Help figuring out time and speed of variable pump for salt water pump and heat pump

[istreich]

We finished about 6 weeks ago a salt water pool 40 ft x 20 ft with approx. 28,000 gallons. The pool is protected by a Coverstar automatic pool cover whenever we don’t use it, including during the day

It is heated by an Aqua-cal Heatwave 166,000 btu heat pump

And we have a Pentair IntelliFlo variable speed pump. And we use a Pentair 520 cartridge filter.

The chlorine is generated by a Pentair IC40 unit. And all is controlled by a Pentair Intellitouch system with iPhone/Laptop. interface

I am trying to optimize the duration and speed of the variable speed pump. Right now, I have it running for 24/7 at 1800 RPM which (if my calculations are correct, based on tables I have found and using watts displayed by the mobile app) generates roughly 45 GPM.

I called AquaCal (heat pump) and they mentioned that the water pressure for their heat pumps should be between 30 and 70 GPM and their “sweetspot” is around 45 GPM. Obviously, to be the most energy efficient, you want to run this pump (if not 24 hours) when it is the warmest during the day (probably day time).

At the same time, I have to make sure I generate enough chlorine via the SWG (not an issue right now as my chlorine was through the roof at 60%-1800RPM 24/7).

I also need to make sure I run the pump long enough to “refresh” the water.

At the same time, I am trying to minimize any energy “waste” (and costs). I have talked to various folks and suggestions range from one hour at max power per day to 24/7 at no less than 1700rpm but also (probably more correct) less than 24 hours a day at a certain minimum with maybe one hour or “max rpm”…

I have to admit I am a little confused and trying to have a more “scientific” approach to the problem.

At 1800rpm 24/7, I probably need to reduce my SWG to 20% or less (especially with cover). If my math is correct, it looks like I refresh all my pool water in 10.5 hours which may be an overkill. But I am also trying to maximize use of heat pump while outdoor temp still allows it (Georgia).

Any suggestion on the “right” answer?

It looks like 12 hours a day at 1800 rpm during the day may be the best compromise. But I am concerned it may not be long enough for the heating to work…

Thanks a lot for your help figuring this out.

Note: We use a Polaris legend pool cleaner with a separate booster pump. Any suggestion on how long this should run, knowing that we have an automatic cover.

 

[chiefwej]

Your heat pump is the controlling factor. It requires a higher flow than the SWG and a longer run time. As far as filtration and "refreshing" your pool water, that is not an issue. The old concept of rate of turnover has been disproved. As long as the water looks good you are getting plenty of filtration. Even a couple hours a day should do that. So you want to run the pump at the lowest speed that works with the heat pump and the minimum time required to maintain your desired temp.

That said I do run my pump 17 hours a day, but the vast majority of that time is at 1,000 rpm (100 watts). I have my SWG on a separate timer so that it is only on 7 hrs per day.

Re pool cleaner, like filtration just looking at the pool should answer that. With a covered pool it shouldn't take much. Start with say 2 hrs and adjust it by 15 min each time until you find what works for you.

 

[JayG]

Funny, I've been wondering the same thing: how to work with run times and gpm with a heat pump to maximize efficiency/minimize energy use.

You might try playing with the Ray-Pak heat pump calculator:

http://roxwebdev01.pixelgate.net/gas_sizing/Pool_size_Raypak.php

It can give you an idea of how many hours you might need to run your heat pump to achieve your desired temp. You can input all your parameters and then keep reducing run time until the unit cannot maintain temp for the month you are in. That run time (or something a bit more to build in some leeway) would be where I would start (and program those times during the warmest time of day). The calculator is built around Ray-Pak pumps which don't correspond to your AquaCal exactly, but it will give you an idea. It seems with your cover and your SWG you have plenty of capacity to generate enough FC in a 6-12 hr pump run time (which might be all you need to run your heat pump through November and early Spring). Like Chief pointed out, how much or little you run your pump beyond your heater needs seems entirely dependent on your pool and preference for pool clarity.