Want to Save Energy

[acroy]

I'd like to save some $$ on Energy running the pool pumps. Can you experts review my pool and equipment and give me feedback.

Pool:
33,000gal in-ground gunite, Salt system.
Built 1986, re-plastered 2007
Everything is in beautiful shape – previous owners meticulously maintained it

Chemistry:
About 3,000ppm salt
50ppm borates per the Borate guide
pH maintained about 7.7
Alkalinity around 90
CYA around 70ppm
Cl around 2ppm. The water has stayed clear and beautiful thus far but temp is only about 72f.

Equipment:
Main pump: 1.5hp AG Smith Centurion
Secondary pump: 1hp Emerson (pulls from output of main pump & feeds salt cell)
Salt cell: Clearwater LM2-24
Filter: Sta-Rite System 3 DE, 53sq feet

Pumps ran 2hrs/day winter (under 70f), 4hrs/day 70f+ so far. So far so good.

Energy:
I’d love to save some $$ by going to hi-efficiency motors and/or installing a VFD to slow the pumps, and run longer. I can get an industrial vfd through work for around $200. However, if I do that, the suction-side vacuum will not work.

Also the Guide for salt-water pools say to run the pump for 8hrs+, which sounds very spendy.

What's some good options to save money on power? Can the salt cell operate OK at reduced flow?

Feedback? ideas? Thanks!

[mas985]

Putting a VFD on a conventional pump will likely reduce the life of the motor The pump motor needs to be designed for a VFD and most residential pool pumps are not.

A new variable speed pump is always an option such as the Intelliflo but is expensive. Also, a two speed pump will give you most of the benefit of a variable speed at a much lower cost but then you only have two speeds to work with. You can run it on high for the vacuum and on low for other times.

Other options include replacing the just the motor with a two speed and/or the impeller. Although a smaller impeller will also reduce the flow rate of the pump and may impact the cleaner.

If budget is not a consideration, I would go with a variable speed pump. It will give you the most flexibility and performance. Otherwise, a two speed is not a bad option.

[Davegvg]

I have a Jandy Epump, and find I can get my suction side cleaner to work just fine using about 300-350 watts of power. I think you are better of buying a new variable speed pump designed to cool at the lower speeds that uses the rare earth (permanent) magnets delivering about 30% more efficiency overal.

The chlorinator stays happy down to about 200 watts then begins display low flow fault warnings.

This nets out to about a half HP of power, and I use a dragonfly skimmer when not using a bottom cleaner and run at the same power setting.


Dave

[acroy]

Thanks for the feedback!

I'll start running the numbers and see what makes sense. I played with the system a bunch yesterday, it works just fine with only the 1.5hp main pump running and the 1hp pump off.

If I can get away with a single 1.5 or 2hp 2-spd, it may be the best option. Looks like they're not too spendy to install. I suspect the additional 1hp pump was slapped on with the salt system a few years ago and is not necessary. It runs in series with the main pump, after the de filter. I see little difference in pressure @ the de tank with it off or on, about 2psi.

As far as a vfd on a normal motor: as far as I'm aware, usually the only issue is overheating @ very low speed due to reduced air circulation. Rule of thumb in the industry I work in is 30% or better, no issues.

[acroy]

ps - my goal is to save $$ - any investment needs to have a 18-24month ROI or better!

[mas985]

As far as a vfd on a normal motor: as far as I'm aware, usually the only issue is overheating @ very low speed due to reduced air circulation. Rule of thumb in the industry I work in is 30% or better, no issues.

VFD rated motor, "inverter duty", will usually have better insulation and better bearings. The PCM waveform causes additional currents in rotor which can discharge across the bearnings and shorten the life of the bearings. In addition, the insulation ratings need to be higher than a standard motor to account for the voltage transients. Some articles discussing some of the issues:

http://motors.automationdirect.com/Info ... mpare.html
http://www.ien.com/article/preventing-vfdac-drive/7666
http://www.est-aegis.com/TechPaper.pdf
http://www.pdhengineer.com/courses/e/E-1007.pdf

I know of one VFD manufacture that was targeting residential pools pumps and had to stop selling them because there were too many failures. Now they sell them only for a select few pumps that are VFD rated. You could just try the VFD and see what happens. Worst case is that you will need to replace the motor at which point you can substitute an inverter rated motor.

[acroy]

INteresting - Thanks