Boiler Fault Guide
Glow-worm Boiler Fault Codes: F28, F9, F22 and What to Check Safely
Glow-worm boiler fault codes identify a condition detected by a particular model; match the complete display to that model’s instructions before checking pressure, attempting a reset or arranging repair. This guide helps householders in London record the fault and choose a safe next step.
Smell gas: leave, call the National Gas Emergency Service on 0800 111 999. For suspected carbon monoxide symptoms, get into fresh air and contact NHS 111, or 999 if serious. Never open the boiler casing or work on gas.
Call with your postcode, the boiler make and any fault code showing.
- Gas Safe registered: 648977
- Phone line open 24/7
- Same-day appointments available
Before Any Checks: Gas Smells, CO Alarms and Unsafe Boilers
Gas smells, a sounding CO alarm or suspected exposure take priority over troubleshooting.
- Gas smell: avoid flames and electrical switches. Open doors and windows and turn off gas at the meter only if safe. Get outside and call 0800 111 999 from a safe place. Read what to do if you smell gas.
- CO alarm or exposure: get into fresh air. Seek medical help for suspected symptoms through NHS 111, or 999 for serious symptoms. Then contact the gas emergency service without delaying medical help. CO has no smell; treat an alarm as real. Read carbon monoxide symptoms and alarm response.
Leave any boiler labelled unsafe switched off.
Identify Your Glow-worm Model and Copy the Complete Display
You need the range, model and complete display before choosing an explanation. Use paperwork or safely accessible external identification, never casing appearance alone.
Record:
- Full model name and suffix.
- Complete code, including punctuation.
- Pressure reading and whether the system is cold.
- Whether heating, hot water or both have stopped.
- A photograph of the display without opening anything.
Operating symbols are not necessarily faults: see what boiler fault codes and display messages mean. If you cannot identify the model, give your observations to an engineer.
Glow-worm Fault-Code Lookup by Model
Use only an entry matching your model and complete code; this is not an exhaustive list.
Energy7 F.28
unsuccessful ignition during start-up. Supply, ignition or condensate problems are possibilities. Check only permitted user information; leave internal investigation to an engineer.
Flexicom cx F9
the manufacturer lists pressure-sensor, flow-filter and pump faults. Record pressure; do not assume adding water will help.
Energy7 F.22
water-deficiency safety shutdown. Check the gauge and model instructions before considering a top-up.
Energy7 F.75
pressure-sensor fault. Record the reading and arrange assessment; this does not establish pump failure.
Energy7 F.83
inadequate temperature change at burner start. Water deficiency or sensor-position issues are possibilities. Internal checks require an engineer.
The Energy7 entries below refer to Glow-worm installation instructions 0020300875_01, Appendix E. The Flexicom entry refers to Glow-worm’s Flexicom cx fault-code support table.
Verify: check against the manufacturer's manual
For an unmatched code or range, check the exact manual rather than choosing the nearest entry.
F28 on a Glow-worm Boiler: What the Ignition Fault Tells You
On the Energy7 models covered by the cited manual, F.28 means ignition was unsuccessful during start-up. It does not identify a failed component.
F1, F4 and F29: Why Similar Symptoms Need Different Code Entries
These codes need separate model checks even when the boiler will not fire. Glow-worm’s Flexicom cx table lists ignition-related F1 and F4 entries; Energy7 F.29 concerns flame loss. A bare F1 is not a universal ignition code. Confirm the legacy model’s manual before selecting an action.
After excluding gas and CO concerns, check prepayment credit where relevant. Observe condensate pipework only where safely accessible outside. Do not light another appliance as a test, clean internal parts or adjust gas components. Any reset must follow the exact operating instructions; stop after one permitted attempt if the fault persists or returns.
Glow-worm Boiler Pressure: Read the Gauge Before Adding Water
Check pressure against your model’s instructions before adding water. The gauge shows heating-system water pressure, not gas or tap-water pressure. Record whether the system is cold or running: an operating range is not automatically the cold filling target. See understanding boiler pressure and safe topping-up.
F9 on a Glow-worm Boiler: Do Not Assume It Only Needs Topping Up
Flexicom cx F9 includes pressure-sensor, flow-filter and pump faults in the manufacturer’s support table. A low reading warrants checking the user instructions; a normal reading with a continuing fault warrants assessment. Neither reading confirms a failed part. Do not access the pump or remove filters.
F22 on a Glow-worm Boiler: Check the Model Before Repressurising
Energy7 F.22 indicates a water-deficiency shutdown. Only top up if the reading warrants it and the exact user instructions permit it. Identify the correct filling controls, follow the specified target and close them afterwards. Stop if uncertain, pressure falls again, or the code persists despite a normal reading.
F75 on a Glow-worm Boiler: What the Model Manual Says
The cited Energy7 manual describes F.75 as a pressure-sensor fault. That is an indication requiring diagnosis, not proof that a new pump is needed. Record pressure and affected functions for an engineer. Do not bypass the fault, manipulate the pump or add water automatically.
Glow-worm Boiler Pressure Too High or Falling Again
Stop adding water if pressure exceeds your model’s limits or falls again after an instructed top-up. Record existing cold and running readings and visible leakage without touching hot pipework. An engineer may investigate the filling arrangement, expansion vessel or relief valve. Do not operate safety valves or block discharge pipes.
F83 on a Glow-worm Boiler: Match the Manual, Then Stop Guessing
Energy7 F.83 concerns insufficient temperature change when the burner starts, according to Appendix E of the cited manual. Water deficiency and temperature-sensor positioning are possible causes, not confirmed diagnoses. Record the symptoms and leave internal investigation to an engineer; do not reposition sensors or repeatedly reset.
F11, F13 and F14: The Same Number Can Mean Different Things
F11, F13 and F14 require range-specific definitions. Glow-worm’s cxi support table associates F14 with excessive heating-flow temperature; its Flexicom cx table associates F14 with gas-valve control. F11 and F13 also need the exact manual before interpretation. Internal electrical, sensor and gas-control checks belong to an engineer.
Other Codes: F3, F5, F20, F23, F25, F32, F72 and F73
These codes require model confirmation before assigning a meaning or action. If your exact range and display are not covered here, consult its operating instructions or arrange assessment. Do not transfer definitions between ranges, bypass a lockout, or attempt fan, wiring, flue, pump or safety-device repairs.
Glow-worm Boiler Has No Hot Water: What to Record and Check
A boiler with no hot water needs its display, settings and affected functions checked before the cause can be established.
Hot water only affected
record whether heating works and confirm whether the boiler is a combi.
Heating only affected
check accessible timer, thermostat and operating-mode settings against their instructions.
Both affected
record the code and accessible power indication.
No code
record the same observations; an empty fault display does not identify the cause.
See checks when heating or hot water stops working. Do not open the casing or access wiring.
When to Stop Checking and Call a Gas Safe Engineer
Call a suitably qualified Gas Safe engineer when the fault persists or returns after one permitted reset. Stop when:
- You cannot identify the model or controls.
- Pressure repeatedly falls.
- Pressure is outside the model’s limits.
- You see leakage.
- A check requires internal access.
Arrange boiler repair and assessment in London so the cause can be established before selecting parts. Share the model, code, pressure, affected functions and actions attempted. Gas or CO concerns require emergency action first.
Boiler repair, servicing and gas work
Arrange a Glow-worm Boiler Repair in London
For a persistent Glow-worm fault in London, call All Service 4 U to discuss an appointment with our Gas Safe registered engineers, business registration 648977. Call us 24 hours a day, 7 days a week.
Have your model, complete code, pressure reading and affected functions ready.
Discuss a Boiler Repair: 020 3740 6785
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Frequently Asked Questions
How Do I Reset My Glow-worm Energy 30c Boiler?
Use the instructions for your exact Energy 30c version, and stop if the fault persists or returns after one permitted attempt. Energy7 instructions are not interchangeable merely because both names include 30c. Exclude gas and CO concerns first. Clearing the display does not prove repair.
How Do I Adjust the Water Temperature on My Glow-worm Boiler?
Use only the temperature controls described in your model’s user instructions. Domestic hot-water temperature and heating-flow temperature are different settings, and an external controller may affect adjustment. Check the actual boiler and controller combination before changing anything. Adjusting a comfort setting does not repair a fault code; leave installer settings alone.
Does a Flashing Symbol or Plus Sign Mean My Boiler Has a Fault?
A flashing symbol or plus sign needs matching to your model’s display key before it can be interpreted. Record the symbol, accompanying numbers and whether it flashes continuously or intermittently. It may concern an operating mode or adjustable value rather than a fault. A plus sign is not a universal reset instruction.
Could Freezing Weather Explain a New Glow-worm Fault?
A frozen external condensate pipe is one possibility, but the code alone cannot confirm it. Observe only safely accessible external pipework. If appliance guidance permits thawing, use warm, never boiling, water. Avoid flames, unsafe ladder work and internal trap access. Read about safely checking a frozen condensate pipe before proceeding.
Can I Restart a Boiler an Engineer Has Labelled Unsafe?
Do not restart an unsafe or disconnected boiler until a suitably qualified engineer has made it safe. A disappearing display code does not overturn an engineer’s safety finding. Follow the written warning and ask the engineer to clarify anything unclear. Gas smells, CO alarms or suspected exposure require the emergency actions above.
How Can I Check the Engineer Is Qualified to Work on My Boiler?
Check the engineer’s Gas Safe ID card: match the photograph to the person, check validity and confirm relevant boiler-work categories. Verify their current registration through Gas Safe Register. A business registration number does not replace checking the attending individual. Read our guide to.
Still have a question or need urgent assistance? Call 020 3740 6785, tell us what has happened and we will tell you what happens next.