Smallest possible pump size inquiry

[LarryInSanDiego]

Hello folks. I figured this was probably the most applicable section of the forum to ask this. When I first planned my pool, I hired a well respected local pool forensics/inspector, Rick English. In our discussion about pumps, he stated that a very small pump running around the clock was better than a large one running for a few hours per day. His point was with a small pump, filtration and chlorination was constantly happening as opposed to water stagnating for long periods with the large pump. Obviously, a large pump would be needed for vacuuming and spa jets, so multiple pumps would be necessary. I don't recall the pool size he mentioned, but he said an engineer friend of his was getting excellent results running a 1/4 hp pump.

With my 32K gallon pool, that means I would need a little over 22 gpm flow. I've been considering a 1/15 hp Waterways pond pump 3410020-1E. It's rated at 40 gpm with no head but still flows at 22 as long as pressure doesn't exceed 6 psi at the filter - that's IF I'm interpreting the chart right. I plan to replace the cartridge filter with a 60 sf Pentair DE filter. With a smaller pump, I would expect lower back pressure at the filter due to lower flow, providing I keep the filter cleaned. I have a second DE filter and am considering using the lesser restricted DE filter for small pump use (I already figured out an automatic controller circuit for turning on the larger pump for the pool heater, but that's for another discussion).

Does anyone here run a <1 hp pump 24/7?

This looks like the right group of folks who would know. Thanks in advance.

 

[YippeeSkippy]

Hmmm....the lowest I've seen mentioned (that worked well) was 3/4 hp.

Yippee

 

[pooldv]

I have a 3hp Intelliflo variable speed pump. I often run it 24x7 at 1100 rpm for skimming, filtering and making chlorine with the SWG. We have lots of trees and need the skimming to keep debris in the skimmer baskets and off the pool floor. Our pump uses 150 watts at 1100 rpm. Our electricity cost 10.25c/kWh and it costs less than 12 bucks per month to run the pump. My filter pressure is 0 with my pump running 1100 rpm.

 

[Jimrahbe]

Larry,

Welcome to TFP.. A Great resource for all your pool questions, even if they are about incredibly small pumps... :super:

I have the same Intelliflo as pooldv, and run my pump 24/7 at 1,200 RPM. I do ramp it up a few times a day to increase the skimming action. Overall, it costs me less than $20 per month.

I like the idea that my SWCG produces a steady output of chlorine throughout the day and think it helps me maintain a more stable FC level.

My cartridge filter pressure at 1,200 RPM is only 2 or 3 psi... I also have two rent houses with the same set up, but with DE filters, they also have very low filter pressures.

Thanks for posting,

Jim R.

 

[JamesW]

Variable speed is the way to go. You might have rebates available. Maybe consider adding automation to control pump, solar, SWG etc.

EasyTouch with WhisperFlo might be a good choice for you. With variable speed, you don’t need multiple pumps, just adjust speed as needed. Automation can change speed for gas heating, solar etc.

Rebates Guide | San Diego Gas Electric

 

[Teald024]

I have a 3hp Intelliflo variable speed pump. ..... uses 150 watts at 1100 rpm.

That 150 watts is just a tick less than 1/4 hp. A pump motor will only consume the power needed to meet the requirements of the system.

Larry, if you actually measured the power consumption of your 1.5hp (rated) pump motor, you would likely find that it is not running anywhere near the rated power. If you wanted to "upgrade" your system, you would probably be better off buying a two speed or vs pool pump instead of a pond pump. For that Waterways pond pump 3410020-1E, you may want to check your numbers again. It looks like it is rated for 0.63A @230V which would be about 1/5hp (not 1/15hp). As you acknowledged, using that pond pump would still require a larger pump for cleaning, heating, etc. I

t seems like a less elegant solution to use that smaller pump. Just go with a single multispeed pump and use your controller to set the speeds as needed.

 

[needsajet]

I don't doubt that you could make your plan work, but a high efficiency two speed or VS pool pump is designed for exactly what you describe. The other wrinkle you may not have considered is skimming. Sometimes you want the pool skimmed quickly after winds or a storm or before a party, while agreeably most of the time long run times at low watts do just fine. Your mate the pool guy is right, and exactly what low speed on a pool pump is for.

 

[LarryInSanDiego]

Thank you everyone for your responses. This one perked my ears, especially since I could not find any info from Pentair about energy consumption at any specific combination of parameters:

I have a 3hp Intelliflo variable speed pump...uses 150 watts at 1100 rpm...

Given motor service factors all over the place, there is no such thing as a pump at peak efficiency at all speeds, and that Pentair's tech support told me that energy performance charts are for in-house use only (he would not release any info and hung up on me - telling perhaps???), Pentair's published performance charts are useless to me because amperage for any of the given curves is not one of the published parameters. I'm not sure just how much more efficient I can go with going with more than one pump, I'd just like to know that I made the best possible choice of pump(s). Btw, at the given data point above, would you happen to know the flow rate?

 

[JamesW]

The flow rate depends on the rpm and the head loss. The IntelliFlo has a published head curve that will show flow rate at rpm and head loss.

 

[pooldv]

I run the pump at 1950 rpm to run solar and it uses 550 watts. And I run it at 1500 for the heat pump and it uses, dang, I can't remember. Probably 250 or 300 watts.