A look at the evolution of pool heater technology

Sometimes, rules rule

Increasing thermal efficiency, while maintaining manageability and affordability, is an ongoing effort that is occasionally driven, for better or worse, by government regulations.

About the same time the first pool heater to achieve thermal efficiency above 90 per cent came to market, Santa Barbara County in California implemented a rule requiring all heaters use condensing technology and be rated no less than 93 per cent thermal efficiency. This local regulation did not stay on the books for long (perhaps, at least in part, because these heaters were, at the time, much more expensive than other products available on the market), but it did set a goal for product development teams across the industry.

Current regulations in some parts of the United States prevent use of electric resistance pool heaters (e.g. California Energy Commission’s [CEC’s] Title 20 and 24 Appliance Efficiency Regulations) due to the high cost of electric energy.

Another category of rules that have influenced some heater design changes came out of the South Coast Air Quality Management District (SCAQMD). Formed in 1976, SCAQMD is the air pollution agency responsible for regulating stationary sources of air pollution (that is, fixed appliances, not cars or trucks) in parts of Southern California. Other parts of North America typically look to California and SCAQMD, in particular, as precursors to regulations in other areas. For instance, Natural Resources Canada’s ‘ecoENERGY Efficiency for Equipment Standards and Labelling’ programs have historically paved the way for the introduction of new and more stringent standards, which are closely aligned with U.S. developments.

In 1998, SCAQMD adopted a rule requiring water heaters and boilers with rated heat capacities up to two million BTUs to limit NOx emissions. (NOx emissions are the sum of nitrogen oxide and nitrogen dioxide in the flue gas, collectively expressed as nitrogen dioxide.) Any heater sold in areas of Southern California governed by SCAQMD had to meet the emissions limits. These regulations went into effect on Jan. 1, 2000. Parts of Texas implemented similar rules around the same time.

Anticipating the spread of these rules, some pool heater manufacturers developed new products or modified existing ones to comply with the low NOx emission standards. By the time the new rules were announced (in the ’90s), only one heater, Max-E-Therm,® then manufactured by Sta-Rite, met the low NOx requirements without requiring any modifications as it used pre-mixed gas technology with a forced-air ignition. Low NOx emissions requirements were influential in bringing about a new class of pool heaters 15 years ago.

A good mix

Pre-mixed gas and forced-air ignition technology was used in other industries, such as domestic and commercial hot water heaters and boilers, before finding its way into the pool industry. Early on, gas heaters required natural air-draft to create sufficient air-gas mixture for ignition. For this reason, the industry refers to these as atmospheric or natural draft heaters. These products are still available, but as of April 2013 the U.S. government requires these heaters to be a minimum of 82 per cent thermal efficiency. As a result, this renders most atmospheric heaters obsolete as they can only manage, at best, approximately 60 to 78 per cent thermal efficiency.

Also in 2013, Environment Canada’s Target 2.1: Outdoor Air Pollutants program was implemented to improve outdoor air quality by ensuring compliance with new or amended regulated emission limits by 2020, and thus reducing emissions of air pollutants in support of the Air Quality Management System (AQMS) objectives of the Federal Sustainable Development Strategy 2013-2016.

Atmospheric pool heaters were typically larger in size and heavier because they had to accommodate multiple burners and their heat exchangers took up a lot of space. Further, to operate these heaters indoors, sufficient air draft/supply had to be provided.

Perhaps the most significant reason for the shift away from using atmospheric heaters was the advent of new technology using forced-air blowers and pre-mixed gas (PMG). This technology enables heaters to draw outside air directly into the unit through a simple PVC pipe connection. This is especially useful with indoor installations where heaters are located in basements and small boiler rooms where ventilation would be insufficient for atmospheric heaters.

Heaters using forced air and PMG technology also burn fuel cleaner, thus reducing emissions. Knowing this, it is easy to see why the industry is moving away from atmospheric heaters, at least in part, because they typically had to be installed outdoors to have sufficient air-draft.

Product innovations and a change in standards weighed heavily on heater evolution—especially with the introduction of low NOx emission standards. For example, Chapter 5, section 7.2 of the CEC’s Water Heating Requirements mandate before any pool or spa heating system or equipment may be installed, the manufacturer must certify to the Energy Commission the system or equipment complies with:

• 110.4—heated pools are equipped with a cover; and
• 110.5­—pool and spa heaters may not have continuously burning pilot lights.

The latter has become a non-issue (and an easy regulation to comply with) as continuous pilot lights have not been used in the manufacturing of pool heaters since prior to the ’80s. In fact, they were being phased out even earlier. This was primarily because they wasted gas, and pilot-burning appliances consume more energy.

The CEC also requires:

• A minimum heating efficiency according to Appliance Efficiency Regulations;
• An on-off switch outside the heater;
• Permanent and weatherproof operating instructions; and
• No electric resistance heating.

The CEC does not allow electric resistance heating because it is extremely inefficient and expensive. As a result, this technology is no longer used for heating pools. Looking at product evolution in the context of related regulations is always interesting. In some cases, new regulations dictate or accelerate product development. In other cases, a new product or feature comes to market and a legislator or code writer—from local municipalities up to national and even international regulating bodies—learns about it, determines that it could solve a problem, and moves forward to propose and advocate regulations requiring its use.