Main Heating is a UK boiler brand that is part of BDR Thermea, the same group as Baxi and Potterton. Their boilers share many components and fault codes with Baxi. The Main Eco Compact range is a popular, space-saving combi boiler commonly found in flats and smaller properties.
Main Heating Boiler Fault Codes
All Main Heating Fault Codes 41
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| E09 | Gas Valve Connection Error On Main Eco Compact boilers, code E09 indicates a fault in the gas valve connection… | High | Engineer | View Guide |
| E10 | DHW NTC Fault Hot water sensor faulty. | Medium | Engineer | View Guide |
| E109 | Pre-Circulation Fault The boiler has detected insufficient circulation during its pre-circulation check. | Medium | Engineer | View Guide |
| E11 | Return NTC Fault Return sensor faulty. | Medium | Engineer | View Guide |
| E110 | Overheat Lockout The boiler has overheated and the safety thermostat has triggered. | High | Engineer | View Guide |
| E119 | Low Water Pressure System pressure has dropped below 0.5 bar. Main Heating boilers share the same fault code… | Low | DIY Check | View Guide |
| E12 | Flow NTC Short Circuit Flow sensor shorted. | Medium | Engineer | View Guide |
| E125 | Primary Circuit Circulation Fault Insufficient water circulation through the primary heating circuit. | Medium | Engineer | View Guide |
| E128 | Loss of Flame During Operation The boiler has lost its flame 12 times during operation, triggering a safety lockout. | High | Engineer | View Guide |
| E13 | Return NTC Short Circuit Return sensor shorted. | Medium | Engineer | View Guide |
| E130 | Flue Thermostat Tripped The flue safety thermostat has activated due to excessively high flue temperatures. | High | Engineer | View Guide |
| E133 | Ignition Failure / Frozen Condensate The boiler has failed to ignite. Identical to Baxi E133 — Main Heating shares the… | Medium | DIY Check | View Guide |
| E135 | Gas Supply Interruption The gas supply to the boiler has been interrupted. | Medium | DIY Check | View Guide |
| E14 | DHW NTC Short Circuit DHW sensor shorted. | Medium | Engineer | View Guide |
| E15 | Diverter Valve Fault Valve stuck or not switching. | Medium | Engineer | View Guide |
| E154 | Flow/Return Sensor Test Failure The boiler's internal sensor cross-check test has failed. | Medium | Engineer | View Guide |
| E16 | Condensate Blocked Condensate pipe blocked. | Medium | DIY Check | View Guide |
| E160 | Fan Fault The boiler fan has a fault — not running, running slowly, or speed sensor failure. | High | Engineer | View Guide |
| E168 | PCB Lockout / Unspecified Fault The PCB has detected an unspecified fault and locked out the boiler. | High | Engineer | View Guide |
| E17 | Fan Fault Fan not running correctly. | High | Engineer | View Guide |
| E18 | Gas Valve Fault Gas valve not responding. | High | Engineer | View Guide |
| E19 | Pump Fault Pump not running. | High | Engineer | View Guide |
| E20 | CH NTC Sensor Fault Central heating thermistor sensor fault on Main Heating boilers. | Medium | Engineer | View Guide |
| E21 | PCB Fault Internal PCB error. | High | Engineer | View Guide |
| E22 | Low Gas Pressure Gas pressure too low. | High | Engineer | View Guide |
| E23 | Air Pressure Switch APS fault. | High | Engineer | View Guide |
| E24 | Flame Instability Flame signal fluctuating. | High | Engineer | View Guide |
| E25 | Overheat Protection Safety thermostat activated. | High | Engineer | View Guide |
| E26 | Rapid Temperature Rise Flow temp rising too fast. | High | Engineer | View Guide |
| E27 | Pressure Sensor Fault Electronic sensor faulty. | Medium | Engineer | View Guide |
| E270 | Dry Fire Detected The boiler has fired without adequate water circulation — a dry fire condition. | High | Engineer | View Guide |
| E28 | Frozen Condensate / Flue Thermistor Fault In cold weather, E28 on Main Heating boilers indicates a frozen condensate pipe. In warmer… | Medium | DIY Check | View Guide |
| E30 | Frost Protection Active Frost protection running. | Medium | DIY Check | View Guide |
| E31 | eBUS Fault Communication fault. | Medium | Engineer | View Guide |
| E32 | Combustion Fault Air/gas mixture outside limits. | High | Engineer | View Guide |
| E321 | Hot Water NTC Fault (Eco Compact) On Main Eco Compact boilers, E321 indicates a hot water thermistor fault. | Medium | Engineer | View Guide |
| E384 | False Flame Detected The boiler is detecting a flame signal when the gas valve should be closed. | High | Engineer | View Guide |
| E40 | CH Return Sensor Error Central heating return sensor has a fault on Main Eco Compact boilers. | Medium | Engineer | View Guide |
| E50 | Hot Water NTC Fault The domestic hot water temperature sensor has a fault on Main Heating boilers. | Medium | Engineer | View Guide |
| E60 | Fan or Fan Wiring Fault On some older Main boilers, E60 indicates a fan or fan wiring fault. | High | Engineer | View Guide |
| E83 | Communication Error A communication error between the boiler PCB and external controls or room controller. | Medium | Engineer | View Guide |