A look at the evolution of pool heater technology

Igniting change

Some pool heater innovations came about for reasons that have nothing to do with regulations or standards. Rather, some modifications simply make the product safer or easier to use.

The earliest generations of gas-fired pool heaters used either push-button pilot flame ignition, which is still used on some domestic tank water heaters, or millivolt type ignition, which is similar to the push-button spark switches commonly found on gas barbecues.

Before the advent of electronic ignition and digital controls for pool heaters, homeowners had to manually ignite their heaters during initial start-up, or if the pilot light went out for some reason. Constant burning of the pilot flame used unnecessary gas and resulted in higher energy costs for the consumer.

Constantly burning pilot flames work for residential water heaters because the demand for hot water comes when the water in the tank cools to a certain level (not to mention the tank holds approximately 150 L [40 gal] as opposed to a 38,000-L [10,000-gal] pool). When the temperature of the water in a residential water tank drops to a preset level, a gas valve opens and the heater fires up to heat the water. This technology works for a residential water heater, but not for a pool heater.

Today, gas pool heaters use direct spark ignition (DSI) or hot surface ignition (HSI). Both are forms of electronic igniters. DSI provides fast ignition and solid construction; however, it also requires a high voltage spark generator. Spark intensity can be affected by deposits formed on the igniter; therefore, heaters designed with this type of ignition system must also have a separate flame sensing rod.

On the other hand, HSI combines the igniter and flame sensor into one unit, so there is no need for a spark generator. This brings the cost of the ignition system down and provides reliable performance. The downsides to this type of equipment is the igniter is fragile, so care must be taken when it is being serviced or handled, not to mention it can crack over time.

The move to electronic ignition provides a more reliable and safer ignition process as timing is more precise and the excess build-up of natural or propane gas in the heater prior to ignition is eliminated.

In control

Changes in pool heater ignition stemmed from the development of electronic circuit boards and the move to digital technology in the ’80s. Digital controls became the norm in virtually every category of consumer and industrial project, pool heaters were no different. In addition to bringing about changes in ignition, the digital technology revolution that started during this period led to great improvements in pool heater controls, which were brought to market in the early ’90s. This included digital temperature displays and controls on top of the heater which could be rotated to face any direction. Therefore, no matter how the heater is positioned on the equipment pad, the controls can be rotated so they can be conveniently read and adjusted.

This feature can still be found on some of today’s units. In fact, almost all models have digital displays that show real-time water temperature, making adjustments more precise than simply pushing an up or down button for temperature control. Digital displays also allow for advanced settings, troubleshooting, and error display. This is not only convenient for homeowners, but also for service professionals and installers.