Glow-worm Boiler Fault Codes & Repair Guide
Is your Glow-worm boiler showing a flashing fault code? At Thermotec Plumbing & Heating, we believe in helping Wokingham homeowners understand their heating systems. While some issues require a Gas Safe engineer, others can be resolved with a simple DIY fix.
Below is our expert breakdown of the most common Glow-worm errors and exactly how to resolve them.
Glow-worm Boiler Fault Codes: How to Identify and Resolve Common Errors
If your Glow-worm Betacom, Energy, or Ultimate boiler has locked out with a flashing error code, it is signaling a specific internal fault to prevent system damage. Most Glow-worm issues, such as the common F22 low pressure or F28 ignition failure, stem from either simple maintenance needs or component wear. While homeowners can often resolve pressure-related faults by using the filling loop to reach 1.5 bar, codes involving gas supply, the PCB, or the fan require a Gas Safe registered engineer to ensure a safe and permanent repair.
Common Faults Codes Explained:
Fault Code F22 – Low Water Pressure (Dry Fire)
What it means: The system detects insufficient water to operate safely.
Common Causes: Recent radiator bleeding, a leak in the pipework, or a failing pressure sensor.
The Fix: Check your gauge. If it's below 1.0 bar, use the filling loop to repressurise the system to 1.5 bar. Reset the boiler once the pressure is restored.
Fault Code F1 / F28 / F29 – Ignition & Flame Failure
What it means: The boiler has failed to light or the flame has been interrupted.
The Fix: Ensure your gas supply is active (check other gas appliances). In winter, inspect the external condensate pipe for ice. Thaw it with warm water and press the reset button.
Expert Note: If the boiler locks out repeatedly, the spark generator or flame sensing probe is likely faulty.
Fault Code F75 – Pump or Pressure Sensor Fault
What it means: The boiler doesn't detect a "pressure spike" when the pump starts.
Why it happens: This is a common issue where the pressure sensor becomes blocked with system "sludge" or the pump has seized.
The Fix: This requires a Gas Safe registered engineer. We will test the sensor and pump, and we often recommend a Powerflush if debris is the root cause.
Professional Glow-worm Boiler Repairs in Wokingham
When a simple reset won't clear the fault, you need a Glow-worm specialist who knows exactly where to look. Persistent error codes or a boiler that refuses to ignite usually indicate an internal component failure—often involving the ignition electrodes, a seized pump, or a blocked pressure sensor. At Thermotec Plumbing & Heating, we don’t just reset the display; we diagnose the root cause to ensure your heating stays on for good.
Why Choose Stuart for Your Glow-worm Repair?
Manufacturer Trained: 20+ years of experience with Betacom, Energy, and Ultimate models.
First-Time Fix Focus: We carry common Glow-worm spares to get you back up and running today.
Gas Safe Registered: Certified expertise for safe, legal, and thorough repairs.
Fixed-Price Diagnostics: No hidden hourly "surprises"—just honest, local service.
Boiler Still Not Firing Up?
Call Stuart on 07850 116944 for immediate expert assistance in Wokingham, Crowthorne & Berkshire.
Glow-worm Boilers: Frequently Asked Questions
-
The F28 and F29 codes are the most common errors for Glow-worm Energy and Ultimate models. They indicate an ignition failure—essentially, the boiler tried to light but failed (F28) or lost the flame during operation (F29). In the Wokingham area, this is often caused by a blocked condensate pipe during winter, a faulty gas valve, or a dirty spark electrode. Always check that your gas meter hasn't been accidentally shut off before calling an engineer.
-
If your Glow-worm display is flashing F22, your system pressure has dropped below the safety limit. You can usually fix this yourself by locating the filling loop (a silver braided hose) underneath the boiler. Open the blue or black plastic valves slowly until the digital display or manual gauge reads 1.5 bar. Once the pressure is restored, the code should disappear, and the boiler will fire up. If this happens frequently, you may have a slow leak or a failing expansion vessel.
-
Loud noises in a Glow-worm boiler are usually a sign of "kettling," often linked to an F75 or F24 fault. This happens when lime-scale or "sludge" builds up in the primary heat exchanger, restricting water flow. This makes the water boil too quickly (like a kettle). As a Wokingham heating specialist, I recommend a professional Powerflush or a chemical system cleanse to clear the debris and restore quiet, efficient operation.
-
Yes. To reset a Glow-worm boiler, look for the button with a flame symbol with a line through it or a button marked "Reset." Press and hold it for three seconds. If the boiler lockouts again immediately, do not keep resetting it. Repeatedly forcing an ignition can damage the PCB or the burner. If a reset doesn't clear the code, it’s a sign that a safety component has failed.
-
To keep your Glow-worm manufacturer warranty valid (which can be up to 10 years on certain models), you must have a Gas Safe registered engineer perform an annual service. During a Thermotec service, we don't just check for safety; we clean the burner, check the expansion vessel pressure, and test the flue gases. This prevents common faults like the F27 or F28 from happening in the first place.
-
The F75 code is very common and usually indicates a faulty Pressure Sensor. The boiler needs to see a "pulse" from the pump to know it's safe to fire. If the sensor is blocked with sludge or has failed, it can't see that pulse. While it’s not a "major" engine failure, it does require a part replacement. I carry genuine Glow-worm sensors on my van to get Wokingham homes back up and running in a single visit.