CTC · A niche brand in the UK. 100 codes across 1 product family, each taken from the manufacturer’s manuals. CTC 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.
100 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| E001 | Risk of freezing: water leaving the heat pump (HP out) too low for defrosting; system water volume or flow may be too low (EcoAir; older numbering used in EcoLogic/EcoPart i600M/i555 manuals). | Partly | Yes |
| E002 | Sensor alarm - external boiler sensor (B9): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E003 | Sensor alarm - brine in sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E005 | Sensor alarm - brine out sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E007 | Sensor alarm - buffer tank sensor (B6): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E010 | Compressor type?: no information about the compressor type is available. | Partly | Yes |
| E012 | Sensor alarm - DHW tank sensor (B5): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E013 | EVO off: fault with the electronic expansion valve control. | Partly | Yes |
| E015 | Sensor alarm - external boiler out sensor (B10): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E016 | Sensor alarm - solar collector in sensor (B30): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E017 | Sensor alarm - solar collector out sensor (B31): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E018 | Sensor alarm - external DHW tank sensor (B43): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E019 | Sensor alarm - pool sensor (B50): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E020 | Sensor alarm - boiler sensor (B8): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E021 | Comm. err. motor protection: HP control card (A5) cannot communicate with the motor protection (A4) (EcoZenith i255/EcoHeat 400 numbering). | Partly | Yes |
| E024 | Fuse blown: fuse F1/F2 has blown. | Partly | Yes |
| E026 | Heat pump: the connected heat pump is in alarm mode. | Partly | Yes |
| E027 | Comm. error HP: display card (A1) cannot communicate with the HP control card (A5). | Partly | Yes |
| E028 | Sensor alarm - heat pump in (HP in) sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E029 | Sensor alarm - heat pump out (HP out) sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E030 | Sensor alarm - outdoor sensor (B15): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E031 | Sensor alarm - primary flow sensor 1 (B1): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E032 | Sensor alarm - primary flow sensor 2 (B2): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E033 | Sensor alarm - primary flow sensor 3 (B3): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E034 | Sensor alarm - primary flow sensor 4 (B4): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E035 | High pressure switch: the refrigerant high-pressure switch has tripped. | Partly | Yes |
| E036 | Sensor alarm - high pressure sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E037 | Sensor alarm - discharge gas sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E040 | Low brine flow: often air in the collector, especially just after installation, or over-long collectors; check brine pump speed and brine filter. | Partly | Yes |
| E041 | Low brine temp: incoming brine temperature from borehole/ground loop too low; cold side dimensioning should be checked. | Partly | Yes |
| E043 | Sensor alarm - low pressure sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E044 | Stop, high compr temp: compressor temperature is high. | Partly | Yes |
| E045 | Stop, low evaporation: evaporation temperature is low. | Partly | Yes |
| E046 | Stop, high evaporation: evaporation temperature is high. | Partly | Yes |
| E047 | Stop, low suction gas (exp. valve): suction gas temperature is low. | Partly | Yes |
| E048 | Stop, low evaporation (exp. valve): expansion valve evaporation temperature is low. | Partly | Yes |
| E049 | Stop, high evaporation (exp. valve): expansion valve evaporation temperature is high. | Partly | Yes |
| E050 | Stop, low superheating (exp. valve): expansion valve superheat is low. | Partly | Yes |
| E052 | Phase 1 missing: phase failure detected. | Yes | Yes |
| E053 | Phase 2 missing: phase failure detected. | Yes | Yes |
| E054 | Phase 3 missing: phase failure detected. | Yes | Yes |
| E055 | Incorrect/wrong phase sequence: compressor would rotate the wrong way; two phases must be swapped with the supply isolated. Generally occurs only at installation. | Yes | Yes |
| E056 | Comm. error motor protection: HP control board (A5) cannot communicate with the motor protection (A4) (EcoLogic, EcoPart i600M, GS/GSi 600, i360, i555 numbering). | Partly | Yes |
| E057 | Motor protect high curr.: high current into the compressor detected. | Partly | Yes |
| E058 | Motor protect low curr.: low current into the compressor detected. | Partly | Yes |
| E061 | Max thermostat: the product has become too hot and the overheat (max) thermostat F10 has tripped; may also trip if stored in extreme cold before installation. | Partly | Yes |
| E063 | Comm. err. relay board: display card (A1) cannot communicate with the relay board (A2). | Partly | Yes |
| E064 | Sensor alarm - return sensor (B7): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E074 | Sensor alarm - room sensor 1 (B11): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E075 | Sensor alarm - room sensor 2 (B12): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E076 | Sensor alarm - room sensor 3 (B13): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E077 | Sensor alarm - room sensor 4 (B14): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E079 | Sensor alarm - solar collector sensor (B33): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E080 | Sensor alarm - suction gas sensor: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E086 | Comm. err. expansion card: display card (A1) cannot communicate with the CTC Solar control/expansion card (A3). | Partly | Yes |
| E087 | Driver: inverter driver fault. | Yes | Yes |
| E088-E109 | Driver: 1 to Driver: 29 - numbered inverter driver fault codes; tell the installer the number shown. | Yes | Yes |
| E117 | Driver: Offline - communication error, heat pump (junction box) and driver not communicating. | Yes | Yes |
| E120 | Sensor alarm - external boiler sensor (B17): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E135 | Risk of freezing (critical): HP out below 15 C during defrost, or more than 15 C difference between HP in and HP out for >20 s. Acknowledge with code 4005 (max three times). | Partly | Yes |
| E137 | Sensor alarm - differential thermostat sensor (B46): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E138 | Sensor alarm - EcoTank lower sensor (B42) / external buffer tank lower: sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E139 | Sensor alarm - EcoTank upper sensor (B41): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E140 | Sensor alarm - EHS tank sensor (B47): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E141 | Sensor alarm - external buffer tank upper sensor (B41): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E142 | Sensor alarm - external buffer tank lower sensor (B42): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E143 | Sensor alarm - external DHW tank sensor (B43): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E152 | 4-way valve: fault with the EcoAir 4-way valve or EcoAir connection pipes connected wrongly; check the charge pump pumps to the heat pump lower connection. | Partly | Yes |
| E160 | Sensor alarm - suction gas sensor (second input, EcoLogic/EcoPart i600M): sensor not connected, short-circuited or value outside the sensor range. If the sensor is important to operation the compressor stops. | Partly | Yes |
| E163 | Defrost max time duration: defrost did not complete within the maximum time; make sure evaporator ice has gone. | Partly | Yes |
| E211 | Risk of freezing low flow (critical): flow < 10 l/min (610M/614M/708M/712M) or < 15 l/min (622M/720M) for >30 s during defrost; EcoAir 600M/700M/C100 with flow sensor. | Partly | Yes |
| E216 | HP flow temp diff (critical): HP in/HP out difference >12 C in heating for >15 minutes (EcoAir 500/600M/700M/C100). | Partly | Yes |
| E217 | HP Charge pump flow (critical): charge pump speed above 70% in heating for more than 15 min (i255) / 30 min (EcoLogic II) (EcoAir 400). | Partly | Yes |
| E218 | Blocking alarm after the fourth [E135] Risk of freezing within a year - heat pump blocked, contact installer. | Yes | Yes |
| E219 | Blocking alarm after the fourth [E211] Risk of freezing low flow - heat pump blocked, contact installer. | Yes | Yes |
| E220 | Blocking alarm after the fourth [E216] HP flow temp diff - heat pump blocked, contact installer. | Yes | Yes |
| E221 | Blocking alarm after the fourth [E217] HP Charge pump flow - heat pump blocked, contact installer. | Yes | Yes |
| I002 | HC1 Heating off - heating circuit 1 in summer mode (DHW only). | No | Yes |
| I005 | HC2 Heating off - heating circuit 2 in summer mode. | No | Yes |
| I006 | HC3 Heating off. | No | Yes |
| I007 | HC4 Heating off. | No | Yes |
| I008 | Tariff HP off - tariff control has switched off the heat pump. | Partly | Yes |
| I009 | Compressor blocked - compressor set to off (e.g. before collector is drilled/dug); factory state; changed in installer settings. | Partly | Yes |
| I010 | Tariff EL off - tariff control has switched off the immersion heater. | No | Yes |
| I011 | Round (ripple) circulation active - supplier load control blocks compressor and electric output. | Partly | Yes |
| I012 | High current, reduced electric output - main fuses at risk of overload; or 2 h max 6 kW limit after power-up. | No | Yes |
| I013 | Start delay - compressor restart delay, usually at least 10 minutes. | Partly | Yes |
| I014 | Drying period active - floor drying function active, days remaining shown. | No | Yes |
| I017 | SmartGrid: Blocking. | No | Yes |
| I018 | SmartGrid: Overcapacity. | No | Yes |
| I019 | SmartGrid: Low price. | No | Yes |
| I021 | Ext. Ctrl Heating 1 - remote control input sets heating circuit 1 on/off. | No | Yes |
| I022 | Ext. Ctrl Heating 2. | No | Yes |
| I023 | Ext. Ctrl Heating 3. | No | Yes |
| I024 | Ext. Ctrl Heating 4. | No | Yes |
| I028 | Holiday period - lowered room temperature and no hot water production. | No | Yes |
| I029 | Bleeding DHW in progress - hot water not at continuous temperature until complete (EcoZenith i360). | No | Yes |
| I030 | Driver block under voltage - heat pump stopped due to insufficient mains voltage; will attempt restart. | Partly | Yes |
| I031 | Driver block alarm - heat pump stopped due to driver failure (e.g. voltage or excessive temperature); will attempt restart. | Partly | Yes |
| I050 | Power limitation activated. | No | Yes |