A typical troubleshooting scenario
This process should be similar for most gas pool heaters, although some of the particular details may differ depending on the manufacturer.
If the heater will not fire, start with the sources: gas and electricity. Make sure the gas supply valve is open as to avoid restricting gas flow and the heater’s gas valve is in the ‘on’ position. Also, inspect the wiring and connections to make sure the wiring harness is properly connected.
If these things check out, move onto the real troubleshooting. The first thing to inspect is gas pressure. This can be done using a manometer to measure the static gas pressure. This is the reading before the heater is fired. Next, turn the heater on, wait roughly 20 seconds and then take note of the gas pressure (after the gas valve clicks). Once the gas valve is open, the heater should run between 0.996 and 3.49 kPa (4 and 14 in. water column [WC]). A 0.498-kPa (2-in. WC) drop from static to running is normal. If the heater’s static pressure is at 1.992 kPa (8 in. WC) and drops below 0.996 kPa (4 in. WC), verify the size of the gas line and meter. A heater that starts at 203.2 mm (8 in. WC) and drops to 101.6 mm (4 in. WC), even if it is in the range, may have a supply problem. Should another gas appliance be turned on in the home, it may be enough to shut down the heater.
The heater will shut down after seven seconds if it does not ignite the gas. If the gas valve does not click open, test for 24 volts at the gas valve. If voltage is found, replace the gas valve. If no voltage is found, inspect the wiring between the gas valve and the board. If the gas valve clicks open and the smell of unburned gas is detected, the hot surface ignitor may be defective (more on this later). If the ignitor test shows it is functioning properly, verify there is nothing interfering with the ignitor (e.g. insulation). Remove the ignitor and inspect the opening. If it is clear, check all the ground connections because the hot surface ignitor senses the flame through the ground.
Be sure to check the ground connections to the ignition control module and the control board as well. On some rare occasions, the ground pins on the ignition control module or control board could be defective, interrupting the ground. Therefore, replace them if necessary.
While some troubleshooting steps are different from one manufacturer’s heater to another, there are three main components on today’s gas pool heaters that are more or less universal: the transformer, the hot surface ignitor, and the thermistor.
The transformer
Most transformers used in swimming pool heaters are step-down transformers. This means they take high voltage (usually 120 or 240 volts) and transform it to 24 volts, which is usually used by the heater’s circuit boards and its safety components. To ensure the transformer is working correctly, use a voltmeter to check the incoming voltage to the primary side (high voltage) of the transformer. Depending on the transformer, there may be two or three wires on the primary side. Place a lead on one wire and the other lead on one of the remaining wires, and then read the voltmeter for the incoming voltage. If no voltage is present, move the lead to the remaining wire. If no voltage is present, the transformer is not the problem; however, it may be in the wiring to the transformer. If voltage is present, check voltage on the secondary side of the transformer. To do this, place one lead on one wire and the other lead on the remaining wire. If voltage is not present on the secondary side, but was present on the primary side, the transformer is defective. If voltage is present, the transformer is good and other potential problems should be investigated further. Check the wiring from the transformer to the board. It could be loose or damaged. If the wiring and connectors are okay, the board is likely the problem.
