Best pump speed when heating?

[michaelr0]

We recently had some kids over and needed to get our pool heated from the upper 65 to 85F. What is the best pump speed for the pool to heat up the fastest? I have a Pentair 300k BUT heater and a Penair Superflo VST. I have the pump set at night to run slowly at 1400. The heater ran all night, however, the next morning the pool was only at 72. It occurred to me that the pump speed was too slow to circulate the water efficiently. I increased the speed but between life and a wife meddling with the settings as well, I can't say for sure, if it went any faster.

Any feedback/advice is much appreciated.

 

[JamesW]

You want 30 to 40 gpm.

 

[Randrx2]

The short answer is: no, increasing the flow rate does not heat up the pool faster.

The heat transfer is effected by the difference in temperature of the 2 systems (heater and water). Your heater is rated at 300k BTU per hour. That means you will only get that amount of heating.

If you increase the speed of the pump, the water temp as it leaves the heater will go down some, however, a greater volume of water will be heated. As you slow down the pump, the water temp as it leaves the heater will go up, however, a lesser volume of water will be heated.

You are still transferring the same amount of heat into the water.

The heater will have a recommended flow rate. Set your pump for that flow. Ideally you want the pump to run at the best speed for effective skimming and filtering. If that speed falls within the heater suggested flow, use that speed.

 

[michaelr0]

Thank you! That makes perfect sense. I am slapping my forehead for not thinking of that myself. The Pentair manual states the heater needs min 30 gpm and max 120 gpm. As you said it will not matter much and key is effective circulation and skimming.