Beat the Heater
Upgrading Aquatic Facility Heaters to Reduce Costs

By Mike Fowler

As energy costs continue to rise and facility managers look for ways to reduce their operating expenses, remember to look at your aquatic heater. Whether bidding on a complete renovation or simply looking for ways to reduce operating expenses, look at your pool and spa water heaters and the utility bills associated with their operation.

The buzzwords these days are all about saving costs and being "green" or energy efficient. And with heaters, it's a no-brainer. The older heaters of seven to 10 years ago might have started out being about 78 percent efficient. But those same heaters are probably now only about 60 percent efficient—as heat exchanger tubes fill with buildup and even the burners get clogged.

Just before winter is the perfect time to bring up the subject of upgrading those old heaters. Upgrading a heater is an easy way to lower heating bills.

Why New Heaters Make Sense

It is probably best to start by explaining how your aquatic facility heaters work and why heaters become less efficient over time.

It's important to understand that the pool pump circulates the pool's water, which is drawn from the pool then passes through a filter and into the heater. The heater's combustion chamber ignites the gas, heating copper tubes arranged above the burner tray. As the water passes through, the heat from these copper tubes is conducted to the water, increasing the water temperature. The water then returns to the pool and re-circulates for consistent heating. This simple process provides quick, controlled heat.

Here are some reasons to consider upgrading to a new heater:

  1. New heater models have much higher efficiencies (85 to 90 percent) than older models, and use less energy (new heaters will immediately lower energy bills).
  2. The heater you currently have is most likely not operating anywhere near its original efficiency rating.
  3. New heaters are smaller and take up less space.
  4. New heater models have lower emissions today than years ago—for better air quality and better environment.
  5. New heaters are easier to maintain (plug and play).

Gas pool heaters are rated by BTU input output (BTU stands for British thermal unit). Input outputs range from 75,000 Btu to 4,500,000 Btu. Today's swimming pool heaters start off being 85 to 90 percent efficient. This means that if you have a heater that is rated 85 percent efficient with a 400,000 BTU input, what comes out of the heater (output) or actual heating capability is 85 percent of the total BTU—so in this case, it would be 340,000 BTUs that come out of the heater.

Heaters that are seven to 10 years old started off being about 78 percent efficient. So, with the same example above, with a heater input of 400,000 BTUs you only receive an output of 280,000 BTUs. This is assuming the heater is still operating at the same rate as it did when it was first installed. However, most heaters start losing efficiency over time just from basic operation.

Reasons for Decreased Efficiency

Why are heaters not as efficient as when they were first installed? Here are a few reasons for decreased efficiency:

  • Buildup on heat exchanger tubes: Heat exchanger tubes build up with chemical residuals and calcium that cause the unit to lower its water flow. When the flow is reduced then the heater loses its ability to heat the water, making it less efficient than originally designed. This causes the unit to require more energy consumption to heat the same amount of water in the pool.
  • Reduced water flow: It's all about water flow. If the water flow is too fast, you get condensation. If the water flow is too slow, the heater is not warming the water efficiently. Note: A pump that isn't working properly can contribute to a heater's inefficiency due to irregular water flow. This might be an opportunity to also look at a variable frequency drive to ensure the water flow through the heater remains consistent.
  • Condensation: Propane and natural gas, when burned, produce water as a byproduct. If the heat exchanger is too "cool," the humid flue gases will condense on the fins of the heater. Condensation on the heat exchanger causes the carbon to adhere to the heat exchanger. The condensate collects then drops on to the burners. The combustion is then compromised as "raining" condensate that interferes with the flame pattern. This poor combustion turns into "soot," which collects on the fins, causing the flue gasses to be impeded. Not only will the condensation cause inefficiencies in the heater functionality, but it will also cause oxidation on copper from low return water temperatures.
  • Low gas pressure: Low gas pressure can cause damage to the internal parts of the heater causing buildup that leads to blocking of the heat exchanger.
  • Lack of proper ventilation: Can cause what is called "sooting" and thus not allow the heater to work to its maximum efficiencies. The soot layer is like insulating the heat exchanger, and heat does not transfer to the water as well.

Choosing a Heater

If you are now faced with a heater that is not operating efficiently and has caused your energy consumption to increase drastically for a reduced output, how do you choose a new heater?

It is important to realize that pool size does matter—as do factors such as whether or not the pool is an indoor or outdoor pool.

To calculate an approximate heater size for a pool:

  1. Determine the desired swimming pool temperature (average is 82 degrees for competitive swimming).
  2. Determine the average temperature for the coldest month of pool use (if the pool is an outdoor pool).
  3. Subtract the average temperature for the coldest month from the desired pool temperature. This will give the temperature rise needed.
  4. Calculate the pool surface area in square feet.
  5. Use the following formula provided by the U.S. Department of Energy:

    Pool area x Temperature Rise x 12 = the btu/ hour output required

To clarify, heaters are sized based on a 24-hour temperature rise. So a heater with a 1 million BTU takes 24 hours to raise the pool temperature 15 degrees.

Additional Benefits

Here are a few additional reasons to upgrade to a new heater:

  • Lower Emissions: Now there are cleaner burning heaters or Low NOx heaters, which have minimal emissions. In most of California, as well as Texas, these are required and have a regulated emission standard. Other states are sure to follow in the coming years.
  • Easier Maintenance: Today's commercial pool heaters face changing conditions as many installers have not been trained in commercial application techniques. Plus, facilities find that pool cleaning staff, lifeguards and facility managers are all adjusting heater settings frequently. So, having a unit that is completely enclosed and ready to go leaves less room for problems caused by facility staff.
  • Sealed Combustion: Many new heaters today have sealed combustion units. These are safer because: Pool heaters installed indoors are frequently located next to stored chemicals—so if they are sealed they are less of a fire hazard (even if chemicals are not present when heater is installed, chemicals maybe present later; and adequate combustion air is guaranteed when outside air is ducted with a sealed combustion unit.

Now you have all the facts for considering an upgrade to a newer, more efficient heater that will immediately reduce your energy bills and monthly operating costs. A new heater upgrade will surely lower an aquatic facility's monthly operating costs, will operate and output improved heated water and will be better for the environment as well.

Mike Fowler is the commercial marketing and sales manager for Pentair Aquatic Systems in Sanford, N.C. He has been with Pentair since 1992, starting his career in the technical services department at Purex Pool Products. Fowler has held many managerial roles within the company, including marketing, accounting and products. For more information, visit

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