The gas boiler pilot light not staying on is a common issue that can be caused by several factors, ranging from faulty thermocouples to clogged flex tubes. This comprehensive guide will delve into the most common reasons for this problem and provide detailed solutions to help you get your gas boiler back up and running efficiently.
Faulty or Dirty Thermocouple
The thermocouple is a critical safety device that detects the presence of the pilot light and shuts off the gas supply if the flame goes out. If the thermocouple is faulty, dirty, or misaligned, it can prevent the pilot light from staying lit.
Cause: A faulty or dirty thermocouple can disrupt the gas supply to the pilot light, causing it to extinguish.
Solution: Clean the thermocouple using a wire brush or emery cloth, ensuring it is free of any debris or corrosion. If the thermocouple is damaged, it will need to be replaced. Proper alignment is also crucial, as the thermocouple tip must be positioned directly in the pilot light flame for it to function correctly.
Thermocouple Specifications:
– Typical thermocouple length: 12-24 inches
– Thermocouple output voltage: 15-30 millivolts (mV) when heated
– Replacement thermocouple should match the original model for proper fit and function
Strong Drafts
Strong winds or drafts can easily extinguish the pilot light, preventing it from staying lit.
Cause: Drafts from windows, doors, or other openings can blow out the pilot light.
Solution: Ensure the gas boiler is installed in a location protected from strong drafts. If the pilot light is being blown out, try relighting it after the draft has passed. Consider installing a draft shield or baffle around the pilot light area to help shield it from external air currents.
Recommended Draft Shielding Specifications:
– Material: Galvanized steel, aluminum, or heat-resistant plastic
– Minimum size: 6 inches tall x 4 inches wide
– Placement: Positioned around the pilot light opening, with a small gap (1-2 inches) to allow airflow
Kinked or Clogged Flex Tube
The flex tube is responsible for supplying gas to the pilot light. If this tube is kinked or clogged, it can restrict the gas flow and prevent the pilot light from staying lit.
Cause: A kink or blockage in the flex tube can disrupt the gas supply to the pilot light.
Solution: Carefully inspect the flex tube for any kinks, bends, or signs of blockage. If the tube is kinked, try to straighten it out. If it is clogged, use compressed air or a pipe cleaner to clear any debris. If the flex tube is damaged, it will need to be replaced.
Flex Tube Specifications:
– Material: Stainless steel or aluminum
– Diameter: Typically 1/4 inch or 3/8 inch
– Length: Varies based on boiler model, usually 12-36 inches
Dirty Pilot Light Opening
Dirt, dust, or debris accumulating in the pilot light opening can interfere with the flame and prevent it from staying lit.
Cause: Obstructions in the pilot light opening can disrupt the gas flow and flame stability.
Solution: Use a wire brush, compressed air, or a small vacuum attachment to thoroughly clean the pilot light opening, removing any visible debris or buildup. Ensure the opening is clear and unobstructed for the pilot light to burn steadily.
Pilot Light Opening Dimensions:
– Diameter: Typically 1/8 inch to 1/4 inch
– Depth: Varies based on boiler model, usually 1/2 inch to 1 inch
Weak Gas Regulator
A malfunctioning gas regulator can prevent the pilot light from receiving sufficient gas pressure to stay lit.
Cause: A faulty or improperly adjusted gas regulator can restrict the gas flow to the pilot light.
Solution: Check the gas regulator and ensure it is functioning correctly. If the regulator is not providing the necessary gas pressure, it will need to be replaced. Consult the boiler manufacturer’s specifications for the recommended gas pressure range.
Gas Regulator Specifications:
– Inlet pressure: Typically 7-14 inches of water column (WC)
– Outlet pressure: Typically 3.5-7 inches of WC
– Replacement regulator should match the original model’s specifications
Incorrect Gas Valve Setting
If the gas valve is not set to the “pilot” position, the pilot light will not stay lit.
Cause: The gas valve must be in the correct “pilot” position to allow gas flow to the pilot light.
Solution: Ensure the gas valve is turned to the “pilot” position and follow the manufacturer’s instructions for properly lighting and adjusting the pilot light. Double-check that the valve is not stuck or malfunctioning.
Gas Valve Positions:
– “Pilot” position: Allows gas flow to the pilot light only
– “On” position: Allows gas flow to the main burners and pilot light
– “Off” position: Shuts off gas flow to the entire system
Bent or Warped Pilot Termination Head
A bent or warped pilot termination head can prevent the pilot light flame from properly enveloping the thermocouple, causing the pilot light to go out.
Cause: Damage or deformation to the pilot termination head can disrupt the flame pattern and prevent proper thermocouple heating.
Solution: Inspect the pilot termination head and check for any signs of bending, warping, or damage. If the head is not in its original shape, it will need to be replaced to ensure the pilot light flame is properly directed onto the thermocouple.
Pilot Termination Head Specifications:
– Material: Brass or stainless steel
– Shape: Typically a small, cylindrical or conical structure
– Replacement head should match the original model’s dimensions and design
Gas Valve Issues
A faulty gas valve can prevent the pilot light from staying lit by restricting the gas flow or failing to open and close properly.
Cause: A malfunctioning gas valve can disrupt the gas supply to the pilot light, causing it to extinguish.
Solution: Carefully inspect the gas valve for any signs of wear, damage, or malfunction. If the valve is not functioning correctly, it will need to be replaced. Ensure the replacement valve matches the original model’s specifications and is properly installed.
Gas Valve Specifications:
– Inlet/Outlet Connections: Typically 1/2 inch or 3/4 inch NPT
– Operating Pressure: Varies based on boiler model, usually 0.5-7 psi
– Replacement valve should have the same connection sizes and pressure ratings
By addressing these common issues, you can effectively troubleshoot and resolve the problem of a gas boiler pilot light that won’t stay lit. Remember to always follow the manufacturer’s instructions and safety guidelines when working on your gas boiler, and consider contacting a professional HVAC technician if you are unsure or uncomfortable with any of the repairs.
References:
– Supertech HVAC. (n.d.). Why Your Pilot Light Keeps Going Out & How To Fix [With Pictures]. Retrieved from https://www.supertechhvac.com/pilot-light-keeps-going-out/
– Wilson Oil and Propane. (2016, October 3). What to Do When Your Gas Furnace Pilot Light Won’t Stay Lit. Retrieved from https://www.wilsonoilandpropane.com/blog/what-to-do-when-your-gas-furnace-pilot-light-wont-stay-lit/
– AC Service Tech. (2018, November 7). TOP 10 Reasons Why the Gas Pilot Light Goes Out & Won’t Stay Lit [YouTube Video]. Retrieved from https://www.youtube.com/watch?v=PiCmfW1rTRY
– Heating Help. (2022, October 26). Replaced thermocouple, but steam boiler pilot won’t stay lit. Retrieved from https://forum.heatinghelp.com/discussion/189662/replaced-thermocouple-but-steam-boiler-pilot-wont-stay-lit
– iHeat. (2022, August 30). Boiler Pilot Light Won’t Stay Lit (How To Fix). Retrieved from https://iheat.co.uk/boiler-help/boiler-pilot-light-going-out