Glow Worm Energy 25c fault F.28: The boiler's completely dead, no heating or hot water at all

1. 1. Verify gas supply to the property.

   Why: A lack of gas is the most common and simplest reason for an ignition failure.

   How: Check if other gas appliances in the property (e.g., gas hob, gas fire) are working. Ensure the gas meter's emergency control valve (ECV) is open and, if it's a prepayment meter, that there is sufficient credit.

2. 2. Inspect the condensate pipe for blockages.

   Why: A blocked or frozen condensate pipe can prevent the boiler from operating and lead to an F.28 fault, especially in colder weather.

   How: Locate the white plastic condensate pipe, typically exiting the boiler and running outside. Look for any visible obstructions or signs of freezing. If frozen, gently thaw with warm (not boiling) water.

3. 3. Check the ignition electrode and lead for damage or wear.

   Why: Faulty or worn ignition electrodes and leads can prevent a strong spark, leading to ignition failure.

   How: Visually inspect the ignition electrode for cracks, corrosion, or carbon build-up. Check the ignition lead for any signs of damage or loose connections. This requires opening the boiler casing.

4. 4. Test the gas valve operation.

   Why: A faulty or incorrectly adjusted gas valve will prevent the correct amount of gas from reaching the burner, causing ignition failure.

   How: Using appropriate test equipment, verify that the gas valve is opening and receiving the correct voltage during the ignition sequence. This requires electrical testing and gas pressure checks.

5. 5. Examine the flame sensing electrode/ionisation probe.

   Why: If the flame sensor is dirty or faulty, it may not detect a flame even if ignition occurs, causing the boiler to shut down as a safety measure.

   How: Inspect the flame sensing electrode for cleanliness and integrity. Clean any carbon deposits if present. Check its connection and resistance.

6. 6. Inspect the burner for debris or blockages.

   Why: Debris, such as carbon build-up, in the burner can obstruct the gas flow and prevent proper ignition.

   How: Carefully remove the burner and visually inspect the jets for any blockages. Clean as necessary using appropriate tools.

7. 7. Assess the Printed Circuit Board (PCB).

   Why: The PCB controls the ignition sequence; a fault here can lead to incorrect signals and prevent the boiler from lighting.

   How: Visually inspect the PCB for any signs of burning, damage, or loose connections. If all other components test correctly, the PCB may be faulty. This is typically a last resort diagnosis.

Commonly failed parts

• Ignition Electrode and Lead Assembly
• Gas Valve
• Flame Sensing Electrode (Ionisation Probe)
• Printed Circuit Board (PCB)

More Glow Worm fault codes

• Energy 25c — fault F.32 →

Browse all Glow Worm fault diagnostics →

Sources

The AI cross-checked the following manufacturer and trade sources while producing this checklist.

• thamesboilers.co.uk
• housewarm.co.uk
• skillstg.co.uk
• thermo-tec.co.uk
• heatable.co.uk
• youtube.com
• justanswer.co.uk
• serviceteam.co.uk