Advisability of retrofitting to a two speed pump

[Sentient]

We have a two year old in ground gunnite pool with a Sta-Rite MPRA6F-148L 1.5HP single speed pump. Our electric company is offering a $250 rebate for pool owners who retrofit to a two speed pump and promise to run it during the night or morning hours only. This sounds like it might be a good deal, but I am unaware of the ramifications of such a change. The pump feeds a Sta-Rite System 3 Modular media filter, Sta-Rite SR Heater, and Goldline Controls Aqua Rite Chlorine generator. The whole setup is controlled by an Aqualink RS 8 controller.

Will going to two speeds actually save electricity, and if so, can anyone point me to information on how I should go about estimating the savings?

Will the SWG work on the low speed setting?

The pool currently uses a Poolshark Vacuum that is manually set to work with the current pump, how do I make it work with the two speed? Do I add a valve controller and program it to use it exclusively on low speed, or the other way around? Perhaps it should be off on low speed and used only on high speed.

I expect I should be able to sell the old pump on Ebay to recoup some of the cost of upgrading, does that seem viable to the old pros out there on this site?

Thanks in advance for any thoughts or suggestions on the subject.

Sentient

[mshumack]

i have 2HP 2-spd pump on a 20,000 gal IG pool. I can offer these observations:
Pool cleaner will not work on Low speed (I have a suction side cleaner, StaRite Great White).
The SWG will work fine on Low speed.
The water movement on Low speed is amost undetectable on the surface (so skimmer is not very effective on Low). I have to put my hand in front of return fitting to tell if water is moving.
There is not enough flow (accroding to panel light) to run Heat pump when pump is on Low.

I have an Automated Controler (IntelliTouch) that lets me program when the pump goes to high speed - such as when the cleaner is On or if Heater is On. I believe you mentioned that you have automed control as well so you should be fine in this respect.
Good Luck

[MarkC]

I also have a 2 speed pump (2.5 hp) that runs on low for 95% of the time. My pool sweep has a booster pump and this works fine on low. The heat pump usually does not have a problem on low speed but when the pump basket is getting filled with dog hair it sometimes won't start. The flow through my system on low is noticeable and the skimmers work fine.
For the person who has problems with the heat pump not running on low you can sometimes adjust the pressure switch in the heat pump or downsize the return eyeball size just a bit in one eyeball to create a little more back pressure.

[Sentient]

Thank you both for your observations. I am still hoping to hear from folks offerring pointers on how to estimate electricity savings, if any. It sounds like the pump is run on low for long periods of time, so I am not sure that actual power use is lower. I want to make sure I will be able to see a difference in my electric bill before proceeding.

My cleaner operates on the suction side, so it sounds like it won't run on low, which is fine, I can put in a valve controller and turn it off completely on low so all return is via skimmer and drains, and set it to optimum flow on high. The controller will just have to have a stop set in the optimum flow place. I hope they are available that way. It loooks like a little experimentation may be needed.

Our electricity is mostly natural gas based, so the prices are just getting higher and higher with no end in sight.

[mas985]

Sentient,

A two speed pump will nearly always save you money assuming you run the pump on low speed most of the time. If you go with the same HP pump but in two speeds, the lower speed will have about half the flow as high speed so the turnover is twice as long. This means you will have to run it twice as long on low speed than high speed for the same filtration. The power usage at low speed for some pumps is about 30% of high speed (60% reduction). But since your running the pump twice as long, you will save close to 30% of the power than high speed.

Even without the rebate, the savings would pay for the pump in about a year.

[Sentient]

Sentient,

A two speed pump will nearly always save you money assuming you run the pump on low speed most of the time. If you go with the same HP pump but in two speeds, the lower speed will have about half the flow as high speed so the turnover is twice as long. This means you will have to run it twice as long on low speed than high speed for the same filtration. The power usage at low speed for some pumps is about 30% of high speed (60% reduction). But since your running the pump twice as long, you will save close to 30% of the power than high speed.

Thank you, that helps a bunch. So now I just need to pick a pump. There is a two speed version of the pump I have now, so I presume plumbing it in should be relatively straightforward, the dimensions should be identical. I think I will go ahead and do it.

I thank you all for the quick feedback and great information.

Sentient

[cgc2]

How many gallons is your pool ?
A two speed pump will save you money. I have a 30k gallon in ground pool, running a Autopilot SWG (cell upsized for 60k gallon pool), and a Automatic Pool Cleaner (Dolphin).
I run a 1hp Pentair Whisperflow @ 4hrs high, 5 hrs low, and it keeps my water sparkling clean and with a Clorine level of 2.5-3.0 ppm.

BTW....I live on the other side of the Grapevine and work for the utility co. offering you that rebate.