solar prefers SLOWER flow rate and electric heat pump requires FAST flow rate? How will this work?

AGP noob

Well-known member
Apr 8, 2021
60
dublin,ca
How do other people do this? I am reading pool solar (Fafco) prefers "slowish" flow rates for efficiency and electric heat pump require FAST flow rate? How will this work combined in the same water piping circuit? I would get a diverter so I can use either the heat pump or solar isolated but my questions below are is it possible to use them together...

If I were to run it like this
pump > filter > electric heat pump > solar panels on roof > pool

Will the flow rate required for the heat pump (ie. 1500 GPH or more) be too fast for the solar?
Will solar panels on the roof slow down the flow rate too much for a electric heat pump to work?
If I were to buy a two speed or variable speed pump will that be pointless because the electric heat pump will require the highest speed (for high flow rate) to run? Therefore just get a single speed?


Thank you!
 

kevinskii

Gold Supporter
Aug 6, 2019
171
Los Angeles, CA
Pool Size
1
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
We have an array of 9 Uma Sunstar panels. It's similar to what Fafco makes. Each 50 sq. ft panel requires 5-7gpm nominal flow rate, which is 45-63gpm total. A rough rule of thumb is to have your solar array the same size as your pool surface area.

However, I don't think there's a reason to run solar and the heat pump at the same time, and I'm not sure that a heat pump would be a good choice for San Ramon. You might be better off with solar and gas heat, or just solar. Heat pumps generally are better if you have prolonged cloudy weather, but they require a lot more energy than solar and heat much more slowly than either solar or gas.

Either way, you're looking at a decent investment. Adding on a variable speed pump would not cost that much extra and would be much more efficient while allowing you to tune the flow rate according to the equipment's needs. For example, I run 45gpm when the solar is on, 41gpm when using the gas heater, and 28gpm otherwise.
 

AGP noob

Well-known member
Apr 8, 2021
60
dublin,ca
got it thx
Yea i cant do gas. I was thinking solar and heat pump combo would be good during the shoulder months (april/may and oct). The lows are in the mid 40s so I'll have to see if solar can keep up w/ the heat losses (and yes I use solar cover).
Thats good to know about the 5-7gpm of each panel. If this is the ideal flow rate for solar then it seems like electric heat pumps and solar systems flow rates do not match well and should not be run together. (unless you have a ton of panels)
 
Last edited:

kevinskii

Gold Supporter
Aug 6, 2019
171
Los Angeles, CA
Pool Size
1
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The max flow rate depends on the manufacturer. I don't recall mine offhand but it's quite high, and it's specified as a burst pressure. My 3HP Intellifo VSF pump could not even reach the high end of nominal, let alone max.

For reference, I have pretty much perfect solar conditions (single story south facing roof near pool equipment, lots of sun), and I'm able to maintain temperatures around 82-84F using solar alone in the shoulder months starting around April and ending in November. I can keep my pool at around 85-88F from May through August at least. Your season might be a month or so shorter.
 
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