Simply stated, the only job of the heater is to heat the water to the desired temperature. A heater is not required equipment. Rather, the heater is a luxury item to make the water temperature more comfortable. The gas-powered heaters are still the most popular pool heaters.
There are two types of gas-powered heaters:
- natural gas heaters
- propane heaters
Regardless of the gas source (natural gas or propane), an ignition device, which is an internal technology, is required to start the overall heating process. There are two types of ignition devices in any gas-powered heater:
- millivolt ignition
- electronic ignition natural gas heaters
The main (on-the-surface) difference between these two types of ignition devices is that the pilot light continuously remains lit on a millivolt ignition heater and the pilot light only lights when needed on an electronic ignition heater. There are other technical and internal differences between these two ignition devices.
Generally speaking, when there is a call for heat (or in other words, when you want to use your heater), the heater burns gas (natural gas or propane) to generate and then transfer heat to the pool water. The ignition device starts the process of allowing the gas-powered heater to heat the pool water. The process of starting the heat cycle to actually heating the water is confusing, but it is made much easier - in fact, very simple - to understand in the various gas-powered heater categories of our Pool Manual.
If you have a gas-powered heater with millivolt ignition, it is recommended to upgrade to a heater with electronic ignition. The cost of the heaters is minimal, but the monthly savings can be significant. If you do have a heater with millivolt ignition and do upgrade to a heater with electronic ignition, you will need to hire a LICENSED ELECTRICIAN to wire a breaker for the new heater.
You can read the Pool Manual for additional information about gas-powered heaters and the various ignition devices and technologies.