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heating a pool with wood boiler

Gary_15 Member Posts: 22
I did this for a customer a couple years ago. They have an Aquatherm outdoor wood boiler that we had tied into their home oil-fired boiler. We added a stainless steel heat exchanger and ran a circulator pump just for the pool heat loop. The manufacturer suggested a flow switch in the pool pump loop to detect circulation and an aquastat to read the pool water being circulated through the line. This way the circ pump will not run if the water is up to temp or if the pool pump is not running. It has worked well for a couple seasons now. I was surprised at how quickly you could feel the warmer water flowing from the pool jets. Works great if you keep a wood fire going all season to heat the pool. They did keep it running anyway because the wood fire heats their domestic water.


  • Paul Bunnell
    Paul Bunnell Member Posts: 1
    heating a pool with wood boiler

    Hi! I am in my second year in the heating trade after switching over from carpentry. So I have a lot to learn. My problem is to find the best way to hook up a used Van Wert wood/oil boiler to heat my 21,000 gallon pool. Since I plan to use wood as the heat which does not come on and off like oil. I am wondering if others in the trade would offer some constructive advice. Respectfully
    submitted Paul
  • Mike Thomas_2
    Mike Thomas_2 Member Posts: 109
    150,000 btu

    If you really want to heat it, you will need at least 150,000 btu. No contact with iron components, so probably a heat exchanger.
  • hot_rod
    hot_rod Member Posts: 22,147
    return temperature protection

    would by one concern. The boiler will want to see at least a 140 return temperature to avoid sweating (condensing) I'd probably go with an injection mix into a stainless steel pool heat exchanger like the Triangle tube brand.

    Pool heaters usually get sized by the surface area not the gallon capacity, not the gallon capacity.

    If you "google" pool heaters you will find the formulas to calculate pool heaters based on the temperature rise you wish to see. Pool covers make a bit of difference also, as the large loss is across the surface.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ALH_4
    ALH_4 Member Posts: 1,790
    Pool heating

    I'm not sure this is the best application of a wood boiler. The pool temperature could fluctuate quite a bit depending on when and how hot the pool was heated. You have a relatively narrow band of comfortable temperature in a swimming pool. If you want to keep the pool between 76°F and 82°F, you have approximately 8 hours between firings of the pool at design heat load (I am assuming the design heat load with an outdoor pool in a northern climate).

    It seems like heating a pool with a wood boiler, you would want to size for a relatively quick heat-up rate so the owners dont have to start firing up the wood boiler the day before they want to swim.

    I like the idea of solar collectors with a backup heater better than the wood boiler, depending on the insolation in your area. The wood may be free, but I have a feeling it will be a pain to run, and will lessen the owner's satisfaction with the pool.
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