Sizing of a Wood fired pool or Wood fired hot tub heater

To size your heater you will need to know the approx volume of water in your pool or hot tub. Then use the chart to determine approx heat up times by the BTU output of each heater. Remember the output ratings are MAX BTU and will vary depending on type of wood and flame level.

Heating Rate* of Various Size Wood Heaters

Water Volume

Water Mass

Temperature Rise °F/hour  

 US Gal  lbs  Small (35MBH) Medium (55 MBH)   Large 105 (MBH)
 100  833  42.0    
 200
200 1666 21.0
 1666  21.0    
 300  2499  14.0  22.0  
 400  3332  10.5  16.5  
 500  4165  8.4  13.2  
 600  4998  7.0  11.0  21.0
 700  5831  6.0  9.4  18.0
 800  6664    8.3  15.8
 900  7497    7.3  14.0
 1000  8330    6.6  12.6

 2000

 16660

   

 6.3

 3000  24990      4.2
 5000  41650      2.5
 10000  83300      1.3
     *Excludes heat loss of tub/pool   
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