Nilan CTS602

Name: Nilan CTS602
Brand: Nilan
SKU: f3b950d8-ea22-4468-9832-c5e68f88352b

Controller for Nilan ventilation units with heat pump, hot water and central heating.

The Nilan CTS602 is the controller in Nilan ventilation units with heat recovery that can also run a heat pump, a hot water tank and central heating. This Modbus RTU template reads all temperatures, humidity, CO2, fan steps, operating state and alarms, and lets you switch the unit, change mode, ventilation step and setpoints from ModbusCloud.

Protocol: Modbus RTU
Connection: RS485, 19200 baud
Registers: 314, read and write

Brand: Nilan
Key readings: Outdoor and supply temperatures · Room and exhaust temperature · Hot water temperatures · Humidity and CO2 · Fan steps and speeds · Operating mode and state · Active alarms · Days to filter change
Available commands: On and off · Operating mode · Ventilation step · Room temperature setpoint · Hot water setpoints · Alarm reset
Compatible models: CTS602 · CTS602 with HMI350T panel
Last updated: 12 October 2026

Registers (314)

314 read, 151 write

Name	Unit	Access
Protocol Version		Read
Software Version Major		Read
Software Version Minor		Read
Software Version Release		Read
Application Id		Read
Hardware Type		Read
User Function Input		Read
Air Filter Alarm Input		Read
Door Contact Input		Read
Smoke Alarm Input		Read
Motor Thermo Fuse Input		Read
Heating Surface Frost Overheat Input		Read
Airflow Monitor Input		Read
High Pressure Switch Input		Read
Low Pressure Switch Input		Read
Hot Water Boiling Input		Read
Hot Water 3-Way Valve Position Input		Read
Hotgas Defrost Type Input		Read
Defrost Thermostat Input		Read
User Function 2 Input		Read
Air Damper Closed Input		Read
Air Damper Opened Input		Read
FC And Thermo Alarm Input		Read
Brine Pressostat Input		Read
T0 Controller Temperature	°C	Read
T1 Fresh Air Intake Temperature	°C	Read
T2 Inlet Temperature Before Heater	°C	Read
T3 Room Exhaust Temperature	°C	Read
T4 Outlet Temperature	°C	Read
T5 Condenser Temperature	°C	Read
T6 Evaporator Temperature	°C	Read
T7 Inlet Temperature After Heater	°C	Read
T8 Outdoor Temperature	°C	Read
T9 Heating Surface Temperature	°C	Read
T10 External Room Temperature	°C	Read
T11 Hot Water Top Temperature	°C	Read
T12 Hot Water Bottom Temperature	°C	Read
T13 Central Heating Return Temperature	°C	Read
T14 Central Heating Supply Temperature	°C	Read
T15 User Panel Room Temperature	°C	Read
T16 AUX Temperature	°C	Read
T17 Preheater Intake Temperature	°C	Read
T18 Pressure Pipe Temperature	°C	Read
Suction Pressure	bar	Read
Discharge Pressure	bar	Read
Humidity	%RH	Read
CO2	ppm	Read
Alarm Status		Read
Alarm 1 Code		Read
Alarm 1 Date		Read
Alarm 1 Time		Read
Alarm 2 Code		Read
Alarm 2 Date		Read
Alarm 2 Time		Read
Alarm 3 Code		Read
Alarm 3 Date		Read
Alarm 3 Time		Read
Actual On Off State		Read
Actual Operation Mode		Read
Actual Control State		Read
Time In State	s	Read
Ventilation Step Setpoint		Read
Inlet Fan Step		Read
Exhaust Fan Step		Read
Days Since Filter Alarm	d	Read
Days To Filter Alarm	d	Read
Summer State		Read
Inlet Temperature Request	°C	Read
Controlled Temperature	°C	Read
Room Temperature	°C	Read
Heat Exchanger Efficiency	%	Read
Requested Capacity	%	Read
Actual Capacity	%	Read
Compressor Type		Read
Hot Water Type		Read
Hot Water Anode State		Read
External Heating Setpoint	°C	Read
Preheater Block Remaining	s	Read
DPT In Session		Read
DPT Air Flow 1	m³/h	Read
DPT Air Flow 2	m³/h	Read
DPT Pressure 1	Pa	Read
DPT Pressure 2	Pa	Read
DPT2 In Session		Read
DPT2 Air Flow 1	m³/h	Read
DPT2 Air Flow 2	m³/h	Read
DPT2 Pressure 1	Pa	Read
DPT2 Pressure 2	Pa	Read
Bypass Damper		Read
After Heating Element	%	Read
Heat Exchanger De-icing		Read
CO2 Sensor Present		Read
Stop At Low Room Temperature		Read
Last Damper Self-Test		Read
Days Since Filter Change	d	Read
Low Fan Speed At Low Outdoor Temperature		Read
Room Temperature Setpoint	°C	Read
Control Sensor Temperature	°C	Read
Event Log Alarm Code		Read
Event Log Date		Read
Event Log Time		Read
Event Log T1 Temperature	°C	Read
Event Log T3 Temperature	°C	Read
Event Log T4 Temperature	°C	Read
Event Log T5 Temperature	°C	Read
Event Log T6 Temperature	°C	Read
Event Log T7 Temperature	°C	Read
Event Log T8 Temperature	°C	Read
Event Log T9 Temperature	°C	Read
Event Log T10 Temperature	°C	Read
Event Log T11 Temperature	°C	Read
Event Log T12 Temperature	°C	Read
Event Log T13 Temperature	°C	Read
Event Log T14 Temperature	°C	Read
Event Log T15 Temperature	°C	Read
Event Log Digital Inputs 1-8		Read
Event Log Digital Inputs 9-16		Read
Event Log Digital Outputs 1-8		Read
Event Log Digital Outputs 9-16		Read
Event Log Analog Output 1	%	Read
Event Log Analog Output 2	%	Read
Event Log Analog Output 3	%	Read
Event Log Analog Output 4	%	Read
Event Log Control State		Read
Humidity Average	%RH	Read
Expansion Board Id		Read
Ventilation State		Read
Node Address		Read and write
Air Flap Output		Read
Smoke Flap Output		Read
Bypass Flap Open Output		Read
Bypass Flap Close Output		Read
Air Heat Circulation Pump Output		Read
Air Heating Selected Output		Read
Air Heater Relay 1		Read
Air Heater Relay 2		Read
Air Heater Relay 3		Read
Compressor Output		Read
Compressor 2 Output		Read
4-Way Valve Output		Read
Hotgas Valve Heat Output		Read
Hotgas Valve Cool Output		Read
Air Condenser Active Output		Read
Air Condenser Inactive Output		Read
Hot Water Heater Output		Read
Hot Water 3-Way Valve Output		Read
Central Heating Circulation Pump Output		Read
Central Heating Relay 1		Read
Central Heating Relay 2		Read
Central Heating Relay 3		Read
External Radiator Heat Output		Read
User Function Active Output		Read
User Function 2 Active Output		Read
Defrost Active Output		Read
Alarm Relay Output		Read
Preheater Output		Read
EHD Or BAH Output		Read
Exhaust Fan Speed	%	Read
Inlet Fan Speed	%	Read
Air Heater Capacity	%	Read
Central Heater Capacity	%	Read
Compressor Capacity	%	Read
Preheater Capacity	%	Read
Rotary Heat Exchanger	%	Read
Clock Second		Read and write
Clock Minute		Read and write
Clock Hour		Read and write
Clock Day		Read and write
Clock Month		Read and write
Clock Year		Read and write
Alarm Reset		Read and write
Week Program Select		Read and write
User Function Active		Read and write
User Function Select		Read and write
User Function Period	min	Read and write
User Function Ventilation Step		Read and write
User Function Temperature	°C	Read and write
User Function Temperature Offset	°C	Read and write
User Function 2 Active		Read and write
User Function 2 Select		Read and write
User Function 2 Period	min	Read and write
User Function 2 Ventilation Step		Read and write
User Function 2 Temperature	°C	Read and write
User Function 2 Temperature Offset	°C	Read and write
Data Log Interval	min	Read and write
Machine Type		Read and write
On Off Select		Read and write
Operation Mode Select		Read and write
Ventilation Step Select		Read and write
User Temperature Setpoint	°C	Read and write
Service Mode Select		Read and write
Service Mode Capacity	%	Read and write
Preset Request		Read and write
Air Exchange Mode		Read and write
Cooling High Ventilation Step		Read and write
Damper Test Day		Read and write
Last Damper Test Date		Read and write
Damper Test State		Read and write
Filter Alarm Type		Read and write
Cooling Setpoint Select		Read and write
Inlet Temperature Min Summer	°C	Read and write
Inlet Temperature Min Winter	°C	Read and write
Inlet Temperature Max Summer	°C	Read and write
Inlet Temperature Max Winter	°C	Read and write
Summer Winter Limit	°C	Read and write
Night Cooling Day Temperature	°C	Read and write
Night Cooling Room Setpoint	°C	Read and write
Control Sensor Select		Read and write
Heat Source Select		Read and write
Condenser Low Temperature Curve	°C	Read and write
Condenser High Temperature Curve	°C	Read and write
Compressor Start Low Temperature	°C	Read and write
Compressor Stop Time		Read and write
Hot Water Top Setpoint	°C	Read and write
Hot Water Bottom Setpoint	°C	Read and write
Hot Water Priority		Read and write
Scald Protection Temperature	°C	Read and write
Hot Water Electric Supplement		Read and write
Legionella Day		Read and write
Hot Water Bypass Offset	°C	Read and write
External Heating Offset	°C	Read and write
Central Heating Select		Read and write
Central Heating Supply Min	°C	Read and write
Central Heating Supply Max	°C	Read and write
Outdoor Temperature Compensation	°C	Read and write
Heating Curve Select		Read and write
Circulation Pump Mode		Read and write
Central Heating Type		Read and write
PID Regulation Time	s	Read and write
Humidity Low Winter Step		Read and write
Humidity High Step		Read and write
Humidity Limit Low Ventilation	%RH	Read and write
Humidity High Ventilation Timeout	min	Read and write
CO2 High Step		Read and write
CO2 Limit Normal Ventilation	ppm	Read and write
CO2 Limit High Ventilation	ppm	Read and write
User Menu Open		Read and write
Panel Language		Read and write
Preheater Block		Read and write
DPT Calibrate		Read and write
DPT2 Calibrate		Read and write
Fan Pressure Relation	%	Read and write
Supply Air P Control		Read and write
Supply Air I Control	s	Read and write
Extract Air P Control		Read and write
Extract Air I Control	s	Read and write
Step 1 Supply Air Flow	m³/h	Read and write
Step 2 Supply Air Flow	m³/h	Read and write
Step 3 Supply Air Flow	m³/h	Read and write
Step 4 Supply Air Flow	m³/h	Read and write
Step 1 Extract Air Flow	m³/h	Read and write
Step 2 Extract Air Flow	m³/h	Read and write
Step 3 Extract Air Flow	m³/h	Read and write
Step 4 Extract Air Flow	m³/h	Read and write
Step 1 Supply Air Pressure	Pa	Read and write
Step 2 Supply Air Pressure	Pa	Read and write
Step 3 Supply Air Pressure	Pa	Read and write
Step 4 Supply Air Pressure	Pa	Read and write
Step 1 Extract Air Pressure	Pa	Read and write
Step 2 Extract Air Pressure	Pa	Read and write
Step 3 Extract Air Pressure	Pa	Read and write
Step 4 Extract Air Pressure	Pa	Read and write
Room Heating Deadband	°C	Read and write
High Fan Speed At High Indoor Temperature		Read and write
Low Outdoor Temperature Limit	°C	Read and write
Fan Speed At Low Outdoor Temperature		Read and write
Automatic Test Day		Read and write
After Heating Type		Read and write
After Heat Delay	min	Read and write
Summer Min Supply Temperature	°C	Read and write
Summer Max Supply Temperature	°C	Read and write
Winter Min Supply Temperature	°C	Read and write
Winter Max Supply Temperature	°C	Read and write
Room Temperature Deadband	°C	Read and write
Low Room Temperature Ventilation Reduce	°C	Read and write
After Heating Activation		Read and write
Min Inlet		Read and write
Min Exhaust		Read and write
Max Exhaust		Read and write
Fan Start Delay		Read and write
Damper Walking Time	s	Read and write
Defrost Ventilation Level		Read and write
Defrost Bypass Position		Read and write
Defrost Block Time	min	Read and write
Defrost Start Temperature	°C	Read and write
Defrost Stop Temperature	°C	Read and write
Defrost Max Duration Compressor	min	Read and write
Defrost Max Duration Exchanger	min	Read and write
T6 Min Defrost Time	s	Read and write
Week Program Edit Index		Read and write
Week Program Edit Period		Read and write
Week Program Edit Period Next		Read and write
Week Program Edit Function		Read and write
Week Program Edit Start Time		Read and write
Week Program Edit Fan		Read and write
Week Program Edit Temperature	°C	Read and write
Fire Alarm Restart Mode		Read and write
Power Save		Read and write
Alarm Log Index		Read and write
Inlet Fan Scaling	%	Read and write
Exhaust Fan Scaling	%	Read and write
Inlet Step 1 Speed		Read and write
Inlet Step 2 Speed		Read and write
Inlet Step 3 Speed		Read and write
Inlet Step 4 Speed		Read and write
Exhaust Step 1 Speed		Read and write
Exhaust Step 2 Speed		Read and write
Exhaust Step 3 Speed		Read and write
Exhaust Step 4 Speed		Read and write
Air Quality Control Type		Read and write
Heater Output Signal Type		Read and write
Room Controller Response		Read and write
Preheater Defrost Select		Read and write
Preheater Defrost Setpoint		Read and write

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Use cases

Show outdoor, supply, exhaust and hot water temperatures of a Nilan unit on one ModbusCloud dashboard.
Send an email when Alarm Status reports an active alarm or Days To Filter Alarm drops below 7.
Compare heat exchanger efficiency and compressor capacity over the year in the 365 day history.
Raise the ventilation step remotely when a resident reports high humidity in the bathroom.
Lower the hot water setpoint or switch the unit to cooling for the summer from ModbusCloud.

Installation

Switch off the unit and connect RS485 to connector CN7 on the CTS602: pin 2 to A, pin 3 to B and pin 6 to GND.
Wire the other end to the RS485 port of the ModbusCloud Gateway and place a 120 ohm resistor at both ends of the bus.
Check the node address on the panel (default 30); baud rate 19200 and even parity are fixed.
In ModbusCloud, add a Modbus RTU device with address 30, 19200 baud, 8 data bits, even parity and 1 stop bit, and import this template.
Check that T8 Outdoor Temperature and Actual Operation Mode show plausible values.

Things to watch for

The CTS602 does not answer. What should I check?

Check that ModbusCloud uses 19200 baud, even parity and 1 stop bit; the controller cannot be set to anything else. Check the node address (default 30), swap A and B if needed and connect pin 6 GND, because the CTS602 has no opto-isolation and needs a common ground.

Why does a temperature show 2150 instead of 21.5 °C?

The temperatures are sent in hundredths of a degree. The template already divides them by 100; if you added a register by hand, set the scale to 0.01. Temperatures below zero are signed values.

Why can I not write the ventilation step or setpoint?

The CTS602 only accepts writes with function 16, which the template already uses. Writing from ModbusCloud is off per gateway by default and is switched on by request on the control tab. Some settings only work on units with the matching option, such as hot water or central heating.

How do I read older entries of the alarm log?

Write the entry number to Alarm Log Index, then read the Event Log registers for code, date, time, temperatures and outputs of that entry. Date and time are packed in DOS format, so the value needs to be split into year, month, day and time.

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