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Updated: November 19, 2024

When it comes to home heating systems, boilers play a crucial role in keeping our homes warm and comfortable. Among the many reputable boiler brands available, Glow-Worm has gained recognition for its reliable and efficient heating solutions. However, like any complex machinery, Glow-Worm boilers can sometimes encounter issues that may disrupt their operation and require troubleshooting.

When it comes to home heating systems, boilers play a crucial role in keeping our homes warm and comfortable. Among the many reputable boiler brands available, Glow-Worm has gained recognition for its reliable and efficient heating solutions. However, like any complex machinery, Glow-Worm boilers can sometimes encounter issues that may disrupt their operation and require troubleshooting.

What are boiler fault codes?

Boiler fault codes are alphanumeric codes that indicate specific issues or faults in a boiler system. These codes are generated by the boiler’s control panel or electronic control unit (ECU) to help diagnose problems and facilitate troubleshooting.

Glow-worm is a British boiler company which has a heating experience of more than 75 years. Glow-worm aim has always been to provide products which are top quality and reliable.

That being said, boilers of top quality do sometimes tend to have certain issues. On this page you will find the error codes or faults of Glow-worm boilers and what they indicate, in addition to possible ways to fix these issues.

Read about: Glow-Worm Boilers Review

A short history of Glow-worm

Glow-worm started producing boilers back in 1934 at the Derwent Foundry in Derbyshire. In 2001, Glow-worm became part of the Vaillant Group. It is worth mentioning that Vaillant is the second-largest heating company in Europe.

Glow-worm manufacturing different gas boilers that include different sizes and types such as combi, system or regular heat-only boilers.

They also state that “it has been the drive which has led us right to the top as one of the leading heating manufacturers in the UK”.

Vaillant has a staff of 12,000 workers across Europe and China. They offer innovative heating, ventilation, air-conditioning technology to countless homes all over the world.

Read more: Common Sime Boiler Error Codes

Main Boiler Error Codes / Fault Codes

Glow-worm Boiler Error Codes

Model of BoilerFault Codes Cause of the Issue
BetacomRed LED OnLockout – low water pressure (increase pressure to 1.5bar) and reset boiler
BetacomRed LED flashingOverheat – check both overheat stats
BetacomYellow LED flashingTurn domestic hot water (DHW) control knob into temperature range and turn central heating (CH) temperature control knob into power (reset position) 
BetacomYellow LED onFlame present on the burner
BetacomGreen LED onGreen LED on
BetacomGreen LED offNo power to boiler – Check for 230volts into the appliance, check the fuse on printed circuit board (PCB)
Betacom4 / Ultracom3 cxi / sxi / 35F00 / F10 / F71Flow heating temperature sensor fault
Betacom4 / Ultracom3 cxi / sxi / 35F01 / F11Return heating temperature sensor fault
Betacom4 / Ultracom3 cxi / sxi / 35F20Overheating fault
Betacom4 / Ultracom3 cxi / sxi / hxi / 35 / Flexicom cx / hx / sxF9 / F22Low water pressure (or ignition temperature rise too slow)
Betacom4 / Ultracom3 cxi / sxi / 35F26 / F77Fault in gas valve
Betacom4 / Ultracom3 cxi / sxi / 35 / CI / hxi / Xtramax HEF27 / F16Flame detection fault
All BoilersF28 / F1 / F4Ignition fault (flame detection)
Betacom4 / Ultracom3 cxi / sxi / 35F29Loss of flame during operation
Betacom4 / Ultracom3 cxi / sxi / 35F32Incorrect air pressure
Betacom4 / Ultracom3 cxi / sxi / 35F49EBUS voltage fault
Betacom4 / Ultracom3 cxi / sxi / 35F61 / F62 / F63 / F64 / F65 / F67Fault in the main board
Betacom4 / Ultracom3 cxi / sxi / 35F68Fluctuation of flame signal
Betacom4 / Ultracom3 cxi / sxi / 35F70User interface incompatible with the main board
Betacom4 / Ultracom3 cxi / sxi / 35F72 / F84Permanent temperature difference between flow and return heating sensors
Betacom4 / Ultracom3 cxi / sxi / 35F73 / F74Heating circuit pressure sensor fault
Betacom4 / Ultracom3 cxi / sxi / 35F76Thermal fuse fault
Betacom4 / Ultracom3 cxi / sxi / 35F83Thermal fuse fault
Betacom4 / Ultracom3 cxi / sxi / 35F85Flow and Return heating sensor fault
Betacom4/ Ultracom3 cxi / sxi / 35F86Underfloor heating contact fault
All BoilersERR / F12 / F18User interface fault
Betacom cTemperature 30 flashingFault on central heating (CH) thermistor
Betacom cTemperature 40 flashingFault on DHW thermistor
Betacom cTemperature 50 flashingFault on outside sensor
Betacom cTemperature 60 flashingLow system pressure
Betacom cTemperature 70 flashingFault on APS
Betacom cTemperature 80 flashingOverheat open circuit
Betacom cTemperature 90 flashingFlame or gas failure
Compact e / sNo DHWCheck dhw microswitch / Check external controls, Please test for 230V on switch live contact
Compact e / sNo C/HCheck dhw microswitch if dhw demand led is lit / Check external controls, Please test for 230V on switch live contact
Compact e / sNo C/H but boiler is firingCheck divertor motor and cartridge / Check external controls, Please test for 230V on switch live contact
Compact e / sBoiler locks out within 10 secondsCheck pump proving switch, air pressure switch and overheat state / Check pump proving switch, air pressure switch and overheat stat
Compact e / sPoor burner pressureCheck burner pressure/ignition adjustment pots on PCB
Ci Range (plus) / Si rangeF2Fan/APS
All BoilersF5Overheat Fault
All BoilersF6Central heating flow thermistor
All BoilersF7Domestic hot water thermistor
All BoilersF8Tank thermistor fault
sxi / si / ci (plus) range / Xtramax HEF9Water pressure sensor fault (please contact GW technical department for further information)
All boilersF10Central return flow thermistor
All boilersF11Main board connection fault
Ci (plus) / cxi / hxi / si / sxi rangeF12Connection fault between main printed circuit board (PCB) and display PCB
Ci (plus) / cxi / hxi / si / sxi rangeF13Main pcb connection fault
Ci (plus) / cxi / hxi / si / sxi rangeF14Central heating flow temperature > 95 degrees
Ci (plus) / cxi / si / sxi rangeF15Gas valve stepper motor fault
Ci (plus) / cxi / hxi / si / sxi range / Xtramax HEF17Power supply is less than 170v
Ci (plus) / cxi / hxi / si / sxi range / Xtramax HEF19Central heating thermistor unplugged
Ci (plus) / cxi / hxi / si / sxi range / Xtramax HEF20Software incompatibility
cxi / hxi / sxi range / Flexicom cxF24Central heating return temperature > 90 degrees
cxi / hxi / sxi / Xtrafast 96/120 / Xtrafast 96/120E1F25 / F26 / F11Poor circulation
ci rangeF3Air fault
cxi / sxi / hxi range/ Xtramax HEF2 / F3Fan
cxi / sxi range / Flexicom cx / hx / sx / hxi / Ultracom cxi / cx / hxi / sxi / Ultrapower sxiF3Fan unable to reach ignition speed
Flexicom cx / hx / sx / hxi / Ultracom cxi / cx / hxi / sxiF9Water pressure sensor fault, blocked flow filter or pump fault
Flexicom cx / hx / sxF11Flow and or return thermistor fault
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HEF13PCB memory or sensing fault
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HEF14Gas valve control defective
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HEF15E-bus voltage failure
All boilersF25 / F23Circulation fault
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxiF43Generic error
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxiF70Software incompatible
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxiF73Unable to see pump activate
Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxiF77Condensate pump error (optional)
hxi rangeF9Earlier models only (please contact GW technical department for further information)
Ultracom? 35 StoreF02 / F12Hot water temperature sensor fault
Ultracom? 35 StoreF03 / F13 / F79Storage tank temperature sensor fault
Ultracom? 35 StoreF81Overheating of hot water circuit
All UltracomNo display or Erloose connection X51
Xtramax HE RangeF24Cental heating return temperature > 90 degrees
Xtramax HE RangeF25Maximum temperature rise slope
Xtramax HE RangeF26Maximum delta temperature
Xtrafast 96/120 RangeF00No-fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF00No-fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF02Airflow fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF05Overheating
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF06Central heating thermistor/wiring fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF08Storage vessel thermistor/wiring fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF09System pressure sensor fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF10Fan fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF13Main printed circuit board (PCB) fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF14Central heating flow temperature > 97 degrees
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF15Gas mechanism fault
Xtrafast 96/120 Range / Xtrafast 96/120E1 RangeF20Communication fault

Read about: Ferroli Boiler Error Codes / Fault codes List

Biasi Boiler Error Codes / Fault Codes 

Glow-worm Energy boiler range error codes

Fault CodeCause of the Issue
F.00Flow temperature sensor
F.10Flow temperature sensor short circuit
F.12 and F.91Cylinder temperature sensor short circuit
F.13Domestic hot water cylinder temperature sensor short circuit
F.20Safety switch-off – overheating temperature reached
F.22Safety switch-off – low water pressure in the boiler
F.23Safety switch-off – temperature difference too great (NTC1/NTC2)
F.24Safety switch-off – temperature rise too fast
F.25Safety switch-off – flue gas temperature too high
F.27Safety switch-off – fault in flame detection
F.28Ignition unsuccessful when starting up
F.29Flame loss
F.32Fan frost protection function active – fan speed outside the tolerance values
F.33Fan frost protection function active – air pressure switch fault
FA9eBUS fault – voltage too low
F.61Gas valve control system fault
F.82Gas valve switch-off control fault
F.83EEPROM fault – electronics defective
F.64Electronics/sensor/analogue-to-digital converter fault
F.85Electronics temperature too high
F.67Value sent back by ASIC is incorrect (flame signal)
F.88Unstable flame (analogue input), underfloor heating contact or gas valve fault
F.70Invalid product code (DSN)
F.71Flow/return temperature sensor
F.72Deviation in the water pressure sensor/return temperature sensor
F.73Water pressure sensor not connected or has short-circuited
F.74Electrical problem in the water pressure sensor
F.75Pressure sensor fault
F.78The safety cut-out in the primary heat exchanger is defective
F.77Fault: Condensate or smoke
F.78Interruption to domestic hot water (DHW) outlet sensor at external controller
F.83Burner temperature sensor fault
F.84Flow/return temperature sensor fault
F.85Temperature sensor fault
F.87Electrodes fault
F.89Pump fault
ConnectionNo communication between the printed circuit board (PCB) and the user interface

Read more: Biasi Boiler Error Codes / Fault Codes 

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FAQs

How long will a Glow Worm boiler last?

A good quality boiler is expected to last around 10 to 15 years.

Are Glow Worm and Vaillant the same company?

In 2001 Glow-worm was acquired by the Vaillant Group.

How efficient are Glow Worm boilers?

In terms of energy efficiency, all of the Glow Worm regular boilers are B-rated, varying between 89.3 – 89.7% (nearly A-rated) with the exception of the Easicom 3, which is 94% energy efficient.

Are Glow-worm boilers condensing?

Yes. Glow-worm is a trusted manufacturer of high-efficiency combi and condensing boilers.