To VS or not to VS...

[NLITP]

I may be in need of a new pool pump soon, as my current one is very old. To summarize, I've calculated it costs $255.09 / year to operate my current, single-speed 2HP pump. A service guy recommended a Pentair Intelliflo iF2 Variable Speed pump (model 011009 - 2HP Max). After a rebate from my electric company and a rebate from Pentair, the total comes to $1,024 installed. At this rate, it would take roughly 4 years to break even on the cost of installing the variable speed pump IF MY SAVINGS PER YEAR IS 100%!!! Pentair and Hayward savings calculators typically use higher energy costs and running the pump for 8 hours a day as defaults, which inflates their estimated savings.


Furthermore, the running schedules for a 2HP pump vs a VS pump doesn't seem to equate to any real savings (though I don’t have any real numbers to prove it). For example,


2 HP motor: 4 hours (minimum 3 for vacuum to clean the pool and an additional hour for the water to turn over once)
VS motor: 3 hours @ higher RPM (for pool vacuum) + ??? hours to finish turning the pool water over once)


Can anyone tell me what I’m missing or where I’ve messed up the numbers? I like the idea of a more efficient, quieter pool pump to save energy (and money) and like the idea of the pump running longer for circulation, but it doesn’t seem like a “home run” to go with the variable speed pump given the above. Any advice is appreciated.




———————
The Numbers
———————
Pool Size (in gallons): 18,000
Pump HP: 2


Feet of Head: 60-70 ft.
Pump Flow rate @ 60ft of head: 103 GPM
Pump Flow rate @ 70ft of head: 86 GPM
Time it takes to turn over 18,000 gallons 1 time: 3 - 3.5 hours, so conservatively, 4 hours


Pump's observed energy usage: 2.08 kW
Energy usage for 1 day (2.08 kW x 4 hrs): 8.32 kWh
Energy usage per month (8.32 kWh x 30): 249.6 kWh
Energy usage per year (8.32 kWh x 365): 3036.8 kWh


Current energy rate: 8.40 cents/kWh
Daily Energy Cost: 8.32 kWh x 8.40 cents = $0.70
Monthly Energy Cost: 249.6 kWh x 8.40 cents = $20.97
Yearly Energy Cost: 3036.8 kWh x 8.40 cents = $255.09

 

[pabeader]

Pool turn over is something we rarely consider here. You run at high for the vacuum and run at a lower speed for skimming. Your pool gets plenty turned over during vacuuming.

 

[ping]

Read this article, Determining Pump Run Time.

With VS pumps it is ideal to run the majority of the time on low speed, around 1000 RPMs, and only run at high speed when needed for those features such as the vacuum.

 

[mas985]

If you are only interested in economics, they really don't make much sense for a VS at that energy costs. Also, if you compare the lifetime cost to a two speed, you will find that the two speed will be much lower.

You can run the two speed on low speed for the same 4 hours and use about 1/4th energy or about $64/yr. Plus, if you just replace the motor, you save the hassle of re-plumbing the pump.

 

[NLITP]

Thanks for the responses. So, for the sake of the conversation, lets assume the 4 hours I currently use to run my 2HP pool pump is sufficient.

So, same question... would it pay off to go with a variable speed pump? Running my 2HP pump for 4 hrs a day vs. running a variable speed pump for 12(?) hours a day. Keep in mind I'd still have to run the variable speed pump for a minimum of 3 hours at a higher RPM for the vacuum to do it's job. So, in this specific example, I would be saving the cost difference of running the 2HP motor for 1 hour vs. the cost of running the VS pump for 9 hours (since 3 hrs at a higher horse power is required no matter which pump).

- - - Updated - - -

With a 2-speed, I'm guessing I'd need to run at the higher speed for 3 hours (for vacuuming) and then a few additional hours on low speed to equate to 4 hours of my 2HP pump(?). But, I like the idea of being able to just replace the motor. I've become more handy of late, so maybe I could do it myself.

 

[NLITP]

@mas985 - Yes, but I think I'd have to run the VS Pump for 3 hours at a higher RPM for the vacuum and then the equivalent of 1 hour of my 2HP pump. If low speed is 1/2 hp, maybe that would be 4 hours @ low speed + 3 hours @ high speed. I do like the idea of just replacing the motor... maybe I could do it myself.

 

[mas985]

3 hours for vacuuming? I run mine 1 hour per day.

Depending on the vacuum and the valve setup, it may be possible to vacuum on low speed as well.

Low speed is half the flow rate of full speed but that does not mean you need to run twice as long. Again, run time should not be dependent on turnover. Turnover, simply doesn't matter. What matters is that you have enough time for chlorine circulation (1-2 hours max) and enough time for the cleaner to remove debris (depends on the environment and your own tolerance to debris).

So, same question... would it pay off to go with a variable speed pump?

Compared to what? Your existing pump, yes, eventually it would pay off. However, compared to a two speed, the extra cost of the VS over the two speed may not be made up for over the life of the pump at those energy rates.

 

[chiefwej]

I replaced an old single speed pump with the Pentair VS 011018, which is a 3 hp pump. I picked that model for its flexibility. With its onboard timer control and ability to be controlled externally it suits my needs perfectly. Even if there were no savings in energy, I would have still spent the extra money on this pump, for its quite operation and flexibility.

I have an in floor cleaning system, a solar heating system, and a salt water chlorine generator. The old pump drew 2,800 watts and ran about 8 hrs per day. It also did a lousy job of keeping the pool clean. My system is pretty simple, no automation, just an old Intermatic pump timer and a SolarTouch controller. The new pump cost $850 less $150 rebate (which covered installation). It was hooked up to the hot side of the Intermatic timer, leaving the SWG on the switched side. My new pump runs a total of 18 hours a day, cleans the pool and filters much better, while using much less electricity and being mostly silent.

0500-0800 Cleaning. 2,800 rpm 1300 watts
0800-1600 Chlorinating 1,200 rpm 138 watts
1600-2300 Extra Filtration 1,000 rpm 100 watts

My solar controller is connected to the pump and when heat is called for, and is available, it opens the valve and ramps the pump up to 2,500 rpm (900 watts) to heat the pool.

I could cut my run time way down but that 7 hours a day of extra filtration makes the water just sparkle, and it's only equal to a single 100 watt bulb, and I like the idea of the SWG being on during the height of the day.

 

[NLITP]

@chiefwej - Did you:

a) buy the pump online for $850 and then pay someone $150 to install it?
b) buy the pump from a service (who also installed it) for $1000?
c) other?

I'm up in Phoenix and haven't found it at that price point through any local vendors.

 

[chiefwej]

I bought the pump online for $850. At the time there was a $150 rebate available from Pentair if the pump was "professionally installed". Pentair didn't have a list of authorized installers so any electrician, plumber or pool service that can give a receipt for professionally installing the pump qualified for the rebate and a three year warranty (vs the DIY 90 day warranty). BTW: I added the Pentair couplings/unions to my order. Very worthwhile.

 

[swimcmp]

One thing to think about I started using Intelliflos 9 years ago when they first hit the market. I have two that are all original never had anything other than a sshaft seal put in them. No drives no motors so if a replacement motor is 250-300 and you replace those every three years or so you have an additional saving there. I have four pools that are Paramount systems with Intelliflos that run enough flow to keep the floor system operating at recommended flow rate, running 24 hrs a day and the owners love them.

 

[mas985]

No drives no motors so if a replacement motor is 250-300 and you replace those every three years or so you have an additional saving there.

I am not sure I understand this comment. A standard pump motor should last well over 10 years if maintained properly. If it isn't then something else is wrong. One of the most common failures of a pump motor is that the seal failed first and water got on the bearings rusting them. But that can happen to any pump VS or not.


However, replacing a VS drive, costs nearly as much as a new pump. Several on this forum have reported failed drives that fell way short of a 10 year expected life span. So I don't think they any more reliable than a standard motor.

 

[yangcha1]

I bought the pump from Amazon for about$850, too. It is a great pump, very quiet and efficient. I missed the rebate. But anyway I installed it myself.
Amazon.com : Pentair 011018 IntelliFlo Variable Speed High Performance Pool Pump, 3 Horsepower, 230 Volt, 1 Phase - Energy Star Certified : Swimming Pool Water Pumps : Patio, Lawn Garden

I bought the pump online for $850. At the time there was a $150 rebate available from Pentair if the pump was "professionally installed". Pentair didn't have a list of authorized installers so any electrician, plumber or pool service that can give a receipt for professionally installing the pump qualified for the rebate and a three year warranty (vs the DIY 90 day warranty). BTW: I added the Pentair couplings/unions to my order. Very worthwhile.

 

[chiefwej]

Usually a failure in a VS pump is caused by lightning or other power surges. After all it is basically a computer running a big motor. To avoid problems I adde a whole house surge protector. $110 and it help protect all my home electronics.

 

[rdshackleford]

I take it a step further and put a surge capacitor and lightning arrestor on my panels, in addition to the whole house surge protector. They run about $30-$40 each.

Usually a failure in a VS pump is caused by lightning or other power surges. After all it is basically a computer running a big motor. To avoid problems I adde a whole house surge protector. $110 and it help protect all my home electronics.

 

[mas985]

Just make sure you get a decent surge protector. They are not all the same. Also, location can be important too.

5 Things to Know About Whole House Surge Protection - Page 5 of 5 - TecHome Builder

The Myth of Whole-House Surge Protection - Article from CE Pro