The link below is data from the California Energy Commission. They had many different pumps tested using exactly the same plumbing curves. Unfortunately, the curves used are for very poorly designed plumbing systems but at least it is a fair comparison between the pumps.

Also, you need to take into consideration as to what the RPM values is for each of the VS pumps since they are not consistently the same.

Here is a link that might be useful: Pool Pump Data

I forgot to add that Curve A is a bit more realistic than Curve B although both represent very high head loss plumbing systems.

Also, column M is the best metric to compare pumps because it represents gallons pumped per watt-hr of energy use.

MAS985

When I click on the link you posted all I get is a spreedsheet of pumps listed. Am I doing something wrong?

Thanks

Yes, the spreadsheet is what you should get. All the new VS pumps are listed plus a bunch of two speed pumps. Each pump has a set of measured data for both plumbing Curve A and Curve B. Curve A is more realistic of the two and can be expressed as:

Head (ft) = 0.0167 * GPM^2

This approximates a plumbing system of 1.5" pipe 220 ft of equivalent lenght. So it is quite pessimistic but it does allow you to compare pumps on the same plumbing.

The first row of the spreadsheet contains the information for each column which includes the pump model, HP, Service factor, motor efficiency plus it has the GPM and Watts used for each plumbing curve. Column M has the metric that I was talking about earlier which is the gallons pumped per Watt-hour of energy use. This tells you directly how efficient the pump will be relative to others.

Your plumbing is likely to be better than Curve A so both the GPM and Watts will increase a bit but the GPM should increase more than the Watts so your situation should be a bit more efficient.

So if I'm ready the spreadsheet right it confirms what's in Pentair's published curves which is that their pumps using ECM motors are very efficient at low flow rates. Some of this comes from lower friction in the pipes but the pump motor itself is playing a big part too.

BTW the Pentair trailer stopped at the local pool contractor a few months back with a test setup where I could vary flow and head while monitoring rpm and power consumption. I confirmed a couple of points on the published curves which was nice and then ran some more data points to fill in between what was on the chart. So if anyone is wondering if they can trust the power consumption numbers Pentair publishes I'm pretty confident the answer is yes.

BTW I'm planning on using the VF. The pools uses venturi skimmers which only take about 6-8 gpm each so the system only needs about 16 gpm to operate. I still get one turn a day and the power consumption is about the same as a couple of light bulbs.

With venturi skimmers that 6-8 gpm takes a little bit more energy than a standard pool return.

Pentair has always been conservative in their numbers.

That's a very good point. The venturi is going to raise the back pressure somewhat. It will be interesting to see how much (I'll post numbers). Still given my oversized pipes and filter and careful attention to valving plus the fact that the flow rate is so low to begin with I'm sure my overall system will still have substantially less back pressure than a typical setup running at 45 let alone 65 gpm.

What I'm getting at is that I see a lot of discussion about how to design a system for reduced energy consumption, much of which seems to me misguided. It a no brainer in my book to increase pipe diameter and pay close attention to all the other parts of a good design like sweeps in order to reduce friction losses. But if the system is set to run at high flow rates for a couple of hours a day instead of low flow rates 24/7 then that is like driving a car at 120 mph for 15 minutes and parking it for 45 rather than driving it continuously at 30 mph. You're going to use a lot more energy getting the same work done because resistance goes up nonlinearly.

Any system is going to operate much more efficiently at low flow rates. A well designed system with reduced friction will operate better than one that that is poorly designed and a system that uses an ECM motor in the pump will operate (particularly at low rpm) far better than other motors (assuming equal pump design).

Hi sb...good to see you back here talking system efficiency again. Looking forward to seeing how your system performs when completed. I like your use of venturi skimmers for efficient skimming action. I think you will find that the bottom of the pool will still need cleaning. Unless it's a small pool that can be cleaned manually with a net/brush, you will still need some high speed power to help with the cleaning chore. Unless, of course you implement a robotic cleaner.

Keep us posted on your results...if you can truly get away with ultra low speed operation at a few hundred watts, you may want to look at a small solar collector system which can supply the few hundred watts to the pump easily. There is a new HVAC heat pump on the market that has its own collector to power just the fan motor....just wanted to share that idea.

That would be the ultimate pool filtration system..free of monthly bills.

The solar collector could also be used for charging the robotic cleaner if so equipped.

Hope this helps!

I will have a robotic cleaner (see my other post asking for help in selecting one). The pool also has an automatic cover which must be closed at all times except when people are actually using the pool because it is our only safety system (no fence).

Solar PV is not a good investment, except for cases where there are rebates that make the system essentially free (which basically means someone else's electricity or taxes are going up to pay for your system). Besides pumping is only a tiny component of the energy consumption of a pool. Far larger is the cost of heating. I believe this is true even in warm climates but its certainly true here in Portland, OR even if you are only using the pool during the summer season.

To that end I've spend a significant amount of attention on this area. Rather than having a gas heater or dedicated heat pump I've gone with a tubular heat exchanger that heats the pool using the same residential heat pumps the house uses for heating and cooling. This not only avoids buying duplicate equipment, which saves significant capital expense, it permitted me to upsize the exchanger (at a modest cost) so that I can heat when pumping at only 16-20 gpm.

Although I've chosen to go with a VF pump for flexibility and ease of programming (plus the additional efficiency that an ECM pump affords, particularly at low speeds) the result is a system that can run at one very slow speed. This is extremely important because it means the techniques I've employed could be applied to the broader market where cost is important consideration by just swapping out the VF to a very low HP single speed pump or dual speed pump. The pumping cost would be significantly higher than using the VF but the overall system cost would not be that much different for most regions since heating cost swamps pumping cost. This would be a very good low cost solution, certainly far better than the way most systems are designed today (run at a high flow rate for a few hours a day).

Finally it provides and excellent solution to a problem of another poster...how to equip a pool that needs to run off grid. If power is scarce one simply cannot do much better than running an ECM motor equipped pump at very slow speed 24/7 and heating with solar. The capital cost is higher than other designs but when you don't have access to the grid that doesn't matter.