Saunier Duval Furnaces Error Codes

F0

Furnace locked out, no heating demand served, display shows F0 and burner does not attempt to ignite

Safety Lockout / Internal Control Fault

F1

Furnace displays F1 and will not start, fan may run briefly then stop, no ignition sequence

Flow Temperature Sensor Fault (NTC Open/Short)

F10

Furnace shows F10, no heating, pump may run briefly then stop

Flow Sensor / Flow Switch Fault

F11

Furnace displays F11, heating stops, may be associated with domestic hot water priority models

DHW Flow Sensor Fault (on combi-type furnace/boiler units)

F12

Furnace shows F12, unit may not respond to user interface commands

User Interface / Display Board Communication Fault

F13

Furnace displays F13, heating may work intermittently, temperature readings appear incorrect

Outdoor Sensor Fault (if fitted) / Auxiliary NTC Fault

F14

Furnace shows F14, burner does not start, may be associated with gas valve control

Gas Valve Control Fault

F15

Furnace displays F15, unit may shut down unexpectedly, sometimes after long operation

Flue Gas Temperature Sensor Fault / Overtemperature

F16

Furnace shows F16, no heating, may occur after power interruptions

Internal EEPROM / Configuration Fault

F2

Furnace shows F2, burner shuts down shortly after starting or does not start, may cycle on/off rapidly

Return Temperature Sensor Fault (NTC Open/Short)

F20

Furnace displays F20, heating stops, pump may continue running

Primary Circuit Overtemperature / Flow Overheat

F22

Furnace shows F22, no heating, may occur after draining or bleeding the system

Dry Fire / Low Water Content Protection

F23

Furnace displays F23, heating stops, may be accompanied by noisy operation

Flow/Return Temperature Differential Too High

F24

Furnace shows F24, rapid temperature rise detected, unit shuts down quickly after start

Pump Blocked / No Circulation

F25

Furnace displays F25, burner shuts down, may be associated with flue gas recirculation

Flue Gas Recirculation / CO Protection

F26

Furnace shows F26, no ignition, may occur after gas valve replacement

Gas Valve Regulation Fault

F27

Furnace displays F27, ignition is blocked, may occur immediately on power-up

Flame Detection Error (False Flame Signal)

F28

Furnace shows F28, repeated ignition attempts with clicking but no flame, then lockout

Ignition Lockout / No Gas Ignition

F29

Furnace displays F29, burner lights briefly then goes out, multiple attempts before lockout

Flame Loss During Operation

F3

Furnace displays F3 and stops, often after running for a short time; casing may feel very hot

Overheat Thermostat Trip / Safety Thermostat Open

F30

Furnace shows F30, no heating, may be associated with room thermostat input

Room Thermostat / External Control Fault

F32

Furnace displays F32, fan speed error, unit may not start or may shut down

Fan Speed Too Low / Fan Control Fault

F37

Furnace shows F37, low system pressure warning, heating may be intermittent

Low Water Pressure

F38

Furnace displays F38, high system pressure warning, safety valve may discharge water

High Water Pressure

F4

Furnace shows F4, no flame established, ignition clicks may be heard but burner does not light

Ignition Failure / No Flame Detection

F41

Furnace shows F41, ignition issues, may be related to incorrect gas type or settings

Incorrect Gas Setting / Combustion Fault

F5

Furnace displays F5, burner shuts down, may occur during operation rather than at startup

Flame Loss During Operation / Flame Signal Fault

F6

Furnace shows F6, fan may run but burner does not light, or unit locks out shortly after start attempt

Air Pressure Switch Fault / Flue Fan Safety

F7

Furnace displays F7, fan may run continuously, burner does not ignite

Fan Speed / Fan Feedback Fault

F8

Furnace shows F8, unit may attempt to start but shuts down quickly, sometimes accompanied by gurgling noises

Low Water Pressure / Water Pressure Sensor Fault

F9

Furnace displays F9, no heating, may occur after power surge or wiring work

External Sensor / Communication Fault

Symptom

Furnace display is on but unresponsive to button presses

Keypad / User Interface Failure

Symptom

Furnace does not start at all, no lights or display, completely dead

No Power / Electrical Supply Failure

Symptom

Furnace emits a burning smell or plastic smell when running

Overheating Component / Electrical Smell

Symptom

Furnace emits a high-pitched whine or humming noise during operation

Fan or Pump Noise / Resonance

Symptom

Furnace fan runs continuously even when there is no heat demand

Fan Overrun / Control Fault

Symptom

Furnace frequently cycles on and off, short burner run times, room temperature unstable

Short Cycling / Oversizing or Control Issue

Symptom

Furnace frequently loses pressure and needs topping up

Chronic Pressure Loss / Leak or Expansion Vessel Failure

Symptom

Furnace makes loud banging or knocking noises when starting or stopping

Water Hammer / Thermal Expansion Noise

Symptom

Furnace runs but radiators remain cold or only lukewarm

Poor Circulation / System Balancing Issue

Symptom

Furnace runs but room never reaches set temperature, especially in cold weather

Underperformance / Sizing or Control Issue

Symptom

Furnace starts then shuts down after a few seconds with a loud whoosh or boom

Delayed Ignition / Burner Light-Back

Symptom

Radiators get hot but domestic hot water temperature is unstable or lukewarm (on combi-type furnace/boiler)

DHW Temperature Control / Plate Heat Exchanger Issue

Symptom

Water dripping from the flue terminal outside

Condensate / Flue Condensation Issue

Symptom

Water leaking from the bottom of the furnace casing

Internal Water Leak