Immergas
Immergas Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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01
Furnace does not ignite, burner never lights, display shows 01 lockout
Ignition Failure / No Flame Detection
02
Furnace locks out shortly after ignition attempt, display shows 02, burner lights briefly then goes out
Flame Loss During Operation
03
Furnace attempts to start, fan runs but burner does not ignite, display shows 03
Flue Gas Exhaust / Fan Fault
04
Furnace stops and displays 04, often after overheating, radiators very hot, burner off
Primary Flow Overtemperature / Safety Thermostat Tripped
05
Furnace shows 05, burner does not start, fan may run briefly then stop
Air Pressure Switch / Flue Safety Fault
06
Display shows 06, furnace does not start, may occur immediately on power-up
Flow Temperature Sensor (NTC) Fault
07
Display shows 07, furnace may run at reduced power or stop, temperature readings are erratic
Return Temperature Sensor (NTC) Fault
08
Furnace shows 08, domestic hot water (DHW) may not function correctly or temperature fluctuates
DHW Temperature Sensor (NTC) Fault
09
Display shows 09, furnace does not respond to room thermostat or external controls
External Control / Thermostat Circuit Fault
10
Furnace shows 10, no heating or DHW, may occur after power surge
General Electronic Board Fault
11
Display shows 11, furnace does not start, may be associated with low system pressure
Water Pressure Switch / Sensor Fault
12
Furnace shows 12, burner shuts down, may be accompanied by loud boiling noises
Primary Circuit Overheat / Limit Thermostat Intervention
13
Display shows 13, furnace may run at reduced output or stop intermittently
Flue Gas Temperature Sensor Fault
14
Furnace shows 14, burner stops, may be associated with condensate issues
Condensate Drain Fault
15
Display shows 15, furnace does not start, may be related to gas valve control
Gas Valve Control Fault
20
Furnace shows 20, no operation, may be after incorrect wiring or power event
Phase / Neutral / Earth Wiring Fault
21
Display shows 21, boiler may lock out randomly, sometimes after thermostat or bus wiring changes
Communication Fault with Remote Controller / Bus
27
Furnace shows 27, burner output limited or boiler stops, often in condensing models
Flue Gas Overtemperature
28
Display shows 28, boiler may not modulate correctly, unstable operation
Fan Speed Control / Tachometer Fault
31
Furnace shows 31, no ignition, may be associated with ionization issues
Ionization Circuit Fault
37
Display shows 37, boiler may not start or may shut down unexpectedly
Safety Thermostat / Overheat Cut-out Fault
40
Furnace shows 40, no operation, may be related to fan proving or air pressure
Air Pressure Switch Stuck or Not Changing State
41
Display shows 41, boiler may start and stop rapidly, unstable heating
Flow Sensor / Flow Switch Fault (DHW or Heating)
50
Furnace shows 50, burner output limited, may be related to gas type or calibration
Gas Valve Calibration / Configuration Error
51
Display shows 51, boiler may not reach set temperature, poor modulation
Modulation Control Fault
60
Furnace shows 60, no heating, may be associated with external safety devices
External Safety Device Intervention (e.g., flue thermostat, safety chain)
70
Display shows 70, boiler may operate but with incorrect temperatures or strange behavior
Parameter / Configuration Error
Symptom
Domestic hot water temperature fluctuates between hot and cold during use
Inconsistent DHW Temperature
Symptom
Furnace does not start at all, display is blank or dead
No Power / Dead Appliance
Symptom
Furnace emits a burning smell or plastic odor when running
Overheating Components / Electrical Smell
Symptom
Furnace fan runs but burner does not ignite, no error code displayed
Ignition Sequence Interruption
Symptom
Furnace frequently cycles on and off, radiators get hot quickly then cool, short cycling
Short Cycling / Oversized Boiler or Poor Control Strategy
Symptom
Furnace is very noisy during operation, with humming, whistling, or droning sounds
Combustion or Mechanical Noise
Symptom
Furnace leaks water from underneath the casing
Internal Water Leak
Symptom
Furnace makes loud banging or knocking noises when starting or stopping
Water Hammer / Thermal Expansion Noise
Symptom
Furnace runs but radiators stay lukewarm, house does not reach set temperature
Insufficient Heating Output / Under-sizing or Modulation Issue
Symptom
Furnace starts but shuts down after a few seconds without showing a specific error code
Unstable Flame / Early Shutdown
Symptom
Radiators get hot even when the room thermostat is not calling for heat
Heating Running Continuously / Control Fault
Symptom
System pressure drops over time, requiring frequent topping up
Chronic Pressure Loss / Leak
Symptom
System pressure rises rapidly when heating and relief valve discharges water
Over-pressurization / Expansion Vessel Failure
Symptom
Water is dripping from the condensate pipe or flue joint area inside the boiler
Condensate Leakage / Flue Seal Failure
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 01 |
Furnace does not ignite, burner never lights, display shows 01 lockout
|
Ignition Failure / No Flame Detection | View Details |
| 02 |
Furnace locks out shortly after ignition attempt, display shows 02, burner lights briefly then goes out
|
Flame Loss During Operation | View Details |
| 03 |
Furnace attempts to start, fan runs but burner does not ignite, display shows 03
|
Flue Gas Exhaust / Fan Fault | View Details |
| 04 |
Furnace stops and displays 04, often after overheating, radiators very hot, burner off
|
Primary Flow Overtemperature / Safety Thermostat Tripped | View Details |
| 05 |
Furnace shows 05, burner does not start, fan may run briefly then stop
|
Air Pressure Switch / Flue Safety Fault | View Details |
| 06 |
Display shows 06, furnace does not start, may occur immediately on power-up
|
Flow Temperature Sensor (NTC) Fault | View Details |
| 07 |
Display shows 07, furnace may run at reduced power or stop, temperature readings are erratic
|
Return Temperature Sensor (NTC) Fault | View Details |
| 08 |
Furnace shows 08, domestic hot water (DHW) may not function correctly or temperature fluctuates
|
DHW Temperature Sensor (NTC) Fault | View Details |
| 09 |
Display shows 09, furnace does not respond to room thermostat or external controls
|
External Control / Thermostat Circuit Fault | View Details |
| 10 |
Furnace shows 10, no heating or DHW, may occur after power surge
|
General Electronic Board Fault | View Details |
| 11 |
Display shows 11, furnace does not start, may be associated with low system pressure
|
Water Pressure Switch / Sensor Fault | View Details |
| 12 |
Furnace shows 12, burner shuts down, may be accompanied by loud boiling noises
|
Primary Circuit Overheat / Limit Thermostat Intervention | View Details |
| 13 |
Display shows 13, furnace may run at reduced output or stop intermittently
|
Flue Gas Temperature Sensor Fault | View Details |
| 14 |
Furnace shows 14, burner stops, may be associated with condensate issues
|
Condensate Drain Fault | View Details |
| 15 |
Display shows 15, furnace does not start, may be related to gas valve control
|
Gas Valve Control Fault | View Details |
| 20 |
Furnace shows 20, no operation, may be after incorrect wiring or power event
|
Phase / Neutral / Earth Wiring Fault | View Details |
| 21 |
Display shows 21, boiler may lock out randomly, sometimes after thermostat or bus wiring changes
|
Communication Fault with Remote Controller / Bus | View Details |
| 27 |
Furnace shows 27, burner output limited or boiler stops, often in condensing models
|
Flue Gas Overtemperature | View Details |
| 28 |
Display shows 28, boiler may not modulate correctly, unstable operation
|
Fan Speed Control / Tachometer Fault | View Details |
| 31 |
Furnace shows 31, no ignition, may be associated with ionization issues
|
Ionization Circuit Fault | View Details |
| 37 |
Display shows 37, boiler may not start or may shut down unexpectedly
|
Safety Thermostat / Overheat Cut-out Fault | View Details |
| 40 |
Furnace shows 40, no operation, may be related to fan proving or air pressure
|
Air Pressure Switch Stuck or Not Changing State | View Details |
| 41 |
Display shows 41, boiler may start and stop rapidly, unstable heating
|
Flow Sensor / Flow Switch Fault (DHW or Heating) | View Details |
| 50 |
Furnace shows 50, burner output limited, may be related to gas type or calibration
|
Gas Valve Calibration / Configuration Error | View Details |
| 51 |
Display shows 51, boiler may not reach set temperature, poor modulation
|
Modulation Control Fault | View Details |
| 60 |
Furnace shows 60, no heating, may be associated with external safety devices
|
External Safety Device Intervention (e.g., flue thermostat, safety chain) | View Details |
| 70 |
Display shows 70, boiler may operate but with incorrect temperatures or strange behavior
|
Parameter / Configuration Error | View Details |
| – |
Domestic hot water temperature fluctuates between hot and cold during use
|
Inconsistent DHW Temperature | View Details |
| – |
Furnace does not start at all, display is blank or dead
|
No Power / Dead Appliance | View Details |
| – |
Furnace emits a burning smell or plastic odor when running
|
Overheating Components / Electrical Smell | View Details |
| – |
Furnace fan runs but burner does not ignite, no error code displayed
|
Ignition Sequence Interruption | View Details |
| – |
Furnace frequently cycles on and off, radiators get hot quickly then cool, short cycling
|
Short Cycling / Oversized Boiler or Poor Control Strategy | View Details |
| – |
Furnace is very noisy during operation, with humming, whistling, or droning sounds
|
Combustion or Mechanical Noise | View Details |
| – |
Furnace leaks water from underneath the casing
|
Internal Water Leak | View Details |
| – |
Furnace makes loud banging or knocking noises when starting or stopping
|
Water Hammer / Thermal Expansion Noise | View Details |
| – |
Furnace runs but radiators stay lukewarm, house does not reach set temperature
|
Insufficient Heating Output / Under-sizing or Modulation Issue | View Details |
| – |
Furnace starts but shuts down after a few seconds without showing a specific error code
|
Unstable Flame / Early Shutdown | View Details |
| – |
Radiators get hot even when the room thermostat is not calling for heat
|
Heating Running Continuously / Control Fault | View Details |
| – |
System pressure drops over time, requiring frequent topping up
|
Chronic Pressure Loss / Leak | View Details |
| – |
System pressure rises rapidly when heating and relief valve discharges water
|
Over-pressurization / Expansion Vessel Failure | View Details |
| – |
Water is dripping from the condensate pipe or flue joint area inside the boiler
|
Condensate Leakage / Flue Seal Failure | View Details |
No matching codes found
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