Protherm
Protherm Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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F0
F0 displayed, furnace does not start heating cycle
Control Board Configuration / Internal Fault
F1
F1 displayed, furnace locked out, no ignition attempt
Flame Detection Circuit Fault (No Flame Signal)
F10
F10 displayed, furnace does not start, display may show low system pressure
Low Water Pressure / Pressure Sensor Fault (Hydronic Protherm Furnace)
F11
F11 displayed, furnace runs briefly then shuts down, may show high pressure
Water Pressure Sensor Range / Signal Error
F12
F12 displayed, furnace unresponsive to thermostat commands
Communication Error Between User Interface and Main PCB
F13
F13 displayed, furnace may run at reduced output or shut down
Outdoor Temperature Sensor Fault (If Fitted)
F14
F14 displayed, furnace will not start, gas valve not energized
Gas Valve Control Fault
F15
F15 displayed, furnace fan runs continuously, no heating
Room Thermostat / Demand Signal Fault
F2
F2 displayed, furnace attempts ignition but shuts down after a few seconds
Flame Loss During Operation
F20
F20 displayed, furnace shuts down with overheat indication
Primary Heat Exchanger Overheat
F22
F22 displayed, furnace will not start, low water pressure warning
Low System Pressure Lockout
F23
F23 displayed, furnace cycles rapidly, poor heating performance
Flow/Return Temperature Difference Too High
F24
F24 displayed, furnace stops shortly after starting, noisy circulation
Water Circulation Fault / Pump Blocked
F25
F25 displayed, furnace shuts down with flue/air fault indication
Flue Gas Recirculation / Poor Combustion
F26
F26 displayed, furnace does not modulate correctly, may lock out
Gas Valve Modulation Fault
F27
F27 displayed, furnace locks out with flame detection error
False Flame Detection / Flame Signal Present When No Flame
F28
F28 displayed, repeated ignition attempts with no flame, then lockout
Ignition Lockout – No Flame
F29
F29 displayed, burner lights then goes out, lockout after several attempts
Flame Loss During Operation
F3
F3 displayed, furnace does not start, fan may run briefly
Ignition Failure (No Flame Established)
F30
F30 displayed, furnace may run in backup mode or shut down
Room Temperature Sensor Fault (Internal or Remote)
F32
F32 displayed, fan speed unstable or not detected correctly
Combustion Fan Speed Sensor Fault
F37
F37 displayed, low water pressure warning, intermittent operation
Low Water Pressure (Warning Level)
F4
F4 displayed, furnace locked out, fan may continue running
Overheat / Safety Thermostat Tripped
F41
F41 displayed, furnace stops with pump/fan synchronization error
Pump or Fan Control Synchronization Fault
F49
F49 displayed, communication error with external controller or bus
eBus / Communication Bus Fault
F5
F5 displayed, furnace will not start, fan may not run
Flow Temperature Sensor Fault (NTC Open/Short)
F6
F6 displayed, furnace cycles erratically or will not modulate correctly
Return Temperature Sensor Fault (NTC Open/Short)
F7
F7 displayed, furnace does not start, fan may run at low speed
Flue Gas Temperature Sensor Fault
F8
F8 displayed, furnace will not ignite, fan may not start
Fan / Air Pressure Switch Fault
F9
F9 displayed, furnace stops and locks out during operation
Flue Gas Overtemperature / Blocked Flue
Symptom
Burning smell or hot plastic odor when furnace runs
Overheating Components / Electrical Overload
Symptom
Condensate drain repeatedly blocks or overflows
Chronic Condensate Drainage Problem
Symptom
Furnace blower runs continuously even when there is no heat demand
Stuck Fan Relay or Incorrect Fan Control Setting
Symptom
Furnace does not start at all, no display, no lights
No Power / Main Fuse or Power Supply Failure
Symptom
Furnace emits a chemical or exhaust‑like smell indoors
Flue Gas Spillage / Incomplete Combustion
Symptom
Furnace is very loud at the flue terminal outside
Excessive Flue Noise / High Gas Rate
Symptom
Furnace makes loud banging or booming noise at startup
Delayed Ignition / Burner Light‑off Problem
Symptom
Furnace produces rumbling or roaring noise during operation
Combustion Instability / Burner Noise
Symptom
Furnace runs but produces no heat, blower runs with cold air
Burner Not Firing / Gas Supply Interruption
Symptom
Furnace short cycles (starts and stops frequently) without reaching set temperature
Short Cycling / Oversized Furnace or Control Issue
Symptom
Furnace starts then shuts down after a few minutes, house never warms up
Limit Switch Trip / Overheat Due to Airflow Restriction
Symptom
Furnace vibrates excessively or rattles during operation
Mechanical Vibration / Loose Components
Symptom
Radiators or hydronic circuits connected to Protherm furnace stay cold while furnace runs
No Circulation in Hydronic Loop
Symptom
System pressure rises excessively when heating and relief valve discharges water
Expansion Vessel Failure / Over‑Pressurization
Symptom
Thermostat calls for heat but furnace starts with long delay or intermittently
Control Logic / Demand Recognition Issue
Symptom
Water leaking from the bottom of the furnace cabinet
Condensate Leak / Internal Water Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| F0 |
F0 displayed, furnace does not start heating cycle
|
Control Board Configuration / Internal Fault | View Details |
| F1 |
F1 displayed, furnace locked out, no ignition attempt
|
Flame Detection Circuit Fault (No Flame Signal) | View Details |
| F10 |
F10 displayed, furnace does not start, display may show low system pressure
|
Low Water Pressure / Pressure Sensor Fault (Hydronic Protherm Furnace) | View Details |
| F11 |
F11 displayed, furnace runs briefly then shuts down, may show high pressure
|
Water Pressure Sensor Range / Signal Error | View Details |
| F12 |
F12 displayed, furnace unresponsive to thermostat commands
|
Communication Error Between User Interface and Main PCB | View Details |
| F13 |
F13 displayed, furnace may run at reduced output or shut down
|
Outdoor Temperature Sensor Fault (If Fitted) | View Details |
| F14 |
F14 displayed, furnace will not start, gas valve not energized
|
Gas Valve Control Fault | View Details |
| F15 |
F15 displayed, furnace fan runs continuously, no heating
|
Room Thermostat / Demand Signal Fault | View Details |
| F2 |
F2 displayed, furnace attempts ignition but shuts down after a few seconds
|
Flame Loss During Operation | View Details |
| F20 |
F20 displayed, furnace shuts down with overheat indication
|
Primary Heat Exchanger Overheat | View Details |
| F22 |
F22 displayed, furnace will not start, low water pressure warning
|
Low System Pressure Lockout | View Details |
| F23 |
F23 displayed, furnace cycles rapidly, poor heating performance
|
Flow/Return Temperature Difference Too High | View Details |
| F24 |
F24 displayed, furnace stops shortly after starting, noisy circulation
|
Water Circulation Fault / Pump Blocked | View Details |
| F25 |
F25 displayed, furnace shuts down with flue/air fault indication
|
Flue Gas Recirculation / Poor Combustion | View Details |
| F26 |
F26 displayed, furnace does not modulate correctly, may lock out
|
Gas Valve Modulation Fault | View Details |
| F27 |
F27 displayed, furnace locks out with flame detection error
|
False Flame Detection / Flame Signal Present When No Flame | View Details |
| F28 |
F28 displayed, repeated ignition attempts with no flame, then lockout
|
Ignition Lockout – No Flame | View Details |
| F29 |
F29 displayed, burner lights then goes out, lockout after several attempts
|
Flame Loss During Operation | View Details |
| F3 |
F3 displayed, furnace does not start, fan may run briefly
|
Ignition Failure (No Flame Established) | View Details |
| F30 |
F30 displayed, furnace may run in backup mode or shut down
|
Room Temperature Sensor Fault (Internal or Remote) | View Details |
| F32 |
F32 displayed, fan speed unstable or not detected correctly
|
Combustion Fan Speed Sensor Fault | View Details |
| F37 |
F37 displayed, low water pressure warning, intermittent operation
|
Low Water Pressure (Warning Level) | View Details |
| F4 |
F4 displayed, furnace locked out, fan may continue running
|
Overheat / Safety Thermostat Tripped | View Details |
| F41 |
F41 displayed, furnace stops with pump/fan synchronization error
|
Pump or Fan Control Synchronization Fault | View Details |
| F49 |
F49 displayed, communication error with external controller or bus
|
eBus / Communication Bus Fault | View Details |
| F5 |
F5 displayed, furnace will not start, fan may not run
|
Flow Temperature Sensor Fault (NTC Open/Short) | View Details |
| F6 |
F6 displayed, furnace cycles erratically or will not modulate correctly
|
Return Temperature Sensor Fault (NTC Open/Short) | View Details |
| F7 |
F7 displayed, furnace does not start, fan may run at low speed
|
Flue Gas Temperature Sensor Fault | View Details |
| F8 |
F8 displayed, furnace will not ignite, fan may not start
|
Fan / Air Pressure Switch Fault | View Details |
| F9 |
F9 displayed, furnace stops and locks out during operation
|
Flue Gas Overtemperature / Blocked Flue | View Details |
| – |
Burning smell or hot plastic odor when furnace runs
|
Overheating Components / Electrical Overload | View Details |
| – |
Condensate drain repeatedly blocks or overflows
|
Chronic Condensate Drainage Problem | View Details |
| – |
Furnace blower runs continuously even when there is no heat demand
|
Stuck Fan Relay or Incorrect Fan Control Setting | View Details |
| – |
Furnace does not start at all, no display, no lights
|
No Power / Main Fuse or Power Supply Failure | View Details |
| – |
Furnace emits a chemical or exhaust‑like smell indoors
|
Flue Gas Spillage / Incomplete Combustion | View Details |
| – |
Furnace is very loud at the flue terminal outside
|
Excessive Flue Noise / High Gas Rate | View Details |
| – |
Furnace makes loud banging or booming noise at startup
|
Delayed Ignition / Burner Light‑off Problem | View Details |
| – |
Furnace produces rumbling or roaring noise during operation
|
Combustion Instability / Burner Noise | View Details |
| – |
Furnace runs but produces no heat, blower runs with cold air
|
Burner Not Firing / Gas Supply Interruption | View Details |
| – |
Furnace short cycles (starts and stops frequently) without reaching set temperature
|
Short Cycling / Oversized Furnace or Control Issue | View Details |
| – |
Furnace starts then shuts down after a few minutes, house never warms up
|
Limit Switch Trip / Overheat Due to Airflow Restriction | View Details |
| – |
Furnace vibrates excessively or rattles during operation
|
Mechanical Vibration / Loose Components | View Details |
| – |
Radiators or hydronic circuits connected to Protherm furnace stay cold while furnace runs
|
No Circulation in Hydronic Loop | View Details |
| – |
System pressure rises excessively when heating and relief valve discharges water
|
Expansion Vessel Failure / Over‑Pressurization | View Details |
| – |
Thermostat calls for heat but furnace starts with long delay or intermittently
|
Control Logic / Demand Recognition Issue | View Details |
| – |
Water leaking from the bottom of the furnace cabinet
|
Condensate Leak / Internal Water Leak | View Details |
No matching codes found
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