If your gas boiler is not firing up despite the pilot being lit, there could be several potential reasons behind this issue. This comprehensive guide will walk you through the common causes and provide step-by-step troubleshooting instructions to help you get your gas boiler back up and running.
Dirty Flame Scanner
One of the most common reasons for a gas boiler not firing up is a dirty flame scanner. The flame scanner is a safety device that monitors the pilot flame and ensures the gas valve remains open only when the pilot is lit. If the flame scanner lens is dirty or obstructed, it can prevent the boiler from igniting.
Troubleshooting Steps
- Inspect the Flame Scanner Lens: Regularly inspect the flame scanner lens, at least once a month, and clean it if necessary. Use a soft, lint-free cloth to gently wipe away any dust or debris.
- Check the Flame Signal Voltage: Locate the flame safeguard control display screen and check the flame signal voltage. The voltage should typically be between 1.5 to 4.5 VDC for proper operation. If the signal is weak, below 1.5 VDC, clean the lens or service the pilot assembly.
- Clean the Pilot Assembly: If the flame signal is weak, you may need to clean the pilot assembly. Carefully remove any soot or debris from the pilot orifice and the surrounding area.
Cracked or Broken Electrode
Another common issue that can prevent a gas boiler from firing up is a cracked or broken pilot electrode. The pilot electrode is responsible for igniting the pilot flame, and if it’s damaged, the boiler won’t be able to light.
Troubleshooting Steps
- Inspect the Pilot Assembly: Inspect the pilot assembly every three months and replace the electrodes annually as a preventative measure.
- Listen for Ticking or Clicking: If you hear a ticking or clicking noise coming from the pilot assembly, it’s a sign that the electrode is cracked or broken.
- Replace the Electrode: If the electrode is damaged, replace it with a new one. Ensure the replacement electrode is compatible with your specific boiler model.
Faulty Pilot Ignition Cable
The pilot ignition cable is responsible for delivering the electrical signal from the control board to the pilot electrode. If the cable is damaged or corroded, it can prevent the pilot from igniting.
Troubleshooting Steps
- Inspect the Ignition Cable: Visually inspect the pilot ignition cable for any signs of damage, such as cracks, fraying, or corrosion.
- Check the Electrical Connection: Ensure the ignition cable is properly connected to both the control board and the pilot electrode.
- Test the Cable: If the cable appears to be in good condition, you can use a multimeter to test the continuity of the cable. Replace the cable if it’s faulty.
Faulty Gas Valve or Pilot Valve
The gas valve and pilot valve are responsible for regulating the flow of gas to the boiler. If either of these valves is malfunctioning, it can prevent the boiler from firing up.
Troubleshooting Steps
- Check the Manual Gas Valve: Verify that the manual gas valve is fully open, allowing gas to reach the boiler.
- Inspect the Gas Valve: Examine the gas valve for any signs of blockages, seized parts, or damaged electrical components. If the valve appears to be malfunctioning, it may need to be serviced or replaced by a qualified technician.
- Ensure Proper Regulation: Make sure the gas valve is properly regulated and serviced by an authorized professional to ensure it’s functioning correctly.
Other Potential Issues
In addition to the above common causes, there are a few other factors that could prevent your gas boiler from firing up:
- Loose Wires or Connections: Check all electrical connections and wiring for any loose or damaged components.
- Thermostat Malfunction: Ensure the thermostat is functioning correctly and calling for heat.
- Circulator Pump Issues: Verify that the circulator pumps are running and the boiler is receiving power.
Troubleshooting Steps
- Check the Basics: Start by ensuring the pilot is lit and the manual gas valve is open. Also, verify that the thermostat is calling for heat.
- Inspect the Pilot Assembly: Examine the pilot electrode and ignition cable for any signs of damage or corrosion. Clean or replace the electrode if necessary.
- Check the Gas Valve: Ensure the gas valve is open and not blocked. Look for any signs of damage or malfunction.
- Consult a Professional: If none of the above steps resolve the issue, it’s best to call a gas-safe engineer for further assistance.
Technical Specifications
Flame Scanner
- Operates via UV, visible, or infrared light signaling.
- Requires regular cleaning and inspection to maintain optimal performance.
- Typical flame signal voltage range: 1.5 to 4.5 VDC.
Pilot Electrode
- Should be inspected and replaced annually as a preventative measure.
- A cracked or broken electrode will prevent the boiler from igniting.
Gas Valve
- Regulates the flow of gas to the boiler.
- Requires regular maintenance and inspection by a qualified professional to ensure proper function.
References
- Heatable. (n.d.). Boiler Not Working? Find out Why and How to Fix it. Retrieved from https://heatable.co.uk/boiler-advice/boiler-not-working
- LAVIMONIERE PRODUCTIONS, LLC. (2017, December 13). Gas Boiler/ pilot on, but will not fire. YouTube. Retrieved from https://www.youtube.com/watch?v=PH_QOVgla0U
- (2019, December 14). gas boiler will not fire. YouTube. Retrieved from https://www.youtube.com/watch?v=JIGOlOPCuqg
- HeatingNY. (2021, February 10). Five Reasons Your Gas Boiler Fails on Ignition. Retrieved from https://heatingny.com/2021/02/10/five-reasons-your-boiler-fails-on-ignition/
- HeatingHelp. (2023, July 27). Call for heat: circulator running, boiler not firing (pilot lit). Retrieved from https://forum.heatinghelp.com/discussion/192956/call-for-heat-circulator-running-boiler-not-firing-pilot-lit