Energy Efficient Pool Pump

[BStone]

My first post. We live in the southeastern US and put our pool in just under 2 years ago. I don't know very much about the ins/outs of the pool so please bear with me.

Our electric bill is averaged out so that we pay the same for 12 months and then it adjusts. We have seen great increases since adding the pool. My power company recently did a home audit to help us find ways to lower the bill. They found the pool pump using 1.5-1.6 KW per hour. I do have a timer. My pool is a 16X36 rectangular pool with a 8.5' deep end. So I assume it's around 26k gallons. I currently have a Pentair Easy Touch Control system with a one speed, one hp, Pentair Superflo pump. I'm trying to decide if a variable speed pump or 2 speed pump will help. My concerns are will operating on slower speed affect my salt water system? I have Pentair saltwater chlorine generator. Will it help lower costs? My pipes are 1.5" and I eve contacted Pentair. They said I need to determine TDH to determine correct pump. I haven't gotten good response or information from my pool company. I was thinking of a Pentair Superflo Variable Speed or perhaps an Ecopump. Just want to lower my monthly costs without sacrificing quality of the pool water.

Thanks for any help.

[mas985]

You don't need to calculate TDH to choose a pump. That's complete nonsense. In most cases, choosing a pump is not all that difficult. But it does depend on your unique situation.

But before deciding that you actually need a new pump, you may just need to change your run time. Most people don't realize that a typical pool may need only about 3-4 hours of run time per day. They simply have never tried it so they don't know. For those that have tried a drastic reduction in run time often find that the pool doesn't look any different or any dirtier. So I would try that first before deciding on a new pump.

The second step that leads to even more savings is swapping the pump motor with a two speed motor.The SuperFlo is a really good pump so swapping the motor would be a good option for you and should be a lot cheaper than going with a VS. What size (HP or model#) is your current pump? Would you feel comfortable doing the work yourself? There are a lot of videos on youtube on how to replace motors.

The third option is to go with a VS pump. However, I really only recommend that for areas with very high electrical costs (e.g. California, NE, Hawaii). Because of the cost difference between a VS (with surge protection) and a two speed can be close to $500, it takes a very long time to pay that off unless electrical rates are very high. Given your location, I think you would be better off with a two speed pump.

[PoolDoc]

Here's the SuperFlo brochure: http://www.pentairpool.com/pdfs/superfloDS.pdf

I checked prices on both a replacement 2-speed motor (~$300) and a complete new 1HP 2 speed pump (~$400). For that difference, I'd recommend replacing the pump, and saving the existing pump for spare parts. There is a new issue this season: Pentair has shortened the warranty on equipment sold directly to the user, so . . . install the pump IMMEDIATELY on receipt. Most likely, with a small pool like that, you can leave the pump on LO, except when you are backwashing the filter. Links below. The pump below is listed as having a switch on the motor case, so you may not need any wiring changes. But, I've also listed a DPDT switch of the type you'll need for external switching.

Pentair SF-N2-1A SuperFlo Energy Efficient Two Speed Inground Pump with Switch, 1 HP

Eaton 7810K1 Extra Heavy Duty Toggle Power Switch, AC/DC Rated, Screw Terminal, On-On Action, DPDT Contacts

[BStone]

The current pump is a 1.0 hp. Sorry for leaving off. Thank you both for the information.

[BStone]

Just a quick follow-up. Looks like this pump will help me with my energy bills. I can also experiment with the amount I run it. I guess that would generate less chlorine with a salt water system? Can you run salt water systems on 4 or so hours a day? Also, I read the technology of the vs pumps by itself makes them more energy efficient? True? Or is the savings only from running at slower speeds. Sounds like it still would not be worth the additional cost based on price difference between the 2 speed and vs. Sorry to ask so many questions, but just want to make sure I make the correct choice.

[PoolDoc]

The SWCG cell's output is not related to flow, unless the flow is so low that the salt level between the plates is depleted. But the IC-40 has a flow switch that will shut the unit down before that happens.

VS pumps are slightly more efficient than a properly selected (ie, small as will work properly) 2 speed pump -- but they are MUCH more expensive, complex and considerably less reliable in areas subject to voltage spikes (read: thunderstorms!).

Educated engineering decisions are *always* a trade-off -- there are no perfect choices, or perfect pools, much less perfect engineers.. My experience has mostly been with very large commercial pools, usually designed by a practicing engineer -- and there hasn't yet been a pool lacking a dozen 'designed-in' problems. Even the two pools I designed have some flaws!

Beating yourself up trying make that ideal choice won't help you enjoy the pool: whatever choice you make, I already know it won't be perfect! However, making a "good choice" is often a achievable goal.

[mas985]

Can you run salt water systems on 4 or so hours a day?

I can run mine on 4 hours per day at about 85% (2 hours in winter) so you might need a little more run time but it depends on your SWG output.

I read the technology of the vs pumps by itself makes them more energy efficient? True? Or is the savings only from running at slower speeds. Sounds like it still would not be worth the additional cost based on price difference between the 2 speed and vs.

Yes the VS is more efficient at all speeds but the savings may not be enough to pay for the extra cost of the pump during the life of the pump.

Here is an example of an economic study I did comparing various pumps with $0.10/kwh and 4 hour run time (1 hour high, 3 hours on low). It takes the Intelliflo over 130 months of operation before it becomes more cost effective than the two speed. The pump may not last that long given reported drive failures by other users and that fact that most pumps don't last that long. I didn't even include the surge protection for the Intelliflo which would make it much worse. The fact is that when energy costs are cheap, it takes a long time to pay for itself over a two speed. BTW, you won't see this type of analysis on Pentair's site because they want to get into the more expensive pump and so embellish the energy savings. Also, note the cost per month. If run properly, all the pumps are pretty cheap to operate. Yes the SuperFlo costs about twice as much to run but that is only $3.50 per month difference so it takes quite a while before that can add up.

[PoolDoc]

Very interesting, Mark. A couple of questions:

1. Why do you have the 2-speed pumps set to run for an hour on high, every day?

2. Why does do the two Whisperflo pumps have such different efficiency? (65% vs 51%)

3. What sort of motor does the Tristar have, to have such a good efficiency value? (I've heard some not good things about Tristars locally, in terms of reliability, though. Not sure how valid those reports are, but people seem to be having more problems that they would have with a SuperPump. But then the SuperPump may be the gold standard in terms of operational reliability.)

I didn't realize the motor efficiencies were that low, or that they varied so widely.

[mas985]

1) It is some arbitrary but most POs with two speeds find they need at least 1 hour per day at high speed for better skimming and a cleaner. Low speed usually doesn't work so well for both of those things including myself. I can't create a scenario that fits all pools so I make the workbook available for those who want to customize it: Pool SpreadSheets

2) Larger motor (>HP) generally have better efficiency only because they use larger wire to handle the current. Also, the motor type makes a difference. Anything with a run capacity such as a Permanent Split Capacitor (PSC) or a Capacity Start Capacitor Run (CSCR) motors are more efficient than the motors with just a start capacitor. But for the Whisperflo, the main difference is HP.

3) Depends on the TriStar. The standard two speed pumps have CSCR motors which have better efficiency. The TriStar VS is an ECM permanent magnet motor. BTW, what sort of problems are they having? I know Hayward has had some issues with bad seals over the years which a third party manufactures so unfortunately they get the bad rap for it.

[PoolDoc]

The TriStar VS is an ECM permanent magnet motor. BTW, what sort of problems are they having? I know Hayward has had some issues with bad seals over the years which a third party manufactures so unfortunately they get the bad rap for it.

I don't know. I got the reports second-hand from the assistant manager of the local wholesaler. Like I said, I don't know how indicative those reports are -- and in my experience, every pump comes off second-best compared to the SuperPump's reliability which has dominated this local market. But, I'll try to remember to ask him for details the next time I see him . . . when he has time to talk.