Flow rates for heat pump chilling?

[akenis]

HP/Chiller has been sitting in my yard for over a month. Lota of work in extreme heat to replumb everything. Should have done it when it was cooler outside!

Anyway chillin now. 96 ... Hot tub like.

So HP flow rates are 30-70 gpm. Optimal 45. What does optimal mean?

What flow will cool the quickest? Does slower flow keep water in chiller longer? Or does faster flow take in more chillin?

Stuck with 1.5 " pipe, so 38 gpm is kind of max for pump efficiency, but I can run pump much faster. For now I don't care about pump efficiency, just want fastest cooling.

 

[ajw22]

I would run the HP with 45-50 GPM.

More flow will not give faster chillin or heating.

 

[akenis]

I would run the HP with 45-50 GPM.

More flow will not give faster chillin or heating.

What about 40 gpm. Would it chill slower?

 

[ajw22]

What about 40 gpm. Would it chill slower?

I doubt it.

Give it a test and see if you see a difference.

 

[akenis]

What about 40 gpm. Would it chill slower?

I talked to a Gulfstream engineer yesterday. Bottom line, he said he did all the tests with 56 gpm. He said I should run 50-55. He also said I was wrong and wasting money trying to chill during the day when it's 92 deg in FL.

What I was doing:
In the morning water temp was around 85. I thought it would hold until around 11. So I set pump to start at 11 am and pump 45 gpm. Keep that up until 5 pm thinking pool would not heat up much between then and sunset. Engineer was right. Heat pump ran the whole time. 87 deg by the time the cool cycle started at 11 am. Up to 89 deg by the end of the day. This is worse case scenario. 92 deg, no rain and no clouds. Coil temp was a degree or 2 below ambient. Not much of a chance for heat exchange.

Now:
HP more efficient at lower ambient and large difference between ambient and pool water. So start with 83 deg water and just let it bake all day. Maybe 88 by end of the day? Ambient temps don't really dip until about 2 am, to 82. And stays 82 until sunrise. So now running HP for 4 hours starting at 2 am when temp is low. More opportunity for heat exchange between 88 deg water and maybe 80 deg coil?

thanks for any advise.