James Elston

Published April 9, 2024

The Glow-worm F28 boiler fault indicates that your boiler has failed to ignite, which can lead to a loss of heating and hot water. This can be due to many factors, including a frozen condensate pipe, gas supply issues, or a fault with the ignition lead. 

Not addressing the issue promptly could result in further damage, your boiler not working, and potentially dangerous situations.

This article will look at what an F28 error code is, what you can do to fix it, and why addressing it immediately is essential.

What Is A Glow-worm F28 Fault Code?

A Glow-worm boiler F28 error code alerts you to an ignition fault. It is an indication that the boiler attempted to ignite but was unsuccessful. This could be related to the gas supply, flue, gas valve, electrode spark generator or printed circuit board (PCB).

It’s a safety feature designed to ensure that your boiler doesn’t operate when there are potential issues that could compromise your safety or the efficiency of your central heating system.

Ignoring the F28 code can lead to a host of problems. Firstly, your home may not be as warm and cosy as you desire. Additionally, there are safety concerns involved.

For example, if your boiler fails to ignite due to a gas leak (which causes an insufficient supply of gas), it poses a severe fire hazard. If your boiler has a faulty fan, it may not extract the harmful combustion gasses properly, causing the risk of carbon monoxide poisoning. 

When the F28 code appears, you must act immediately to resolve the problem. Ignoring this warning might mean bypassing these safety measures, which you don’t want to compromise.

Common causes of an F28 fault code

Let’s look at some common issues that can cause your Glow-worm boiler to display the F28 error code.

Insufficient gas supply

When your boiler doesn’t receive an adequate supply of gas, it won’t be able to ignite and function properly. Similar to a Vaillant boiler fault code, the F28 error code on your Glow-worm boiler indicates that something is obstructing the gas flow.

The signs of this problem may include an inconsistent flame, no flame, or fluctuating or low-pressure readings on your boiler’s gauge (the ideal pressure range is between 1 and 1.5 bars).

Frozen condensate pipe

A condensate pipe carries the boiler’s wastewater to an external drain. In freezing temperatures, this condensate pipe can freeze, causing a blockage.

If you hear gurgling or bubbling sounds coming from your boiler, this could indicate a frozen condensate pipe.

Debris in the burner

The burner combusts gas to generate heat for your boiler. An accumulation of debris can disrupt the combustion process, triggering the F28 error code.

Keep an eye on irregular flame patterns or unusual noises during the ignition process, as these may be a sign that there’s an issue.

Faulty spark generator

The spark generator and ignition leads create the spark that ignites the gas in the burner. However, a damaged or malfunctioning spark generator can result in difficulties initiating the ignition process.

You can identify this issue by checking if there is no clicking sound during ignition and if the flame appears inconsistent or absent.

Step-By-Step Troubleshooting Guide

Before contacting a Gas Safe engineer, use the following DIY troubleshooting steps to pinpoint and potentially resolve a frozen condensate pipe problem.

While troubleshooting boilers, consider the following safety precautions:

  • Before you begin troubleshooting, it’s crucial to prioritise your safety. Make sure to turn off the boiler and other gas appliances connected to it to avoid burns and other injuries.
  • Ensure that the area where you’ll be working has proper ventilation before you start.
  • Dealing with electrical components is dangerous and illegal, especially if you’re not a certified professional. It’s always best to leave this task to the experts who are adequately trained and certified.

If you’re experiencing a more complex issue like a fault spark generator, or don’t know what to do, it’s best to contact a registered Gas Safe engineer.

Step 1: Identify the fault code

Look at the display panel to identify the F28 error code on your boiler. You can also check for other signs, such as the boiler failing to ignite, regular shutdowns, audible clicking noises, or the smell of gas.

  • To resolve the issue, start by resetting your boiler.
  • Hold the button for approximately 10 seconds to clear the fault code and restore normal operation.
  • If resetting doesn’t do the trick, it’s worth checking if there are any blockages or debris in the gas supply line or flue. Should you find any obstructions, gently use a brush to clear them.

Step 2: Check the gas supply

Before checking the gas supply, ensure all gas appliances in your home are turned off.

  • Check the pressure gauge on your boiler. It should be within the recommended range set by the manufacturer. The recommended pressure for your Glow-worm boiler is between 1 and 1.5 bar.
  • If you notice the gas flow pressure levels are too low, avoid trying to fix the issue on your own. Instead, contact a Gas Safe registered engineer. This could be a faulty gas valve or a mechanical fault that requires a skilled professional.

Step 3: Thaw the condensate pipe

To thaw a frozen condensate pipe, try the following:

  • Locate the condensate pipe: The condensate pipe is located near the bottom of the boiler. It is usually a white pipe that runs to the outside of a building. 
  • Pour warm water: Take a watering can or any suitable container and pour warm water gently alongside the pipe. Avoid using boiling water as it may cause damage to the pipe
  • Use a hot water bottle: Place a hot water bottle or microwavable heat pad around the pipe.
  • Apply a warm cloth: Soak a cloth in hot water and cover the pipe with it.

Step 4: Call a professional

If you’ve checked the gas supply and boiler pressure (following the steps listed above) but the F28 error code persists, you should contact a registered gas engineer. 

A Gas Safe engineer has the expertise and advanced testing equipment to diagnose and repair problems with components, such as:

  • Gas valve fault
  • Ignition electrode
  • Spark generator
  • Faulty PCB
  • Wiring

Tampering with these components is illegal and dangerous, and can void your warranty.

Preventive Measures For The F28 Fault Code

To maintain the performance of your Glow-worm boiler, it’s crucial to go beyond responding to the error codes. Eco Happy believes that adopting a proactive approach will not only safeguard your heating system but also extend its lifespan.

Here are a couple of maintenance tips to keep your boiler in good working order.  

Annual boiler servicing

So, how often should you service your boiler? You should have your boiler serviced and maintained annually. This practice helps address any issues before they become major problems. By maintaining your boiler, you can ensure that it operates efficiently, resulting in energy bill savings.

It allows for the detection and resolution of any safety risks. Moreover, routine maintenance extends the lifespan of your boiler, protecting your long-term investment.

Monitoring gas supply and combustion

Checking the gas supply regularly and monitoring the combustion quality is essential to avoid encountering error codes like the F28. A reliable gas supply ensures that heat is produced by your boiler, while monitoring helps prevent gas-related issues that may trigger fault codes.

Protection from external factors

External factors, like freezing temperatures, debris, or blockages, can impact your boiler’s efficiency. You must take the following measures to protect your central heating system from these influences:

  • Ensure you have proper insulation for vulnerable components, like the condensate pipe.
  • Regularly check the vents, air intakes and exhaust outlets for debris or blockages and remove them as necessary.
  • If your boiler is outdoors, consider installing covers to shield it from harsh weather conditions.


Is it safe to reset a boiler?

After encountering an error code like F28, it is typically safe to reset a boiler. Before resetting, it is crucial to address the root cause of the fault to avoid safety hazards. If the issue persists, or you are unsure of how to proceed, it’s best to seek professional assistance from a registered Gas Safe engineer.

What are the signs of boiler failure?

Your boiler is likely faulty if you notice irregular heating patterns, strange noises, leaks, or the smell of gas. Most modern boilers have LCDs that will show you an error code. However, it would be best to ask a Gas Safe engineer to diagnose the issue. Some issues, like faulty gas valves, ignition faults, or replacement parts, are covered by your warranty.

What are the symptoms of an airlock in a boiler?

Audible boiler noises, like gurgling, tapping, or bubbling, are symptoms of an airlock. Bleeding the radiators and managing the trapped air within the system can often resolve the issue.


Dealing with an F28 error code on your Glow-worm boiler is not just about technicalities. It’s also crucial for ensuring your heating system’s effectiveness, safety, and longevity.

Identifying and addressing the underlying issue causing the F28 error code is vital, as ignoring it could pose safety risks and potentially cause long-term damage to your boiler.

Don’t hesitate to contact Eco Happy today for additional assistance and tailored solutions for all your boiler needs.

James Elston

Boiler Expert

James Elston is the top boiler replacement and heating expert at Eco Happy. He has over 20 years of experience in the industry, focusing on Gas Safe boiler installations and offering home-heating and energy-saving solutions to homeowners across the UK. From sourcing the most energy-efficient combi boiler to providing specialist heating advice, James ensures that Eco Happy maintains the highest standards and best customer service.

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