Glow-worm · An established brand in the UK. 120 codes across 1 product family, each taken from the manufacturer’s manuals. Glow-worm technical support ↗
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Type the code on your display or a word from its meaning. Each code opens its own page with what it means, whether it is safe and what you can check.
120 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| F.022 | No/insufficient water in the product or the water pressure is too low | Yes | Yes |
| F.042 | The coding resistor (in the wiring harness) or the gas group resistor (on the PCB, if available) is invalid | Yes | Yes |
| F.070 | Invalid Device Specific Number (referenced with F.042: heat cell coding resistor not detected) | Yes | Yes |
| F.283 | De-icing was unsuccessful | Yes | Yes |
| F.514 | Invalid compressor inlet temperature sensor signal | Yes | Yes |
| F.517 | Invalid compressor outlet temperature sensor signal | Yes | Yes |
| F.519 | Building circuit return temperature sensor signal invalid | Yes | Yes |
| F.520 | Building circuit flow temperature sensor signal invalid | Yes | Yes |
| F.526 | The signal for the temperature sensor at the evaporator inlet in the refrigerant circuit is invalid | Yes | Yes |
| F.546 | Refrigerant circuit high-pressure sensor signal invalid | Yes | Yes |
| F.582 | A fault has been detected in the connection of the electric expansion valve | Yes | Yes |
| F.585 | The signal for the temperature sensor at the condenser outlet in the refrigerant circuit is invalid | Yes | Yes |
| F.703 | Refrigerant circuit low-pressure sensor signal invalid | Yes | Yes |
| F.718 | Environment circuit fan 1 is blocked | Yes | Yes |
| F.729 | The temperature at the compressor outlet is lower than the condensation temperature | Yes | Yes |
| F.731 | High-pressure switch has been triggered | Yes | Yes |
| F.732 | Compressor outlet temperature too high | Yes | Yes |
| F.733 | Evaporation temperature too low | Yes | Yes |
| F.734 | Condensation temperature too low | Yes | Yes |
| F.735 | Evaporation temperature too high | Yes | Yes |
| F.737 | The condensation temperature in the refrigerant circuit is too high | Yes | Yes |
| F.739 | Refrigerant mass too low | Yes | Yes |
| F.752 | The frequency inverter reports an internal fault or an unknown compressor fault | Yes | Yes |
| F.753 | The communication with the frequency inverter has been interrupted | Yes | Yes |
| F.755 | The 4-port diverter valve is not in the expected position | Yes | Yes |
| F.757 | During heat pump mode, the compressor running time fell below the minimum level too frequently | Yes | Yes |
| F.764 | The internal inverter diagnostics report a compressor phase error | Yes | Yes |
| F.785 | Environment circuit fan 2 is blocked | Yes | Yes |
| F.788 | Building circuit pump reports internal faults | Yes | Yes |
| F.817 | The inverter reports a fault in the compressor motor | Yes | Yes |
| F.818 | The mains voltage at the frequency inverter is not available or outside of the tolerances | Yes | Yes |
| F.819 | The frequency inverter has overheated | Yes | Yes |
| F.820 | The communication with the building circuit pump has been interrupted | Yes | Yes |
| F.821 | Electric back-up heater flow temperature sensor signal invalid | Yes | Yes |
| F.822 | The pressure sensor for the brine in the building circuit has been interrupted or has short-circuited | Yes | Yes |
| F.823 | Compressor temperature switch has triggered | Yes | Yes |
| F.824 | Decoupling module (frost protection) brine circuit pressure too low | Yes | Yes |
| F.825 | The signal for the temperature sensor at the condenser inlet in the refrigerant circuit is invalid | Yes | Yes |
| F.827 | The signal for the water pressure sensor in the building circuit is invalid | Yes | Yes |
| F.905 | Communication interface switched off | Yes | Yes |
| F.1117 | Frequency inverter phase failure | Yes | Yes |
| F.9997 | Communication between the indoor unit and outdoor unit is not possible due to the different versions of the bus protocol | Yes | Yes |
| F.9998 | No communication is possible between the indoor unit and the outdoor unit | Yes | Yes |
| I.003 | The maintenance time has been reached | No | Yes |
| I.032 | Building circuit water pressure low | No | Yes |
| I.200 | Low pressure in the decoupled brine circuit (building circuit) - systems with decoupled brine circuit | No | Yes |
| I.201 | Signal for the cylinder temperature sensor is invalid | No | Yes |
| I.202 | Signal for the system temperature sensor invalid | No | Yes |
| I.203 | No communication between the display and the main PCB | No | Yes |
| L.250 | The target speed for fan 1 not reached. | Partly | Yes |
| L.251 | The target speed for fan 2 not reached. | Partly | Yes |
| L.271 | Outside of normal operating mode: Building circuit volume flow too low | Partly | Yes |
| L.275 | The volume flow in the building circuit is too low during de-icing. | Partly | Yes |
| L.283 | De-icing unsuccessful. The unit attempts to restart. | Partly | Yes |
| L.284 | The flow temperature in the building circuit during de-icing is too low. The unit attempts to restart. | Partly | Yes |
| L.302 | The high-pressure switch in the refrigerant circuit has been triggered. | Partly | Yes |
| L.718 | Fan 1 from the environment circuit is not rotating. The heat pump attempts to restart the fan. | Partly | Yes |
| L.745 | Outside of normal operation: Setting for building circuit volume flow too high | Partly | Yes |
| L.752 | The frequency inverter reports an internal fault or an unknown compressor fault. The unit attempts to restart. | Partly | Yes |
| L.753 | The communication with the frequency inverter has been interrupted. | Partly | Yes |
| L.755 | The 4-port diverter valve is not in the expected position. The unit attempts a restart. | Partly | Yes |
| L.757 | The heat pump has fallen below the minimum running time for the compressor. The unit continues to operate. If the minimum running time is repeatedly not reached, operation is stopped in order to protect the compressor. | Partly | Yes |
| L.764 | Inverter reports compressor phase fault | Partly | Yes |
| L.785 | Fan 2 from the environment circuit is not rotating. The heat pump attempts to restart the fan. | Partly | Yes |
| L.788 | The building circuit pump reports an internal fault. The unit attempts to restart. | Partly | Yes |
| L.817 | The inverter reports a fault in the compressor motor. The unit attempts to restart. | Partly | Yes |
| L.818 | The mains voltage is not available or is outside of the tolerances. The unit attempts to restart. | Partly | Yes |
| L.819 | The frequency inverter has overheated. The unit attempts a restart. | Partly | Yes |
| L.823 | The temperature switch at the compressor head or compressor outlet has triggered because the hot gas temperature is too high. The unit attempts to restart. | Partly | Yes |
| N.200 | Invalid signal for outdoor unit temperature sensor for the air inlet | Partly | Yes |
| N.521 | Outdoor temperature sensor signal invalid | Partly | Yes |
| N.685 | System control communication interrupted | Partly | Yes |
| S.34 | Heating mode: Frost protection If the measured outdoor temperature falls below XX °C, the temperature of the heating circuit's flow and return is monitored. If the temperature difference exceeds the set value, the pump and compressor are started without a heat demand. | No | Yes |
| S.91 | Service message: Demo mode | No | Yes |
| S.100 | Unit in standby There is no heat demand or cooling demand. Standby 0: Outdoor unit. Standby 1: Indoor unit | No | Yes |
| S.101 | Heating mode: Compressor switched off The heat demand is met, the demand is ended by the system control and the heat deficit is offset. The compressor is switched off. | No | Yes |
| S.102 | Heating mode: Compressor blocked The compressor is blocked for heating mode because the heat pump is outside of its application limits. | Partly | Yes |
| S.103 | Heating mode: Pump prerun The start conditions for the compressor in heating mode are checked. Start the other actuators for heating mode. | No | Yes |
| S.104 | Heating mode: Compressor active The compressor works in order to meet the heat demand. | No | Yes |
| S.107 | Heating mode: Pump overrun The heat demand is met, the compressor is switched off. The pump and fan overrun. | No | Yes |
| S.111 | Cooling mode: Compressor switched off The cooling demand is met, the demand is ended by the system control. The compressor is switched off. | No | Yes |
| S.112 | Cooling mode: Compressor blocked The compressor is blocked for cooling mode because the heat pump is outside of its application limits. | Partly | Yes |
| S.113 | Cooling mode: Pump prerun The start conditions for the compressor in cooling mode are checked. Start the other actuators for cooling mode. | No | Yes |
| S.114 | Cooling mode: Compressor active The compressor works in order to meet the cooling demand. | No | Yes |
| S.117 | Cooling mode: Pump overrun The cooling demand is met, the compressor is switched off. The pump and fan overrun. | No | Yes |
| S.125 | Heating mode: Electric back-up heater active The immersion heater is used in heating mode. | No | Yes |
| S.132 | DHW generation: Compressor blocked The compressor is blocked for domestic hot water mode because the heat pump is outside of the application limits. | Partly | Yes |
| S.133 | DHW generation: Pump prerun The start conditions for the compressor in domestic hot water mode are checked. Start the other actuators for domestic hot water mode. | No | Yes |
| S.134 | Domestic hot water mode: Compressor active The compressor works in order to meet the domestic hot water demand. | No | Yes |
| S.135 | Domestic hot water mode: Electr. back-up heater active The immersion heater is used in domestic hot water mode. | No | Yes |
| S.137 | DHW generation: Pump overrun The domestic hot water demand is met, the compressor is switched off. The pump and fan overrun. | No | Yes |
| S.141 | Heating mode: Electr. back-up heater off The heat demand is met, the immersion heater is switched off. | No | Yes |
| S.142 | Heating mode: Electric back-up heater blocked The immersion heater is blocked for heating mode. | Partly | Yes |
| S.151 | DHW mode: Electr. back-up heater switched off The domestic hot water demand is met, the immersion heater is switched off. | No | Yes |
| S.152 | DHW mode: Electr. back-up heater blocked The immersion heater is blocked for domestic hot water mode. | Partly | Yes |
| S.173 | Waiting period: No operation approval from ESCO The mains voltage supply is interrupted by the energy supply company. The maximum anti-cycling time is set in the configuration. | Partly | Yes |
| S.176 | External electrical output limit active The external electrical output limit is active. | Partly | Yes |
| S.202 | Purge programme for building circuit active The purge programme for the building circuit is active. | No | Yes |
| S.203 | Actuator test programme active The test programme for actuating the actuators is active. | No | Yes |
| S.240 | Waiting period: Compressor oil temperature too low The temperature of the compressor oil is too low. The temperature at the compressor inlet or outlet is too low for the compressor start. The oil sump heating is switched on. | Partly | Yes |
| S.255 | Outside of the operating range: Air inlet temperature too high The temperature in the outdoor unit's air inlet is too high. It is outside of the heat pump's operating range. | Partly | Yes |
| S.256 | Outside of the operating range: Air inlet temperature too low The temperature in the outdoor unit's air inlet is too low. It is outside of the heat pump's operating range. | Partly | Yes |
| S.272 | Remaining feed head limit active The remaining feed head that is set under the configuration is reached. | Partly | Yes |
| S.273 | Building circuit flow temperature too low The flow temperature that is measured in the building circuit is below the application limits. | Partly | Yes |
| S.275 | Building circuit volume flow too low Building circuit pump defective. All consumers in the heating system are closed. The values fall below the specific minimum volume flows. Check that the dirt filter is permeable. Check the stopcocks and thermostatic valves. Ensure that the flow rate … | Partly | Yes |
| S.276 | Wait. per.: Underfl. surf.-mnt thermostat blocks the unit Contact S20 is open at the heat pump's main PCB. Incorrect limit thermostat setting. Flow temperature sensor (heat pump, gas-fired boiler, system sensor) measures values that deviate downwards. Adjust the maximum flow temperature for the direct heating … | Partly | Yes |
| S.278 | Outside of the operating range: Building circuit flow temperature too high The building circuit's flow temperature is too high for the heat pump. | Partly | Yes |
| S.285 | Compressor outlet temperature too low The temperature at the compressor outlet is too low. | Partly | Yes |
| S.287 | Outside of the operating range: Fan 1 rotational speed too high Fan 1 is turning too quickly. The cause is likely to be wind affecting the outdoor unit. It is not possible to start or operate the heat pump. | Partly | Yes |
| S.289 | Compressor current limit active The set current limit is active. In the heat pump, based on the customer's home installation, a current limit can be activated and set. The heat pump then limits its intake current to the set value. | Partly | Yes |
| S.290 | Waiting period: Switchon delay active The switch-on delay in the heat pump is active. | Partly | Yes |
| S.303 | Waiting period: Compressor outlet temperature too high The temperature at the compressor outlet is too high. | Partly | Yes |
| S.304 | Waiting period: Evaporation temperature too low The evaporation temperature in the refrigerant circuit is too low. The temperature in the environment circuit (heating/domestic hot water generation) or in the building circuit (cooling) is too low for the compressor to start. | Partly | Yes |
| S.305 | Waiting period: Condensation temperature too low The condensation temperature in the refrigerant circuit is too low. The temperature in the building circuit (heating) or in the environment circuit (cooling) is too low for the compressor to start. | Partly | Yes |
| S.306 | Waiting period: Evaporation temperature too high The evaporation temperature in the refrigerant circuit is too high. The temperature in the environment circuit (heating/domestic hot water generation) or in the building circuit (cooling) is too high for the compressor to start. | Partly | Yes |
| S.308 | Waiting period: Condensation temperature too high The condensation temperature in the refrigerant circuit is too high. The temperature in the building circuit (heating) or in the environment circuit (cooling) is too high for the compressor to start. 8000043014_01 Installation and maintenance instructions 29 | Partly | Yes |
| S.312 | Building circuit return temperature too low Return temperature in the building circuit too low for compressor to start. Heating: Return temperature < 5 °C. Cooling: Return temperature < 10 °C. Cooling: Check that the 4-port diverter valve works correctly. | Partly | Yes |
| S.314 | Building circuit return temperature too high Return temperature in the building circuit too high for the compressor to start. Heating: Return temperature > 56 °C. Cooling: Return temperature > 35 °C. Cooling: Check that the 4-port diverter valve works correctly. Check the sensors. | Partly | Yes |
| S.351 | Outside of the operating range: Electric back-up heater flow temperature too high The flow temperature downstream of the electric back-up heater is too high. The appliance is outside of the operating range. | Partly | Yes |
| S.516 | De-icing active The heat pump de-ices the outdoor unit's heat exchanger. The heating mode is interrupted. The maximum de-icing time is 16 minutes. | No | Yes |