Protherm Fault Codes

Select a fault code to see its meaning, common causes and how to fix it.

E1 On Protherm boilers, the E1 fault code signals a flue gas extraction or air pressure error. This is not the same as the… Read more →
E2 The E2 fault code on a Protherm boiler indicates that the control board has detected a problem with the heating circuit… Read more →
E3 The E3 code appears on Protherm boilers when the electronic control unit detects a problem with the domestic hot water… Read more →
E4 The E4 fault code on a Protherm boiler indicates that the heat exchanger has reached an unsafe temperature —… Read more →
E6 The E6 code on a Protherm boiler signals that the appliance has attempted to light its burner but failed to establish… Read more →
E7 The E7 code (sometimes displayed as Eb on certain Protherm models) indicates that the boiler's control board has… Read more →
EP The EP fault code on a Protherm boiler indicates a heating circuit error. The boiler's control unit continuously… Read more →
F.0 The F.0 fault code (also shown as F0) on Protherm boilers indicates that the heating circuit water pressure has dropped… Read more →
F.00 The F.00 code appears on Protherm boilers when the electronic control unit stops receiving a valid signal from the… Read more →
F.01 The F.01 code on a Protherm boiler indicates that the return temperature sensor — known as NTC5 — is either reading an… Read more →
F.02 The Protherm F.02 (also displayed as F2) fault code points to a problem with the heating circuit flow NTC thermistor —… Read more →
F.03 The F.03 code on a Protherm boiler has two distinct meanings depending on which model range you own. On Gepard and… Read more →
F.04 The F.04 code appears on Protherm boilers when the control board detects a short circuit in the domestic hot water… Read more →
F.05 The F.05 (or F5) fault code on a Protherm boiler has two distinct meanings depending on which model you own. On most… Read more →
F.06 The F.06 fault code on a Protherm boiler signals that the control unit has detected an abnormal or missing signal from… Read more →
F.07 The F.07 code appears on Protherm boilers when the flame monitoring system detects a problem confirming that a flame is… Read more →
F.08 The F.08 code appears on Protherm boilers — including the Gepard, Panther, Puma Condens, Lynx Condens, and Medved… Read more →
F.09 The F.09 fault code on Protherm boilers signals a problem with the fan and air pressure switch (pressostat) sequencing.… Read more →
F.1 The Protherm F.1 fault code indicates a safety lockout, but crucially its precise meaning depends on which Protherm… Read more →
F.10 The F.10 fault code on most Protherm boilers — particularly the Gepard (Cheetah) range — points to a short circuit… Read more →
F.11 The F.11 fault code on Protherm boilers indicates that the control board has detected a short circuit or open circuit… Read more →
F.12 The F.12 fault code on most Protherm boilers indicates that the domestic hot water (DHW) temperature sensor has… Read more →
F.13 The F.13 code appears on Protherm boilers when the control system detects a problem with the domestic hot water (DHW)… Read more →
F.14 The F.14 code appears on Protherm boilers (including the Gepard, Panther, and Condens ranges) when the control board… Read more →
F.15 The F.15 fault code on a Protherm boiler points to a problem with the boiler's fan or its flue exhaust gas sensing… Read more →
F.16 The F.16 code appears on Protherm boilers when the control board detects a short circuit in the flue draught sensor… Read more →
F.17 The F.17 code appears on Protherm boilers — most notably the Gepard (Cheetah) series fitted with a solar thermal system… Read more →
F.18 The F.18 code appears on Protherm boilers when the control system detects a short circuit in the NTC temperature sensor… Read more →
F.19 The F.19 fault code on a Protherm boiler indicates that the control board has detected a short circuit in the exhaust… Read more →
F.2 The F.2 code on Protherm boilers signals that the control board has lost a valid reading from the heating circuit flow… Read more →
F.20 The F.20 code appears when Protherm's built-in safe temperature limiter detects that the primary circuit flow… Read more →
F.21 The F.21 fault code on Protherm boilers (including the Gepard series) indicates a safety lockout triggered because one… Read more →
F.22 The F.22 fault code on Protherm boilers signals that the water pressure in your sealed heating system has fallen too… Read more →
F.23 The F.23 code on Protherm boilers signals that the temperature gap between the flow pipe (hot water leaving the boiler)… Read more →
F.24 The F.24 fault code on Protherm boilers indicates that the boiler's PCB has detected an abnormally rapid rise in water… Read more →
F.25 The F.25 fault code on Protherm boilers is a safety lockout that can have two related meanings depending on your model.… Read more →
F.26 The F.26 fault code on a Protherm boiler indicates that the control board has detected an incorrect or absent signal… Read more →
F.27 The F.27 code means your Protherm boiler has detected a flame signal at a point when it shouldn't exist — or the flame… Read more →
F.28 The F.28 code appears on Protherm boilers — including the Gepard and Panther ranges — when the burner fails to light on… Read more →
F.29 The F.29 code appears on Protherm boilers when the appliance detects that a flame has been lost — or could not be… Read more →
F.30 The F.30 code appears on Protherm boilers — displayed as a flashing 'F' alongside the number 30 — when the boiler's… Read more →
F.31 The F.31 code appears on Protherm boilers when the control board detects a short circuit in the lock-out sensor… Read more →
F.32 The F.32 code appears on Protherm boilers when the ventilator (fan) is detected running outside its acceptable speed… Read more →
F.33 The F.33 code on a Protherm boiler indicates that the air pressure switch — also called the differential relay or… Read more →
F.35 The F.35 code tells you that your Protherm boiler has detected a fault within its flue or combustion exhaust system. In… Read more →
F.36 The F.36 code appears on chimney-type (open-flue, natural draught) Protherm boilers when the boiler's internal safety… Read more →
F.37 The F.37 code appears on Protherm boilers when the pressure-monitoring circuit detects that water pressure in the… Read more →
F.38 The F.38 code appears on Protherm boilers when the control board (PCB) detects that a measured frequency signal falls… Read more →
F.39 The F.39 fault code indicates that the Protherm boiler's electronic control board (PCB) has been unable to correctly… Read more →
F.41 The F.41 code appears on Protherm boilers when the control board (PCB) attempts to open an internal gas regulation… Read more →
F.42 The F.42 code appears on Protherm boilers when the control board detects that the coding resistor (R1) is returning a… Read more →
F.43 The F.43 fault code appears on Protherm boilers when the control board is unable to identify or confirm which boiler… Read more →
F.49 The F.49 code on a Protherm boiler indicates that the boiler's internal eBUS communication system is reporting an… Read more →
F.55 The F.55 code appears on Protherm boilers when the built-in carbon monoxide (CO) sensor has detected a fault — either… Read more →
F.58 The F.58 fault code indicates that the boiler's control board (PCB) has sent an activation signal to the preheater —… Read more →
F.60 The F.60 code on Protherm boilers signals a fault on the positive side of the gas valve control circuit — in other… Read more →
F.61 The F.61 code appears on Protherm boilers when the control board (PCB) cannot correctly communicate with or actuate the… Read more →
F.62 The F.62 code on a Protherm boiler indicates that the gas valve has not closed within the expected timeframe after the… Read more →
F.63 The F.63 code appears on Protherm boilers when the main printed circuit board (PCB) has detected a problem with its… Read more →
F.64 The F.64 code appears on Protherm boilers when the control board detects an ADC (Analogue-to-Digital Converter) error —… Read more →
F.65 The F.65 code on Protherm boilers indicates that the main control board (PCB) has detected its own temperature is too… Read more →
F.66 The F.66 code sits within the F.60–F.67 electronics and gas valve control block on Protherm boilers. This group of… Read more →
F.67 The F.67 code appears when the boiler's control electronics receive a flame signal that is absent, unreadable, or… Read more →
F.70 The F.70 code means the boiler has detected an invalid or missing Device Specific Number (DSN) — essentially, the main… Read more →
F.71 The F.71 fault code appears on Protherm boilers when the control board detects that the flow temperature sensor (the… Read more →
F.72 The F.72 code appears on Protherm boilers when the control board detects a persistent, abnormal difference between the… Read more →
F.73 The F.73 fault code on a Protherm boiler indicates that the central heating water pressure sensor is either not… Read more →
F.74 The F.74 fault code indicates that the boiler's central heating (CH) water pressure sensor is producing an electrical… Read more →
F.75 The F.75 fault code appears when the boiler's pressure sensor fails to detect any change in water pressure after the… Read more →
F.76 The F.76 code appears when the boiler's thermal overheating protection triggers a safety shutdown on the primary heat… Read more →
F.80 The F.80 code appears on Protherm boilers when the control board detects a fault with the temperature sensor monitoring… Read more →
F.81 The F.81 code on Protherm boilers signals a fault with the charger pump — the secondary circulation pump responsible… Read more →
F.82 The F.82 code appears on Protherm boilers — most notably the Gepard and Panther KTV storage-combi models — when the… Read more →
F.90 The F.90 code appears on Protherm boilers when the control board cannot detect the APC (Accessory/Peripheral Control)… Read more →
F.91 The F.91 fault code on a Protherm boiler signals a problem with the APC (Automatic Pump Control) module's NTC… Read more →
F3 The Protherm F3 fault code has two distinct meanings depending on your specific model. On the most widely sold Protherm… Read more →
F5 The F5 code on most Protherm boilers — including the Panther, Leopard, and Gepard — signals a problem with the outdoor… Read more →
F9 The F9 fault code on Protherm boilers signals that something has interrupted the boiler's safe operation — but what… Read more →