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Proper heater size is based on the time required to heat pool or spa to the desired temperature.
- If water is heated for each intended use and rapid heating is desired, a larger unit is required.
- If water is gradually heated to the desired temperature and then maintained at that temperature, a smaller heater may be acceptable.
First determine desired temperature rise per hour using the chart below:
Temperature rise per hour formula:
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_____
desired water temperature (�F) |
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minus |
_____
average air temperature (�F) |
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equals |
_____
required temperature rise (�F) |
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divided |
_____
required hours to heat to desired water temp. |
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equals |
_____
required temperature rise per hour (�F) |
Gas Pool Heater sizes are determined by their BTU* output. Use the chart below to determine BTU required to raise the water temperature depending on the pool size.
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POOL SIZE - SQUARE FEET |
| sq. ft. >> |
300 |
400 |
500 |
600 |
700 |
800 |
1000 |
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BTUs |
Desired Temperature Rise in �F per hour |
| 200,000 |
1-1/2� |
1-1/4� |
1� |
1� |
3/4� |
- |
- |
| 250,000 |
2� |
1-3/4� |
1-1/2� |
1-1/2� |
1� |
3/4� |
- |
| 300,000 |
3� |
2� |
2� |
1-3/4� |
1-1/4� |
1� |
3/4� |
| 400,000 |
3-1/2� |
2-3/4� |
2-1/2� |
2� |
1-1/2� |
1-1/4� |
1� |
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SPA/TUB SIZE - GALLONS |
| gallons >> |
300 |
400 |
500 |
600 |
500 |
800 |
1000 |
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BTUs |
Desired Temperature Rise in �F per hour |
| 200,000 |
59 |
45 |
36 |
30 |
25 |
22 |
18 |
| 250,000 |
84 |
63 |
51 |
42 |
36 |
32 |
25 |
| 300,000 |
104 |
78 |
63 |
52 |
45 |
40 |
32 |
| 400,000 |
128 |
96 |
77 |
64 |
55 |
48 |
38 |
* BTU stands for British Thermal Unit. A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
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Gas Heaters for
Inground Pools |
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| Gas Heaters for AboveGrnd Pools |
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