Pump Speed While Heating

[cnr1089]

First season with a pool (well, it finished at the VERY end of last season, we didn't have time to use the heater other then to make sure it works).

I have both a Propane heater and a heat pump. It has been pretty cold around here, but it will be 70 at least 3 days this week (and the kids are off from school), so we are itching to use the pool. Right now the water fluctuates between 47 and 55 degrees (night to day).

Anyways, time to try out our heater and make the pool usable this week (need to cut our solar core to fit our pool, hope to do that tomorrow when things dry out).

I have a mutli-speed pump. Is the heater as efficient when the pump is running low speed? I would figure since the water flows through the heater slower, then it would have more time to heat up and it would not make things less efficient.

What is the thought? Especially since we will probably be running the heater (propane for now) for about 24 hours in a row to get the pool up to swimmable temperatures.

 

[JasonLion]

With a 400k BTU heater you need a fairly good flow rate to keep the heater working well, probably 40 GPM or more. I'm not sure if your pump moves that much water on low speed or not. It would depend on many details of your plumbing.

 

[mas985]

I have a mutli-speed pump. Is the heater as efficient when the pump is running low speed? I would figure since the water flows through the heater slower, then it would have more time to heat up and it would not make things less efficient.

Heat loss is dependent on the temperature differences so the hotter the water, the faster the heat will be lost so lower flow rates result in poorer efficiency. Not much different than a solar heater. Plus, the hotter water is in the pipes longer at lower flow rates so more time to lose head so again, the efficiency will drop some.