Glow Worm Boiler F28 Fault Code: Causes & Fixes

If you’re dealing with the F28 fault code on your Glow worm boiler, it signals an ignition hiccup that’s left your heating on hold—don’t worry, though; in this detailed guide, I’ll share my firsthand insights on what it means, the typical triggers, and straightforward fixes for each, all tailored to help UK homeowners stay warm and landlords keep tenants happy without the jargon overload.

What Does the Glow Worm Boiler F28 Fault Code Mean?

The Glow Worm boiler F28 fault code means your boiler has failed to ignite properly, locking out as a safety measure to prevent unsafe operation. From my experience troubleshooting these, it’s essentially the boiler’s way of saying “I tried to light up, but something’s off,” often tied to gas flow or component glitches that halt the flame establishment process.

Why Does This Safety Lockout Happen?

This built-in protection kicks in after three unsuccessful ignition attempts, displaying F28 on the panel to alert you—it’s designed to avoid risks like gas buildup, ensuring your central heating system doesn’t run amok.

What Are the Common Causes of the Glow Worm Boiler F28 Fault Code?

The common causes of the Glow Worm boiler F28 fault code usually revolve around disruptions in the gas supply, ignition components, or exhaust pathways, which prevent the burner from lighting reliably.  In some cases, the glow worm boiler error codes may also indicate issues with the thermostat or wiring, which can further complicate the problem. Regular maintenance and inspection can help prevent these faults from occurring, ensuring the system operates efficiently. If the issue persists, consulting a professional technician is advised to diagnose and rectify the underlying cause.

Another potential issue to be aware of are the glow worm boiler F75 error causes, which are often related to low water pressure or problems within the heating system. Addressing these causes promptly is crucial for maintaining optimal performance and avoiding further complications. Regular checks of the pressure levels and ensuring that the system is properly filled can mitigate these issues effectively.

These issues often stem from wear in older units or seasonal woes like cold snaps; let’s dive into the main ones with clear explanations and fixes.

Gas Pressure Issues

Gas pressure issues arise when the supply to your boiler is too low, interrupted by air pockets in the mains, or affected by a frozen regulator in chilly weather, starving the burner of fuel needed for ignition. This is especially common in newly installed Glow Worm boilers where the existing gas line can’t handle the demand, or in UK homes during winter freezes.

How to Fix Gas Pressure Issues

1. Check your gas meter and other appliances—if they’re working, reset the boiler by holding the reset button for 3-5 seconds as per your manual.
2. For suspected air pockets, bleed the gas line by running a gas hob for a few minutes to purge air, but only if you’re comfortable; otherwise, call a pro.
3. If it’s a frozen regulator (often behind the meter), gently thaw with a hairdryer or warm cloth—avoid direct heat sources—and monitor for recurrence.
4. For ongoing low pressure, contact your gas supplier for a mains upgrade or have a Gas Safe engineer assess the pipework.

Frozen Condensate Pipe

A frozen condensate pipe occurs when the wastewater drainage line ices up in sub-zero temperatures, backing up and triggering the ignition fault as the boiler can’t safely expel condensate. I’ve seen this plague exposed external pipes in UK gardens during harsh winters, effectively blocking the system’s operation.

How to Fix a Frozen Condensate Pipe

1. Locate the external condensate pipe (usually a white plastic tube exiting your boiler wall) and identify the frozen section by touch or visible ice.
2. Safely thaw by pouring warm (not boiling) water over it using a jug or watering can, or wrap with a hot water bottle for gradual melting.
3. Once thawed, reset the boiler and test—add lagging insulation like foam sleeves to prevent future freezes.
4. If it doesn’t resolve or refreezes quickly, call a Gas Safe engineer to reroute or insulate the pipe properly.

Faulty Ignition Electrodes or Leads

Faulty ignition electrodes or leads happen due to wear, corrosion from moisture, or vibrations loosening connections, failing to create the spark needed to ignite the gas. In my diagnostics, this is a frequent offender in Glow Worm models over 5-7 years old, especially in humid UK climates.

How to Fix Faulty Ignition Electrodes or Leads

1. Visually inspect accessible parts for damage if safe, but never dismantle—power off the boiler first.
2. Attempt a reset to clear temporary glitches, but if F28 returns, it’s time for professional intervention.
3. Hire a Gas Safe engineer to test resistance with a multimeter and replace faulty electrodes or leads, typically costing £100-£200 including parts.

Blocked Flue or Condensate Drain

A blocked flue or condensate drain develops from debris, bird nests, or internal buildup restricting exhaust flow, causing the boiler to detect unsafe conditions and fail ignition. This ties into poor maintenance in UK properties, where flues in roofs or walls collect grime over time.

How to Fix a Blocked Flue or Condensate Drain

1. Check the external flue terminal for obvious blockages like leaves or nests and clear gently if accessible—use a brush, not hands.
2. For condensate drains, flush with warm water via an access point if available, but avoid forcing if unsure.
3. Engage a Gas Safe professional for a full inspection and cleaning, often involving disassembly to remove sludge or replace sections.

Faulty Gas Valve

A faulty gas valve stems from mechanical failure or solenoid issues, preventing proper gas release to the burner for ignition. From my perspective, this often hits in high-usage landlord setups where valves wear from constant cycling.

How to Fix a Faulty Gas Valve

1. Reset the boiler to rule out electronic hiccups, but don’t tamper with the valve yourself.
2. Call a Gas Safe engineer to diagnose with pressure tests and replace the valve if needed, around £200-£400 for the job.
3. Prevent by scheduling annual services to catch early wear.

Defective PCB (Printed Circuit Board)

A defective PCB arises from electrical surges, moisture damage, or age, sending wrong signals that botch the ignition sequence. I’ve encountered this in Glow Worm boilers exposed to damp or after power fluctuations common in UK grids.

How to Fix a Defective PCB

1. Try a full power cycle—turn off at the isolator for 10 minutes, then restart and reset.
2. If persistent, a Gas Safe expert must test and swap the board, a pricey fix at £300-£600, so check warranty first.

When Should You Get a New Boiler Quote?

If your Glow Worm boiler keeps throwing the F28 fault despite these checks, or it’s an older model racking up repair bills and inefficiency, it’s worth considering a replacement to sidestep ongoing frustrations. Moreover, if you find yourself frequently dealing with issues like the glow worm boiler F1 fault code, this could indicate deeper systemic problems that may not be worth fixing. Investing in a new, more reliable model can provide peace of mind and enhance energy efficiency, ultimately saving you money in the long run. Before making a decision, consider consulting with a qualified technician to discuss the best options available for your heating needs.

Upgrading to a modern, A-rated combi can eliminate these ignition woes, cut energy costs by up to 30%, and ensure compliance with UK eco regs. Request a new boiler quote from Boilers 2 Go tailored to your home or rental. 

FAQs

How does extreme weather in the UK exacerbate Glow Worm F28 faults?

Bitter cold snaps can freeze gas meters or condensate lines, spiking F28 occurrences—insulating outdoor components and scheduling pre-winter checks in vulnerable areas like the North helps mitigate this.

What warranty considerations apply to Glow Worm boilers showing F28?

Most Glow Worm warranties require annual Gas Safe servicing to remain valid for F28-related repairs; check your paperwork or contact the manufacturer to avoid voiding coverage on parts like valves.

Are there smart monitoring tools for detecting F28 precursors in Glow Worm systems?

Apps like Glow Worm’s own connectivity kits can alert to ignition patterns before full F28 lockouts, allowing proactive tweaks in smart-enabled UK homes.

How often should landlords service Glow Worm boilers to prevent F28?

Beyond the legal annual Gas Safe inspection, bi-annual checks in high-tenant turnover properties catch F28 triggers like electrode wear early, ensuring reliability.

Can integrating renewables reduce F28 frequency in Glow Worm setups?

Pairing with solar thermal can ease gas demand, potentially lowering ignition strains that lead to F28, but consult pros for compatible hybrid installs.