Glow-worm
Betacom 4 28kW
Combi Boiler
28kW
2014-2020
ErP A
101 fault codes
<p>The Betacom 4 28kW is a combi boiler from Glow-worm, available at 28kW output. Produced 2014-2020.</p>
Betacom 4 28kW Fault Codes 101
Code
Description
Severity
Type
F.00
Flow Temperature Sensor Fault (Energy Range)
On Glow-worm Energy range boilers, F.00 indicates a fault with the flow temperature sensor. Identical to…
Medium
Engineer
View Guide
F.10
Flow Temperature Sensor Short Circuit (Energy)
On Glow-worm Energy boilers, F.10 indicates the flow temperature sensor has short-circuited.
Medium
Engineer
View Guide
F.11
Return Temperature Sensor Short Circuit (Energy)
On Glow-worm Energy boilers, F.11 indicates the return temperature sensor has short-circuited.
Medium
Engineer
View Guide
F.20
Safety Overheat (Energy Range)
On Glow-worm Energy boilers, F.20 indicates the safety overheat temperature has been reached. The boiler has…
High
Engineer
View Guide
F.25
Flue Gas Temperature Too High (Energy Range)
On Glow-worm Energy boilers, F.25 indicates the flue gas temperature has exceeded safe limits.
High
Engineer
View Guide
F.27
Flame Detection Fault (Energy Range)
On Glow-worm Energy boilers, F.27 indicates a fault in the flame detection circuit. Shared with older…
High
Engineer
View Guide
F.33
Air Pressure Switch Fault (Energy Range)
On Glow-worm Energy boilers, F.33 indicates an air pressure switch fault — the switch is not…
High
Engineer
View Guide
F.82
Gas Valve Switch-Off Control Fault (Energy Range)
On Glow-worm Energy boilers, F.82 indicates a fault in the gas valve switch-off control circuit.
High
Engineer
View Guide
F.83
EEPROM Fault (Energy Range)
On Glow-worm Energy boilers, F.83 indicates an EEPROM (memory) fault — the PCB electronics are defective.
High
Engineer
View Guide
F.87
Electrode Fault (Energy Range)
On Glow-worm Energy boilers, F.87 indicates an ignition or sensing electrode fault.
Medium
Engineer
View Guide
F.88
Unstable Flame / Gas Valve Fault (Energy Range)
On Glow-worm Energy boilers, F.88 indicates an unstable flame signal — possible underfloor heating contact issue…
High
Engineer
View Guide
F.89
Pump Fault (Energy Range)
On Glow-worm Energy boilers, F.89 indicates a pump fault.
High
Engineer
View Guide
F00
Flow Temperature Sensor Fault (Betacom/Ultracom)
On Glow-worm Betacom and Ultracom models, F00 (or F10, F71) indicates a flow heating temperature sensor…
Medium
Engineer
View Guide
F01
Return Temperature Sensor Fault (Betacom/Ultracom)
On Glow-worm Betacom and Ultracom models, F01 (or F11) indicates a return heating temperature sensor fault.
Medium
Engineer
View Guide
F1
Ignition Failure / Lockout
The boiler has failed to ignite after five attempts and entered lockout. In winter, the most…
Medium
DIY
View Guide
F10
CH Return Thermistor Fault (Older Ranges)
On older Glow-worm ranges, F10 indicates a central heating return thermistor fault.
Medium
Engineer
View Guide
F11
Flow/Return Temperature Sensor Fault
A temperature sensor (NTC thermistor) on either the flow or return pipework has failed or has…
Medium
Engineer
View Guide
F12
PCB Fault / Communication Error
The PCB has detected an internal fault or a communication error with a connected controller.
High
Engineer
View Guide
F13
DHW Temperature Sensor Fault
The domestic hot water temperature sensor has failed or has a wiring issue. On combi boiler…
Medium
Engineer
View Guide
F14
Gas Valve Control Defective (Older Ranges)
On Glow-worm Flexicom and Ultracom models, F14 indicates the gas valve control is defective.
High
Engineer
View Guide
F15
eBUS Voltage Fault (Older Ranges)
On Glow-worm Flexicom and Ultracom models, F15 indicates an eBUS voltage failure.
Medium
Engineer
View Guide
F16
Fan / Wiring Fault
The fan has a fault in its motor or wiring. Different from F32 which is a…
High
Engineer
View Guide
F17
Gas Valve Closing Fault
The gas valve is not closing properly after the burner shuts down.
High
Engineer
View Guide
F19
Flow/Return Differential Too High
The temperature gap between flow and return is too large, indicating poor circulation.
Medium
Engineer
View Guide
F2
Flame Supervision Fault
The flame supervision device has detected an issue with the flame signal.
High
Engineer
View Guide
F20
Safety Overheat Lockout
The safety thermostat has triggered due to overheating. Identical to Vaillant F.20 as Glow-worm uses the…
High
Engineer
View Guide
F21
Flow Rate Sensor Fault
The water flow rate sensor is giving incorrect readings.
Medium
Engineer
View Guide
F22
Low Water Pressure
The system water pressure has dropped below the minimum required level. This is the modern equivalent…
Low
DIY
View Guide
F23
Temperature Spread Too High
The difference between flow and return temperatures is too great, indicating poor circulation.
Medium
Engineer
View Guide
F24
Rapid Temperature Rise
The flow temperature is rising faster than 10°C per second, indicating a circulation problem.
High
Engineer
View Guide
F25
Circulation Fault (All Ranges)
On all Glow-worm boiler ranges, F25 (or F23) indicates a circulation fault — insufficient water flow…
Medium
Engineer
View Guide
F26
Gas Valve Stepper Motor Fault
The gas valve stepper motor is not responding correctly.
High
Engineer
View Guide
F27
Ionisation Fault Despite Gas Valve Off
A flame signal is detected even though the gas valve should be closed.
High
Engineer
View Guide
F28
Ignition Failure (Modern Models)
On newer Glow-worm Energy and Ultimate models, F28 indicates the boiler has failed to detect a…
Medium
DIY
View Guide
F29
Flame Loss During Operation
The boiler ignited but then lost the flame during operation.
Medium
DIY
View Guide
F3
Flue Gas Sensor Fault
The flue gas temperature sensor is reading outside normal range.
High
Engineer
View Guide
F30
Outdoor Sensor Fault
The outdoor temperature sensor is disconnected or faulty.
Low
Engineer
View Guide
F31
Outdoor Sensor Short Circuit
The outdoor NTC sensor wiring has a short circuit.
Low
Engineer
View Guide
F32
Fan Error
The boiler fan is not running at the required speed. Shared with Vaillant as part of…
High
Engineer
View Guide
F33
Flue Gas Recirculation
Flue gases are being drawn back into the air intake, affecting combustion.
High
Engineer
View Guide
F34
Mains Voltage Fault
The mains supply voltage is outside the acceptable range.
Medium
Engineer
View Guide
F35
Mains Frequency Fault
The mains supply frequency is outside the acceptable 50Hz range.
Medium
Engineer
View Guide
F36
eBUS Communication Fault
The communication bus between boiler components has failed.
High
Engineer
View Guide
F39
Outdoor Temp Sensor — Freeze Warning
The outdoor sensor has detected a temperature near freezing. Frost protection may be active.
Medium
DIY
View Guide
F4
Gas Supply / Ignition Lockout
The boiler has failed to ignite after five attempts — typically indicating a gas supply issue…
Medium
DIY
View Guide
F41
DHW Sensor Open Circuit
The domestic hot water NTC sensor has an open circuit.
Medium
Engineer
View Guide
F43
Generic Internal Error (Flexicom/Ultracom)
On Glow-worm Flexicom and Ultracom models, F43 indicates a generic internal fault code.
High
Engineer
View Guide
F44
Diverter Valve Fault
The diverter valve is stuck or not switching correctly.
Medium
Engineer
View Guide
F45
DHW Sensor Short Circuit
The DHW NTC sensor wiring has a short circuit.
Medium
Engineer
View Guide
F46
Low Gas Pressure Detected
The boiler is detecting that the gas supply pressure is too low.
High
Engineer
View Guide
F47
Mixed Gas Pressure Fault
Both low gas pressure and flame supervision faults are occurring.
High
Engineer
View Guide
F48
Phase/Neutral Reversed
The mains electricity supply has reversed live and neutral connections.
High
Engineer
View Guide
F49
eBUS Communication Fault
Communication failure between the boiler and a connected Vaillant Group controller (sensoCOMFORT, sensoHOME, MiGo etc.) over…
Medium
Engineer
View Guide
F5
Overheat Fault
The boiler has detected an overtemperature condition and shut down for safety. On older Glow-worm Betacom…
High
Engineer
View Guide
F50
DHW Thermistor Open Circuit
The hot water thermistor circuit is broken.
Medium
Engineer
View Guide
F51
Flow Thermistor Drift
The flow sensor readings are drifting outside expected values.
Medium
Engineer
View Guide
F52
Cylinder Sensor Fault
The hot water cylinder NTC sensor has a fault (system boilers).
Medium
Engineer
View Guide
F54
Gas Pressure Too Low
The gas supply pressure to the boiler is below the minimum required.
High
Engineer
View Guide
F55
CO Sensor Fault
The carbon monoxide safety sensor is not reading correctly.
High
Engineer
View Guide
F59
Comfort Mode Fault
A fault has occurred in the comfort/pre-heat operating mode.
Medium
Engineer
View Guide
F6
CH Flow Thermistor Fault (Older Ranges)
On older Glow-worm ranges, F6 indicates a central heating flow thermistor fault.
Medium
Engineer
View Guide
F60
Gas Valve Driver Fault
The PCB is unable to drive the gas valve correctly.
High
Engineer
View Guide
F61
Gas Valve Regulation Error
The gas valve has an electronic fault. Shared fault code across the Vaillant Group.
High
Engineer
View Guide
F62
Gas Valve Timing Fault
The gas valve is not opening/closing with the correct timing.
High
Engineer
View Guide
F63
EEPROM Fault
Memory fault on the main PCB. The boiler cannot read its stored configuration data.
High
Engineer
View Guide
F64
NTC Sensor Short Circuit / PCB Fault
A short circuit involving an NTC temperature sensor or an internal PCB fault. Shared across Vaillant…
High
Engineer
View Guide
F65
Electronics Temperature Too High
The temperature of the PCB electronics itself has exceeded safe operating limits. May indicate an external…
High
Engineer
View Guide
F66
Frost Protection Active
The boiler is running in frost protection mode to prevent freezing.
Medium
DIY
View Guide
F68
Flame Instability
The flame signal is fluctuating, indicating unstable combustion.
High
Engineer
View Guide
F69
CO Sensor — High Reading
The CO sensor has detected elevated carbon monoxide levels in combustion.
High
Engineer
View Guide
F7
DHW Thermistor Fault (Older Ranges)
On older Glow-worm ranges, F7 indicates a domestic hot water thermistor fault.
Medium
Engineer
View Guide
F70
Invalid Device Specific Number (DSN)
The boiler has an invalid or unrecognised device-specific configuration number. Usually occurs after PCB replacement.
Medium
Engineer
View Guide
F71
Flow Sensor Constant Value
The flow sensor is returning the same reading regardless of temperature changes.
Medium
Engineer
View Guide
F72
Flow/Return Delta Too Large
The temperature difference between flow and return is abnormally large.
Medium
Engineer
View Guide
F73
Water Pressure Sensor Signal Too Low
The pressure sensor is reading below its expected range. Could mean genuinely very low pressure or…
High
Engineer
View Guide
F74
Water Pressure Sensor Signal Too High
The pressure sensor is reading above its expected operating range, indicating a faulty sensor or very…
High
Engineer
View Guide
F75
Pump / Pressure Sensor Fault
The boiler cannot detect a pressure change when the pump starts. Because Glow-worm is part of…
Medium
DIY
View Guide
F76
Thermal Fuse Fault (Betacom/Ultracom)
On Glow-worm Betacom and Ultracom models, F76 indicates a thermal fuse fault. The thermal fuse is…
High
Engineer
View Guide
F77
Condensate System Fault / Pump Fault
A fault with the condensate system or pump. On models with a condensate pump, this may…
Medium
Engineer
View Guide
F78
DHW Outlet Sensor Not Bridged
The hot water NTC is not connected or bridged (when an external controller is fitted).
Medium
Engineer
View Guide
F8
Return NTC Sensor Short Circuit
The return water NTC sensor has a short circuit.
Medium
Engineer
View Guide
F80
Condensate Drain Fault
The condensate cannot drain freely, possibly due to a blockage or freeze.
Medium
DIY
View Guide
F82
Pressure Sensor Fault
The electronic water pressure sensor is reading incorrectly.
Medium
Engineer
View Guide
F84
Flow / Return Sensors Transposed
The flow and return temperature sensors appear to be reading inverted values. Usually a post-service issue.
High
Engineer
View Guide
F85
Flow/Return Sensors Same Pipe
Both temperature sensors are fitted to the same pipe.
Medium
Engineer
View Guide
F86
Underfloor Heating Contact Fault
On Glow-worm boilers connected to underfloor heating systems, F86 indicates a fault with the underfloor heating…
Medium
Engineer
View Guide
F9
Pressure Sensor / Low Pressure
The boiler pressure sensor is detecting an issue — either the system pressure is too low,…
Medium
DIY
View Guide
F90
Coding Resistor Mismatch
The coding resistor does not match the gas type setting.
High
Engineer
View Guide
F91
Cylinder Sensor Short Circuit
The hot water cylinder sensor has a short circuit.
Medium
Engineer
View Guide
F92
Gas Type Mismatch
The boiler configuration does not match the connected gas supply.
High
Engineer
View Guide
F93
Combustion Quality Fault
Combustion quality is outside the permitted range.
High
Engineer
View Guide