Vaillant F28 Fault Code

The F28 fault code on Vaillant boilers indicates an ignition failure. The boiler has attempted to ignite but failed, typically after 3 unsuccessful attempts.

What Does F28 Mean?

This error appears when:

• The boiler cannot detect a flame after sparking
• There are repeated ignition failures
• The flame doesn't establish within the allowed time

Common Causes

1. No Gas Supply

Most Common Cause

• Gas meter turned off
• Gas supply interrupted
• Prepayment meter needs topping up
• Gas valve closed

2. Low Gas Pressure

• Supply pressure too low for ignition
• Regulator issues
• Network problems

3. Ignition Electrode Problems

• Electrodes worn or damaged
• Incorrect electrode gap (should be 3-4mm)
• Carbon buildup on electrodes

4. Faulty Gas Valve

• Gas valve stuck or failing
• Electrical connection issues

5. Flue/Combustion Issues

• Blocked flue
• Condensate trap blockage
• Poor ventilation

Step-by-Step Fixes

Step 1: Check Gas Supply

1. Try another gas appliance (cooker/hob)
2. Check gas meter is on
3. Verify prepayment meter has credit
4. Ensure gas isolation valve is open

Step 2: Reset the Boiler

1. Press the reset button (flame icon)
2. Wait for the boiler to attempt ignition
3. If successful, problem may have been temporary

Step 3: Check for Blockages

1. Inspect external flue terminal
2. Remove any obstructions
3. Check condensate pipe isn't frozen (winter)

When to Call an Engineer

You must call a Gas Safe registered engineer if:

• Gas supply is confirmed but boiler won't ignite
• You smell gas (call 0800 111 999 immediately)
• The reset doesn't work
• Fault returns repeatedly
• Boiler makes unusual noises

What the Engineer Will Check

1. Gas pressure at the meter and boiler
2. Electrode condition and gap
3. Gas valve operation
4. Ignition PCB functionality
5. Flue integrity
6. Combustion chamber condition

Repair Costs

Issue	Typical Cost
Simple reset/gas valve	£80-£120
Electrode replacement	£120-£200
Gas valve replacement	£200-£350
PCB replacement	£250-£450

Should You Repair or Replace?

Repair Makes Sense If:

• Boiler is under 5 years old
• Single isolated fault
• Repair cost under £250

Consider Replacement If:

• Boiler is 8+ years old
• Multiple recent faults
• Repair exceeds £400
• Efficiency rating below 85%

Potential savings with a new A-rated boiler: £400-£600/year

Prevent F28 Errors

• Annual boiler service
• Check gas meter regularly
• Keep flue clear
• Maintain proper ventilation
• Service condensate trap

Get Help Fast

Immediate Repair: Call us now for same-day engineer visit

New Boiler Quote: Replace your old boiler with a modern, reliable model

Modern Vaillant boilers come with 10-year warranties and smart controls as standard.