Swimming Pool Blog
by Sean Griffin, April 12, 2010
Gas Pool Heater Troubleshooting ~ Gas+Water+Electricity
The heater in your backyard warming- up the spa or maintaining your pool water temperature is a complex piece of equipment. Whether you run your heater year-round or winterize your unit and are just trying to start up for the season, some common problems may arise. Every heater brand is unique and a troubleshooting guide is included in the manual and is sometimes even offered on the manufacturers’ web-site. All heaters have the potential to be hazardous and proper precautions should be taken. Electricity, gas, and water all converge to make it possible to operate so a qualified professional should be brought in if you are not comfortable working with these elements.
Modern heaters are equipped with a digital display and self diagnostics to help determine the reason your heater isn’t firing or coming up to the desired temperature. Some units call for manual service to diagnose and an outline for troubleshooting should be obtained for a step by step guide for diagnosing and repairing. As mentioned previously, there are three elements combining at the heater and all are monitored by the heater through a serious of safety devices.
Gas pool heaters require a power source, and the "problem lies where the power dies". First determine that proper power is reaching the unit. From the power source, voltage runs into a transformer within the heater where 110 or 220 volts are "stepped down" or transformed to a lower voltage, usually 24-28 volts. From the transformer, power runs into the IID, or control module. Proper millivolt levels are required to open the gas valve, run the control board, spark the pilot, and run the internal safety loop - allowing the heater to “fire”. Technical support from the manufacturer can be used when testing electrical components. Check all electrical connections to confirm all contacts are good. In some cases I have found that terminals and leads on wiring needs to be cleaned with a wire brush to remove corrosion and rust. Make sure that rodents have not taken up winter residence inside your heater and chewed on any wires. Bypassing certain components can be used to diagnose but should not be done to operate the unit. Replace any component that is malfunctioning and correct the reason for failure.
Gas pool heaters require either Liquid Propane or Natural Gas to run the unit. Gas lines from the source (meter or tank) run to a regulator outside of the heater. From the regulator, gas pipe is connected to the internal gas valve on the heater. Gas is distributed through a burner manifold and orifices and out to burner tray which is ignited by the pilot. An even flame across the burner tray below the heat exchanger transfers heat to the water as it moves through the individual tubes of the tube bundle (finned heat exchanger). Proper gas pressure is required to operate a heater. If you are opening up for the start of season make sure both external and internal valves are open. You may need to manually assist pilot with controls on valve inside your unit. Typically step by step instructions are printed within the unit, usually a label on the door. A manometer can be used to determine gas pressure both on the intake and the output of the internal gas valve. Confirm that your gas pilot tubing is intact and allow for adequate time to bleed any tubing if you need to assist pilot. Sometimes, small (tiny!) red spiders or mud daubers can clog the pilot orifice. If no gas is flowing to the pilot, you may have a broken or clogged pilot tube or pilot orifice.
Gas pool heaters have a flow sensor or a pressure switch which makes sure that adequate water is moving through the heat exchanger before allowing the gas valve to open. A very common reason a heater will not fire is simply because the system pressure is either too high or too low. A simple and necessary fix is to attend to equipment operation. Basically, clean the filter and pump baskets - and make sure that there is no external heater bypass, allowing too much water to flow past the heater. There also is an Internal Bypass inside the front header. If this becomes stuck open, or broken, it may allow too much water to bypass the heat exchanger. If the heater will not fire, and flow and pressure are within proper parameters, the pressure switch may need to be replaced. "Jumping Out" the pressure switch with a small jumper wire will confirm if the switch is preventing the heater from firing.
Proper water chemistry will prevent corrosive or scaling conditions within the heat exchangers. The heat exchanger is where heat is transferred from flame to the water. Corrosive water chemistry can lead to leaks which will lead to water loss and also damaging other components of the heater. Keeping the pool pH in proper range is important, and if you use a chlorinator, make sure that it is installed as far after the heater as possible. Chlorinators installed before the heater, or offline chlorinators installed backwards will ruin a very expensive heat exchanger in no time, while depositing ugly blue/green stains on pool plaster.
For your pool heater to work properly you will have to have everything in order. Proper electrical components, proper gas pressure with functioning valving, and adequate water flow. Working with these components can be hazardous, use caution when lighting a heater, as "flame roll-out" is common. Propane gas tends to "puddle" as it is heavier than air, so be sure to follow the manufacturer recommended safety precautions when lighting or diagnosing your gas pool heater.
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More Pool Heater Technical Pages
What Size Pool Heater Do I Need?
What's the Difference in Millivolt Heaters vs. Electronic Heaters?
Visit the Pool Janitor's Heater Page for technical information
Energy Facts on Gas Pool Heater usage