Vs pump and pool heater

[smooth2222]

Example, vs running at half speed vs full speed going thru a pool gas heater.

How much efficiency do you lose thru the pool heater at half pump speed vs full speed?

Curious question.

I know running at full speed would be more efficient at heating the pool.


Another question,

When heating the pool, how much efficiancy do you gain by setting pool filter at recirculate vs running thru filter. I have a sand filter.

 

[needsajet]

I'm sure someone with more experience will come along, but in the meantime you heater should have specifications for minimum and maximum flow, which need to be respected. Usually longest life for the heater will be in the lower end of the specified flow range, but more heat will be transferred at the higher end of the flow range, as you mention.

At optimum flow, the heater is perhaps losing 15 or 20% of the energy input. Any reduction of energy transferred to the water will make this worse. For example, if you run the heater longer by running at low flow, you'll lose the savings in electricity by pumping at a lower speed.

The filter is usually the greatest source of head loss in the system, so if you don't need the filtering and you do need heating, recirculate could be used to achieve the flow you need. I'd be worried about forgetting to set it back to filter, but that's just a practical thing. Switching from filter to recirculate in my systems yield a flow increase of 40% on low speed and 50% on high speed.

As far as quantifying efficiency loss, it's fair to say that your questions are very complex. There are people here who could handle it, but a great deal of detail would be needed, if they were willing.