The buzz words today are all about saving costs and being ‘green’ or energy-efficient. With pool heaters, it is easy to go green. Older heaters, between seven and 10 years old, may have initially been approximately 78 percent efficient, but over time, they are now probably only 60 percent. This degradation typically occurs as heat exchanger tubes become clogged with build-up and burners become obstructed.
That said, now is the time to bring up the subject of replacing old heaters, especially with aquatic facility managers who experienced high energy costs the previous season. Replacing pool heaters is the perfect place to start in the effort to lower facility operating costs, allowing any savings to be re-invested into other pool upgrades.
Why new heaters make sense
Today’s heaters are designed for efficiency. In fact, most are up to 96 percent efficient and use fully condensing heater technology. They are also engineered to resist more corrosive pool environments, as corrosion has become a much bigger issue for aquatic facilities over the past five to seven years due to the exponential growth of on-site salt chlorine generators installed on pools. In response to this changing environment, heaters are now constructed with titanium direct-
fire heat exchangers, which have a higher resistance to corrosion.
Not only are these systems beneficial for aquatic facilities, they also come with the latest technology such as light-emitting diode (LED) panels which display error codes that can be extremely helpful to technicians who are troubleshooting and/or servicing them. In fact, some models enable technicians to use service apps installed on their smartphone to quickly troubleshoot any problems with the unit—even if the technician is not an expert on heaters.
Why do heaters become less efficient over time?
Depending on the unit, the efficiency of present-day pool heaters range between 85 to 96 percent ‘out of the box.’ Those rated 85 percent efficient with a 400,000 British thermal unit (BTU) input provide an output of 85 percent of the total BTUs. Therefore, in this case, it would be 340,000 BTUs that come out of the heater. Another way to look at it is an 85 percent efficient heater uses $85 to produce useful heat for every $100 of fuel. Essentially, the heater wastes 15 percent of the fuel.
Heaters between seven and 10 years old were approximately 78 percent efficient when new. Therefore, using the same example as above, a 400,000 BTU heater input actually produces only 280,000 BTUs of heat. This is assuming the heater is still operating at the same rate it did when it was first installed. That said, most heaters start losing efficiency over time just from basic operation. There are several other reasons for decreased efficiency, including:
Buildup on heat exchanger tubes
Heat exchanger tubes buildup with chemical residuals and calcium that causes the unit to lower its water flow. When flow is reduced, the unit loses its ability to heat the pool water which makes it less efficient than originally designed. This also causes the unit to consume more energy to heat the same amount of water in the pool.
Reduced water flow
When water flow is too fast, it results in condensation. If the water flow is too slow, the heater is not warming the water efficiently. Therefore, a pump that provides an irregular water flow can actually contribute to a heater’s inefficiency. If this is the case, this might be the right time for an aquatic facility manager to also look at installing a variable-frequency drive (VFD) to ensure the water flow through the heater remains consistent.
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. Carbon will adhere to the heat exchanger as a result of condensation. The condensate collects then drops onto the burners. The combustion is then compromised as ‘raining’ condensate interferes with the flame pattern. This poor combustion turns into ‘soot’ which collects on the fins and impedes the flue gasses. Not only will the condensation cause inefficiencies in the heater functionality, but 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 by causing build up that leads to the blockage of the heat exchanger.
Lack of proper ventilation
Lack of proper ventilation can cause ‘sooting’ which prevents the heater from operating at its maximum efficiency. The soot layer insulates the heat exchanger and greatly reduces its ability to transfer heat to the water.
Costs of reduced efficiency
To better understand the costs involved for an aquatic facility using a heater affected by reduced efficiencies, the following example is a calculation for a 75,708-L (20,000-gal) pool that requires a 20-degree temperature rise. (Note: one BTU will raise the temperature of 0.45 kg (1 lb) of water by one degree. Three-and-three-quarter liters (1 gal) of water weigh 3.77 kg (8.33 lb).
20,000 gal x 8.33 lb = 166,600 lb (amount of water in the pool that needs to be heated)
166,600 lb x 20 (temperature rise) = 3,332,000 BTUs required (BTUs is a measurement per hour)
Therefore, 3,332,000 BTUs are needed to raise the pool water temperature by 20 degrees or 138,833 BTUs per hour (3,332,000 / 24 hours = 138,833 output BTU per hour required)
The following is the same calculation, but instead using a new 400,000 BTU heater that is 85 percent efficient or, in other words, has a 340,000 BTU output. Using this heater, it will take 9.8 hours to raise the pool’s water temperature by 20 degrees.
3,332,000 BTUs / 340,000 = 9.8 hours
Gas companies charge by the cubic meter (2.77 m3) (which is equivalent to 100,000 BTUs); therefore, knowing it will take 9.8 hours to raise the pool water temperature, the cost can be calculated by multiplying the heat up time (hours) by the heater’s BTU input, then dividing by 100,000 and multiplying by the cost per cubic meter.
9.8 x 400,000 = 3,920,000 (total BTUs)
3,920,000 / 100,000 = 108.8 m3 used
Using the Ontario Energy Board’s online bill calculator, if the cost of gas is 17.9 cents/cubic meter (factoring in customer, delivery, supply charges, and taxes), the approximate cost would be $61.45.
(or $61.45 to raise the water temperature in a 75,708-L [20,000-gal] pool by 20 degrees in 9.8 hours)
Using a five- to seven-year-old 400,000 BTU heater that was rated 78 percent efficient, but is now only operating at 65 percent, the heater output would only be 260,000 BTUs.
3,332,000 BTUs required / 260,000 = 12.8 hours
12.8 x 400,000 = 5,120,000 BTUs
5,120,000 BTUs / 100,000 = 142.1 m3 used
Again, using the Ontario Energy Board’s online bill calculator, if the cost of gas is 17.9 cents/cubic meter (factoring in customer, delivery, supply charges, and taxes), the approximate cost would be $75.59.
This means it would cost the aquatic facility 23 percent more to heat the same body of water using an older heater.
|Five reasons to install a new heater|
|1. Lower energy costs as they have much higher efficiencies (between 85 and 96 percent) than older models (between 60 and 78 percent).|
|2. Smaller and take up less space.|
|3. Lower emissions, making them better for the environment.|
|4. Much easier to maintain (plug-and-play).|
|5. Quiet operation, reducing noise levels at commercial aquatic facilities.|
Choosing a heater for a commercial pool
To select the appropriate heater for a commercial pool, its size and location (indoor or outdoor) must be considered. To calculate the approximate heater size for a pool, facility managers need to:
- Determine the desired pool water temperature (the average is [27.7 C] 82 F for competitive swimming);
- Determine the average temperature for the coldest month of pool use (for outdoor facilities);
- Subtract the average temperature for the coldest month from the desired pool temperature. This will give the temperature rise needed;
- Calculate the pool surface area in square meters (square feet); and
- Determine the BTU/hour output required using the following formula: 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 one million BTU takes 24 hours to raise the pool water temperature 15 degrees. Based on this information, a facility manager can determine which heater is appropriate for the commercial pool he/she operates.
Additional benefits of a heater upgrade
In addition to lowering operating costs, there are additional benefits to upgrading aquatic facilities with a new heater.
1. Lower emissions
Newer heaters are cleaner burning (i.e. low NOx) which have minimal emissions. These units are friendlier to the environment as the nitrous oxide emissions are below 10 percent.
2. Easier maintenance (plug-and-play)
Today’s commercial pool heaters face changing conditions as many installers have not been trained in commercial application techniques. Further, facilities find pool cleaning staff, lifeguards, and facility managers are all adjusting heater settings frequently. Therefore, having a unit that is completely enclosed and ready to go leaves less room for problems. Heaters are constantly faced with:
- Improper control of return water temperature which results in the heat exchanger condensing and failing;
- Insufficient combustion air and chemicals which attack the heat exchanger and chamber; and
- Changes in flow rates as a result of dirty filters, human error when backwashing, and/or improper settings on bypass valves.
3. Sealed combustion
Many new heaters have sealed combustion units, which are safer because:
- Units installed indoors are frequently located next to stored chemicals; therefore, a sealed combustion unit is less of a fire hazard; and
- Adequate combustion air is guaranteed when outside air is ducted with a sealed combustion unit.
Venting requirements for new heaters are quite different than what was done in the past. Although this process has become easier, the importance of proper venting has never been more critical. These products must be installed and serviced by a professional service technician, qualified in pool heater installation, to ensure the work is performed correctly.
Aquatic facility managers should check with their local building authority about contractor licensing requirements when performing a heater upgrade.
Improper installation and/or operation could result in insufficient venting of carbon monoxide (CO) gas and/or flue gases which could cause serious injury. Improperly installing or venting a heater will also void a manufacturer’s warranty.
|Heater installation tip|
|One of the more common mistakes that occur when installing a new heater is to upgrade the size of the unit without having a large enough supply of gas. For example, if the facility had a gas line for a 200,000 BTU heater and the new unit is a 400,000 BTU rated heater, the gas line also needs to be increased in size to accommodate the increased output.|
When venting heaters, it is important to maintain proper clearances from combustible surfaces which are, in most cases, 152 mm (6 in.) on the sides and top of the heater. When considering requirements with respect to how far a heater can be vented or how far ductwork can run to pull intake air, it should be noted each 90-degree elbow reduces the maximum horizontal polyvinyl chloride (PVC) air intake duct run by 3.6 m (12 ft). Each 45-degree elbow reduces the maximum run by 1.8 m (6 ft). These are critical notes when it comes to proper heater installation and efficiencies.
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 305 mm (12 in.) of the ceiling; and the other within 305 mm (12 in.) of the floor for combustion air. This installation procedure is in accordance with American National Standards Institute (ANSI) Z223.1, National Fuel Gas Code, CSA B149.1, Natural Gas and Propane Installation Codes, as applicable, and any local codes that may apply. These openings shall directly, or through a duct, connect to outdoor air.
For indoor installations, the heater is tested for a direct air intake duct using 102 mm (4 in.) PVC pipe. Exhaust vent pipes must not be combined to a common exhaust vent in multiple unit installations. Separate vent pipes must be installed. In the past, venting and air intakes had to be balanced and be the same length; however, this is not the case for newer heaters, as they draw combustible air from outside the structure and flue gasses are forced out.
The color of the heater’s flame is a good indication of whether or not the unit is receiving enough combustible air to function properly. A good flame burns blue and clear, which is a sign that it is burning 100 percent of the gas. If the flame is not getting enough air, it becomes orange and releases carbon, which turns to soot and clogs the heat exchangers.
Smaller size, easier installation
|How pool heaters work|
|The pump draws water from the pool and circulates it through the 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, heat from the copper tubes is conducted to the water, increasing the temperature.
The water then returns to the pool and re-circulates for consistent heating. This simple process provides quick, controlled heat.
Heaters have also become smaller and more lightweight and, as a result, a unit can be installed by one person. This also enables a team of service technicians to be more profitable as more jobs can be completed. In the past, two technicians were always required as heaters were much larger and heavier.
Smaller units also take up less space which provides more room for venting (for indoor installations), while those installed outdoors are more aesthetically pleasing because of their compact size and lower profile.
Recognizing what it means for a pool heater to be ‘efficient’ and knowing why a unit has become inefficient are the first steps to understanding the benefits of upgrading a pool with a new green heater. These units will not only lower a facility’s operating costs immediately but will also provide additional benefits to the facility and the technicians who service the pool.
This article was written by Mike Fowler and originally appeared on Pool & Spa Marketing [link].