, how big your pool is, how long your pump will run per day. The savings is phenomenal. Payback for my customers is typically within 12-18 months. If you are being charged a higher amount for the pump, then it could take longer for payback. Don't ignore this new energy savings tool!


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RE: Variable Speed Pump Question

wamaha...good links to the calculators and your results sound about right...our electricity rate is $.07/KWH and the savings of a VS over a 2 speed was about $2.50 per month...not a big deal so we went with the 2 speed pumps and saved lots of money on initial costs and system complexity...no regrets.

womanowned...this so-called new energy savings tool has been around for over 30 years in other industries (adding VFD's to motors). When it comes to pumps, either air moving or fluid moving, the laws of physics are at play. Pump affinity laws (google it) are what causes the dramatic decrease in energy with reduced speeds...not the motor technology itself.

VS technology adds a drive to the motor design which adds complexity to the pump design. VS designs also have more parts to fail down the road and when they fail, they are expensive....example a capacitor failure on a 2 speed pump will cost about $20 to replace while a capacitor failure on a VS drive will cost over $650 to replace.

Why burden the homeowner with added initial costs and replacement expense when a 2 speed can deliver almost the same efficiency with a simple design that is easy and inexpensive to maintain.

My 2 cents.


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RE: Variable Speed Pump Question

vs pump = permanent magnet motor
single and 2 speed pump = induction motor

permanent magnet motors are far more efficient.


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RE: Variable Speed Pump Question

brg88tx...your statement is misleading..permanent magnet motors are only about 4-5% more efficient than today's high efficiency induction motors.

Here's the breakdown for 2 pole motors as we're discussing here:

1 phase Induction Motor 88-89% efficient
3 phase Induction Motor 90-91% efficient
Permanent Magnet Motor 92-93% efficient

The only difference between a permanent magnet motor and a 3 phase induction motor is the rotor itself, which has permanent magnets embedded in it instead of aluminum bars to induce the magnetic field.

The biggest contributor to pump efficiency are the laws of physics. Google pump affinity laws....pump power exponentially gets smaller as pump speed decreases...it has very little to do with motor efficiency.

This is why there is not much difference in energy efficiency between a 2 speed at low speed and a VS at lower speed. This is also why the online energy calculators will not show much difference between the two technologies when calculating monthly energy bills.


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RE: Variable Speed Pump Question

Personally, I would not trust any tool from a manufacture that is trying to sell you a pump. That is why I developed my own spreadsheet using the data published by the California Energy Commission. The manufacture tools generally use gross approximations and tend to use unrealistic scenarios plus they don't show you how the calculations are done.

You can download the CEC data yourself or you can download the spreadsheet below and do the analysis yourself. Unlike the manufactures web site tools, I built a completely transparent tool open for full review so I am not trying to hide anything from the user.

But it really only takes simple math to prove the case of a two speed pump in some situations. Assuming decent plumbing and using the CEC data from Curve-C, a Whisperflo WFDS-24 will produce about 42 GPM @ 380 watts while an Intelliflo will produce about 30 GPM @ 140 watts for a difference of 240 watts. This may seem like a big difference but the money saved is not all that great.

In a 15k pool and a turnover per day, the Whisperflo requires 357 minutes on low speed while the Inteliflo requires 500 minutes for the same turnover. So the Whisperflo uses 2.3 kwh/day and the Inteliflo uses 1.2 kwh/day or a difference of 1.1 kwh/day. Again, it sounds big until you apply the electrical rates. So if your electricity rate is $0.07/kwh to make up the $500 cost difference between the two pumps you would need about 6500 days (>200 months) of run time before the Intelliflo starts to be more cost effective than the Whisperflo.

However, you can make the case for the Intelliflo by changing some of the assumptions. For example, if the electrical rate is $0.30 like in CA and the user was running two turnovers per day, then the Intelliflo will become more cost effective than the Whisperflo after only 750 days (25 months) which makes the Intelliflo the better choice. However, some POs need to run their pumps at higher speeds for part of the day to run cleaners and/or solar so that can diminish some of the benefit.

Even though we have high electricity rates here in CA, I chose the two speed because much of time I run the pump at higher speeds for solar so the benefit of the VS was not as great for me. You can see my situation in Scenario 3 of the spreadsheet. I modified a 1 HP Northstar pump to create a 1/2 HP two speed pump but was able to do that for only $120 so it would be hard for any pump to beat that lifetime cost.

Anyway, you can run all of these different scenarios using the spreadsheet.

Here is a link that might be useful: Pump Cost Calculator


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RE: Variable Speed Pump Question

mas985's spreadsheet is awesome.

This is real world data for different pump technologies in application...I agree...this is better than the pump manufacturer's energy calculators and kudos to the California Engergy Commmission for the work they have done to generate this data.

Looking at the CEC data, there are some VS pumps that actually use more power than their 1 speed or 2 speed counterparts at higher speeds...this is due to wasted drive energy in the form of heat at the higher current levels.

If you own a VS pump, be aware that higher speed operation is costly. Try to minimize high speed operation whenever possible.

mas985 also brings up another good point...if you're contemplating a VS or 2 speed or 1 speed, keep in mind the application. If the pump will be used on higher speeds most of the time i.e.; cleaning, solar, running other water features, etc...the energy saved diminishes quickly.

Using his spreadsheet, one can make informed decisions.

Thanks mas985!


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