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Heat pump outdoor unit
Heat pump fault codes

NIBE heat pump alarms: alarm codes, causes and parts

All 260 alarm codes for NIBE heat pumps, plus the faults that show no code. Type your code or choose your symptom.

In brief

A fault on a NIBE heat pump usually means that the appliance has locked out or is reporting an alarm code. Note the code on the display and look it up below: for each code you will find its meaning, checks you can safely do yourself and the parts that are often checked or replaced. Frequently searched: 52 (maximum thermostat tripped (element)), 1 (sensor error), 225 (flow/return reversed). No code? Check the power supply, the settings and the filters, and reset once. If the fault comes back, call in a qualified professional.

Most searched NIBE alarms

These are the codes that visitors to this site search for most often.

See the 25 most searched fault codes of 2026, with the figures behind them →

NIBE heat pump faults without a code on the display

Not every fault shows a code. These are the symptoms we come across most often with NIBE appliances, with what you can check yourself before calling someone out.

Heat pump no longer produces heat

Check that the system has enough pressure and whether there is a message on the display or in the app. After a power cut, some units start up in a safe mode and have to be released manually. View the matching parts → Read also: heat pump freezes or defrosts constantly →

Outdoor unit freezes or defrosts constantly

A thin layer of ice in frosty weather is normal; the unit defrosts itself periodically. If the ice stays or the unit defrosts every few minutes, the airflow is obstructed or something is wrong with the defrost control. View the matching parts → Read also: heat pump freezes or defrosts constantly →

Too little or too cold hot water

Check the set hot water temperature and whether the electric immersion heater is enabled. A sharp drop in hot water capacity often points to a faulty cylinder sensor or a worn anode in the tank. View the matching parts → Read also: replace the anode before the tank fails →

Noise or vibrations

A noticeably louder noise than normal usually comes from the fan or from vibrations carried through the pipework. Check that the unit stands clear and that the anti-vibration mounts are intact. View the matching parts → Read also: noise and ice on the outdoor unit →

NIBE heat pump alarm codes 1 to 150 of 260

The code list is split over 2 pages. Looking for a specific code? Use the search at the top of this page: it searches all 260 codes in one go.

CodeCause
1Sensor error BT1 (outdoor sensor): Sensor not connected or defective
100Permanent communication error with inverter: Permanent communication error with inverter
101Sensor error BT1 (outdoor sensor): Sensor not connected or defective
102Sensor error BT2: No sensor value temporarily available
103Sensor error BT3 (heat pump return): Sensor not connected or defective (return sensor)
104Sensor error BT4: No sensor value temporarily available
106Sensor error BT6: No sensor value temporarily available
107Sensor error BT11: Sensor not connected or defective (condenser out)
108Sensor error BT8: No sensor value temporarily available
109Sensor error BT14 (hot gas sensor): Sensor not connected or defective (hot gas sensor)
11Sensor error BT11 (source OUT): Sensor not connected or defective
110Sensor error BT10: No sensor value temporarily available
112Sensor error BT12: No sensor value temporarily available
114Sensor error BT14: No sensor value temporarily available
114Water/water: Sensor error AZ1-BT21 (extract air) | Ventilation air: Sensor error BT21: Sensor not connected or defective (extract air)
116Sensor error BT25: Sensor not connected or defective (flow temperature sensor outside unit)
116Sensor error BT16: No sensor value temporarily available
118Sensor error BT18: No sensor value temporarily available
120Sensor error BT20: No sensor value temporarily available
122Sensor error BT63: Sensor not connected or defective (flow sensor after electric element)
125Sensor error EP30-BT54: Sensor not connected or defective (solar panel sensor)
127Sensor error EQ1-BT64: Sensor not connected or defective (source, flow)
130Permanent communication error emitter system 5 (AXC): Communication error with accessory card. Possible external cause/lack of cable screening
132Permanent communication error emitter system 7 (AXC): Communication error with accessory card. Possible external cause/lack of cable screening
14Sensor error BT14 (hot gas): Sensor not connected or defective (hot gas sensor)
140Compressor phase 1 temporarily not present: Compressor phase 1 temporarily interrupted
142Compressor phase 3 temporarily not present: Compressor phase 3 temporarily interrupted
145Sensor error EQ1-BT57: Sensor not connected or defective (source cooling)
146ERS accessory blocked by the level monitor: Accessory ERS1 blocked by level sensor
147Fault caused by heat pump: Sensor error MHI (evaporator BT16)
148ERS accessory blocked by the level monitor: Accessory ERS3 blocked by level sensor
149ERS accessory blocked by the level monitor: Accessory ERS4 blocked by level sensor
150Fault caused by heat pump: Sensor error MHI (liquid line BT17)
151Sensor error BT51 Pool 40 (swimming pool 1): Sensor not connected/defective POOL40 1
155Hot gas alarm (BT14): The hot gas sensor (BT14) is temporarily above the
158Low defrost temperature: Defrost sensor (BT76) measures below -25 degrees
158Compressor phase 1 not present: Compressor phase missing or <160V for more than 30 min.
160Compressor phase 3 not present: Compressor phase missing or <160V for more than 30 min.
160High outgoing source fluid temperature: Source OUT temperature has reached the set minimum temperature
162High condenser OUT temperature, compressor outside operating range: Condenser OUT has reached the maximum permitted temperature
162Soft starter PCB overheated: Fuses of the soft starter board defective
164Low exhaust air temperature: See alarm 64
165Low pressure alarm (compressor): Low pressure sensor tripped
166Problem with electric anode: Fault detected in the electric anode
168Level switch triggered (source): Level switch tripped
170Hot gas alarm (compressor): Max. hot gas temp. reached, compressor stopped
171Communication error with base PCB (AA2): Communication error with the base board
172Wrong firmware type loaded: Serial number does not match loaded firmware
173Communication error with emitter system 2 (AXC): Communication with accessory card for climate system 2 missing
175Soft starter PCB starting up: The soft starter board is starting up, this takes a maximum of 20 seconds
175Low outgoing source fluid temperature (BT11): The outgoing source fluid is colder than the set protection temperature
177Communication error with shunt-controlled auxiliary heater (AXC): Communication with accessory card for additional shunt-controlled auxiliary heater missing
179Communication error with FLM module: Communication with FLM accessory card missing
181Boiler disinfection failed (legionella prevention): Periodic increase did not reach the set temp. within 5 hours
183Heat pump is defrosting: Defrosting in progress
183Permanent communication error emitter system 2 (AXC): No communication with accessory card
185Permanent communication error emitter system 4 (AXC): No communication with accessory card
185Anti-freeze protection supply air: Supply air (BT22) or discharge air (BT69) is below 5 degrees
187Permanent communication error pool 40 (swimming pool 1, AXC): No communication with accessory card
188Temporary communication error with solar module (AXC): Temporary communication error with SOLAR40 accessory card
190Temporary communication error with external source pump (AXC): Temporary communication error with groundwater pump accessory card
192Temporary communication error with HPAC module: Temporary communication error with 2-pipe cooling accessory card
192Permanent communication error step-controlled auxiliary heater (AXC): No communication with accessory card
194Temporary communication error with HPAC module: Temporary communication error with 4-pipe cooling accessory card
195Permanent communication error groundwater pump: No communication with accessory card
196Temporary communication error with HPAC module: Temporary communication error with room sensor system 1 accessory card
198Temporary communication error with HPAC module: Temporary communication error with room sensor system 3 accessory card
198Permanent communication error 2-pipe cooling (AXC): No communication with accessory card
20Water/water: Sensor error AZ1-BT20 (discharge air) Ventilation air: Sensor error BT20: Sensor not connected or defective (discharge air)
200Communication error with inverter module: Empty
202Inverter error: Inverter gives an alarm
204Inverter fault type II: Permanent inverter error type II
205Permanent communication error with inverter
206Permanent communication error additional DHW (AXC): No communication with accessory card for 15 sec.
207Communication error PCA accessory climate system 6: Communication error with accessory card. Possible external cause/lack of cable screening
208Communication error with Acc-EB1: No communication with accessory card for 15 sec.
209Communication error PCA accessory climate system 8: Communication error with accessory card. Possible external cause/lack of cable screening
213Inverter error type I: Temporary inverter error
214High evaporator inlet temp.: The source inlet temperature has exceeded the set value.
215Inverter error type III: Temporary inverter error type III
218Rotor blocked: Possible power supply problem. Inverter (PCB) defective or poor connection between compressor and inverter.
219Periodic increase failed: The periodic increase did not reach the end temperature within 5 hours
22Sensor error DEW-BT6: Sensor not connected or defective (DHW sensor, additional DHW)
221Low pressure alarm (compressor): Heat pump (indicated unit) sends an error message to the control
223Communication alarm: Heat pump (indicated unit) sends an error message to the control
225Flow/return reversed: Heat pump (indicated unit) sends an error message to the control
228Defrost error: Heat pump (indicated unit) sends an error message to the control
229High pressure alarm (compressor): Heat pump (indicated unit) sends an error message to the control
230Hot gas alarm: Heat pump (indicated unit) sends an error message to the control
231Motor protection alarm: Heat pump (indicated unit) sends an error message to the control
233Fan error: Heat pump (indicated unit) sends an error message to the control
235Sensor error: Heat pump (indicated unit) sends an error message to the control
236Sensor error AZ2-BT20: Sensor not connected/defective (discharge air)
237Short compressor run time: Compressor stopped too early 3 times: compressor run time too short
238Sensor error AZ2-BT26: Sensor not connected/defective (source IN)
239Phase sequence error: Heat pump (indicated unit) sends an error message to the control
240Sensor error AZ3-BT21: Sensor not connected/defective (discharge)
242Sensor error AZ4-BT20: Sensor not connected/defective (discharge)
242Communication error with FLM module: Communication with FLM accessory card missing
243Sensor error AZ4-BT21: Sensor not connected/defective (discharge)
245Communication error FLM 2: No communication with accessory FLM2 temporarily
247Communication error FLM 4: No communication with accessory FLM4 temporarily
249Communication error ACS45: No communication with accessory card temporarily
25Sensor error BT25 (heating flow): Sensor not connected or defective (external return sensor)
250Communication error ACC-SMS 40: No communication with accessory card temporarily
252Communication error with slave: No communication with slave heat pump
252This alarm was generated by the heat pump: Power electronics overheated
254This alarm was generated by the heat pump: Communication between inverter board and control board interrupted
255Motor protection alarm source pump: Source pump motor protection active
256This alarm was generated by the heat pump: Low amount of refrigerant
258This alarm was generated by the heat pump: Overcurrent, inverter A/F module
258Sensor error EQ1-BT57: Sensor not connected/defective (source cooling)
261This alarm was generated by the heat pump: Temperature deviation measured on the heat exchanger sensor (Tho-R1/R2), 5 times within 60 min. or continuously for 60 min.
263Heat pump: Wrong voltage from inverter output: Wrong voltage coming from the inverter
265Heat pump: Continuous power electronics fault for 15 min: Continuous power electronics fault (>15 min)
267Heat pump: inverter start-up fault: Inverter start-up fault
268Low extract air temperature: Discharge air temp. (BT21) in ERS (AZ30) was below 0 degrees within 10 minutes
27Sensor error BP8: Sensor not connected or defective (low pressure sensor)
270Communication error accessory FTX: Communication to accessory card missing, possibly due to an external influence/lack of cable screening
270Compressor preheating active: Empty
272Outdoor air too warm measured EB101 (BT28): EB 101 sends an error message to the control
272Communication error with slave 2: No communication with slave heat pump (EB102) temporarily
274Communication error with slave 4: No communication with slave heat pump (EB104) temporarily
274Compressor phase overloaded: Load monitor limits the compressor output below the required output
276Communication error with source shunt valve: Communication to accessory card missing
276Communication error with slave 6: No communication with slave heat pump (EB106) temporarily
278Communication error with slave 8: No communication with slave heat pump (EB108) temporarily
278Heat pump: Sensor error MHI ambient air: Sensor error MHI ambient air
280Heat pump: Sensor error MHI suction side: Sensor error MHI suction gas
282Communication error ACC.EQ1: 3 consecutive communication errors to ACS 310
288Maximum heat pump flow temperature reached: Outgoing temperature of heat pump has exceeded the max. temp. on BT2 and/or BT63. Possible causes: - Incorrectly connected - Incorrectly adjusted flow - Emitter system or buffer too small - Incorrect heating curve selected
29Sensor error BT29: Sensor not connected or defective (compressor oil temperature)
290Fan alarm: Speed meter (tacho signal) of the fan indicates speed 0
292Sensor error BT74 cooling/heating sensor: Sensor not connected/defective (cooling/heating sensor)
294Heat pump not compatible with indoor unit: The outdoor unit connected to the VVM320 is not an F2030-7, F2030-9, F2040-8, F2040-12. Dip switch settings on PCB not correct
294Anti-freeze protection evaporator (supply air): Supply air
298Incompatible heat pump (SMO20 / SMO40 + S2125): The S2125 software does not work with the SMO40 software.
3Sensor error BT3 (heat pump return): Sensor not connected or defective (condenser IN)
301Communication error with slave 1: No communication with slave heat pump (EB101) temporarily
302Communication error PCA accessory OPT: Can be caused by temporary interference such as thunderstorms. Try to reset the alarm; if the alarm returns, contact your installer
303Communication error with slave 3: No communication with slave heat pump (EB103) temporarily
304Internal error OPT: GBM alarm. This fault is caused by the gas boiler and is reset automatically.
305Communication error with slave 5: No communication with slave heat pump (EB105) temporarily
306Communication error with GP1: No communication with circulation pump in VVM S320
307Communication error with slave 7: No communication with slave heat pump (EB107) temporarily
313Dry running of circulation pump GP1 or source pump GP2: Little to no flow
315Sensor error on EB101: Sensor error detected on EB101 of the COM interface MHI-EMMY
317Sensor error on EB101-BT12: Sensor error detected on EB101 of the COM interface MHI-EMMY
319Inverter alarm Type II: A temporary communication alarm occurred 3 times within 2 hours or has been continuously active for 1 hour
319Communication error EB103/4-GP12 (AXC): Communication with accessory card for GP12s missing

Order parts for your NIBE heat pump

NIBE parts are available from Instalpunt; shipping to EU countries from €17.95 (€24.95 for more distant countries), usually 3–5 working days.

View NIBE parts →

Frequently asked questions about NIBE alarms

What does a fault on a NIBE heat pump mean?

The appliance is reporting that it has shut itself down or cannot continue. The code on the display points to the group of causes: ignition, water pressure, a sensor, the fan or communication with the thermostat. The table above shows, for each code, what NIBE means by it.

How do I reset my NIBE heat pump?

The reset button is on the control panel of your NIBE heat pump; on most appliances you hold it down for two to five seconds until the display responds. Reset once. If the same fault comes straight back, resetting will not solve it and a part or a setting needs attention. Always consult the manual for your model: the position of the button and how long to press it differ per series.

Can I fix a NIBE fault myself?

You can top up the water pressure, bleed the system, replace filters and clean a siphon yourself. Anything behind the sealed section of a gas appliance is a different matter: work on the gas valve, burner, heat exchanger and flue must be carried out by a certified gas engineer.

How much does it cost to fix a fault?

That depends on the cause and whether a part is needed. With us you can see the part straight away with its price and delivery time, so you know where you stand in advance. If you call in an engineer, always ask about the call-out charge and hourly rate before they come.

Where can I find the right part for my NIBE?

Check the rating plate for the exact type and use it to search our catalogue, or search directly by the manufacturer number of the faulty part. Each part lists the appliances it fits.

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