Swimming Pool and Spa – Gas & Propane Heaters

Gas-fired pool heaters remain the most popular system for heating swimming pools. Today you can find new gas-fired heater models with much higher efficiencies than older models. Still, depending on your pool use, they may not be the most energy-efficient option when compared to heat pumps.

How They Work

Gas pool heaters use either natural gas or propane. As the pump circulates the pool’s water, the water drawn from the pool passes through a filter and then to the heater. The gas burns in the heater’s combustion chamber, generating heat that transfers to the water that’s returned to the pool.

Gas pool heaters are most efficient when heating pools for short periods of time, and they’re ideal for quickly heating pools. Gas pool heaters can be a good choice for pools that aren’t used on a regular basis. Unlike heat pumps, gas pool heaters can maintain any desired temperature regardless of how cold the weather gets.

Selecting a Gas Pool Heater

You should have a trained pool professional perform a proper sizing analysis for your specific swimming pool to determine pool heater size.

Sizing a gas or a heat pump pool heater involves many factors. Basically, a heater is sized according to the surface area of the pool and the difference between the pool and the average air temperatures. Other factors also affect the heating load for outdoor pools, such as wind exposure, humidity levels, and cool night temperatures. Pools located in areas with higher average wind speeds at the pool surface, lower humidity, and cool nights will require a larger heater.

Gas pool heaters are rated by Btu (British thermal unit) output. Outputs range from 75,000 Btu to 450,000 Btu.

Calculating Approximate Size

To calculate an approximate heater size for an outdoor swimming pool, follow these steps:

  1. Determine your desired swimming pool temperature;
  2. Determine the average temperature for the coldest month of pool use;
  3. Subtract the average temperature for the coldest month from the desired pool temperature. This will give you the temperature rise needed;
  4. Calculate the pool surface area in square feet;
  5. Use the following formula* to determine the Btu/hour output requirement of the heater: Pool Area x Temperature Rise x 12

Note: This formula is based on 1º to 1-1/4ºF temperature rise per hour and a 3-1/2 mile per hour average wind at the pool surface. For a 1-1/2ºF rise multiply by 1.5. For a 2ºF rise multiply by 2.0.

Installation and Maintenance

Proper installation and maintenance of your gas pool heater can optimize its efficiency. It’s best to have a qualified pool professional install the heater and perform complicated maintenance or repair tasks.

Read your owner’s manual for a maintenance schedule and/or recommendations. You’ll probably need to tune up your pool heater annually. Also, scaling in the burner or heat exchanger may decrease efficiency over a period of time.

With proper installation and maintenance, gas pool heaters typically last five or more years.

Following are links to both a heater sizing guide and heater ordering guide that you may find useful:

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