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Ensure Long Heater Life

By Mike Fowler


When it comes to looking at the common causes of pool heater failure, many are linked to improper installation. Therefore, pool professionals that want to be sure pool water stays warm when pools are first opened this spring and into summer (in case of a cool summer), should take the time to review the heater installation for each of the pools they maintain.

Proper Heater Sizing

It is vital for the heater, along with other components in the equipment room, to be sized correctly for the facility's pool along with any additional bodies of water that might be connected. This includes spas and splash play areas. To size the equipment properly, the specifications for the heater should be consulted to compare them to the flow rate that will be pumped through the unit.

To calculate an approximate heater size for a pool, technicians must:

  • Determine the desired pool water temperature (average is 82 degrees F for competitive swimming).
  • Determine the average temperature for the coldest month the pool will be used (if it is an outdoor pool).
  • Subtract the average temperature for the coldest month from the desired pool water temperature. This will provide the temperature rise needed.
  • Calculate the pool surface area in square feet.
  • To determine the British thermal unit (Btu) output needed for gas pool heaters, the formula is calculated by multiplying the pool area (in square feet) by the temperature rise (ideal water temperature/average temperature in coldest month) by 12.

To clarify, heaters are sized based on a 24-hour temperature rise. Therefore, a heater with one million Btus takes 24 hours to raise the pool temperature 15 degrees for a 5,450 square foot pool. Based on this information, the appropriate heater can be selected for the pool.

If the heater does not appear to be sized properly, it should be replaced. In fact, replacing older heaters with new, energy-efficient units will not only provide improved water heating but will also reduce energy consumption and lower operating costs in the process.

Gas Meter Sizing

Just as it is important for the heater to be sized properly, it is also important the gas meter is sized appropriately for the heater. Assuming the pool heater is using natural gas, the meter must be sized—at minimum—to the capacity of the heater itself. In other words, if one is using a 400,000 Btu heater, the meter should be capable of providing 400,000 Btus. Always remember that there may be other items pulling gas from that same meter so must be calculated in when making sure the gas meter is properly sized. Low gas pressure can cause damage to the internal components of a heater, causing build-up that leads to blockage of the heat exchanger.

Propane Tank

If the pool heater is propane-fuelled, the tank must be large enough to supply the proper amount of gas to the heater. Improper gas pressures to the heater—while in operation—will cause lower efficiencies in the heater and possibly a buildup of soot, which could cause damage to the burners, as well as the heat exchanger.

Gas Line & Venting

Once again, sizing is very important. The gas line to the heater, as well as the venting of the heater, need to be sized and vented properly.

When venting heaters, it is important to maintain proper clearances 6 inches from combustible surfaces on the top and side of the unit. Check the heater manufacturer's manual for recommended clearances.

When considering requirements with respect to how far a heater can be vented, or how far ductwork can run to pull intake air, each 90-degree elbow reduces the maximum horizontal polyvinyl chloride (PVC) air intake run by 12 feet. Each 45-degree elbow reduces the maximum run by 6 feet.

The minimum requirements for air supply specify the room in which a heater is installed to be equipped with two permanent air supply openings: one within 12 inches of the ceiling and the other within 12 inches of the floor for combustion air. This installation procedure is in accordance with the American National Standards Institute (ANSI) Z223.1, National Fuel Gas code, as applicable, and any local codes that may apply.

Air supply openings should directly, or through a duct, connect to outdoor air. In the past, venting and air intake ducts had to be in balance and be the same length; however, with newer heaters, they draw combustible air from outside the structure and flue gases are forced out.

The color of the heater's flame is a good indicator of whether or not the unit is receiving enough combustible air to function properly. A clear, blue flame indicates the unit is burning 100 per cent of the gas. If the flame is not getting enough air, it becomes orange and releases carbon that turns to soot and clogs heat exchangers.

One of the more common mistakes that occur when installing a new heater is upgrading the size of the unit without having a large enough gas supply. For example, if the pool previously had a gas line for a 200,000 Btu heater and the new unit is rated 400,000 Btus, the gas line also needs to be bigger to accommodate the increased output.