Function of digital input/output (IO1 and IO2 ports)
The device has one multifunctional analog/digital input/output (between ports IO1 and IO2). Below, there's a summary of the available options for the functionality of the input.
SET/GET IO1/IO2 function:
The logic for all 3 options have their reversed counterpart in terms of the input to IO1 and IO2. E.g. 00 and 01 are the same, but the closed/opened logic is reversed. The logic is the same for 02-03 and 04-05.
Occupancy sensor
Option 1: Set-point decrease
00: open → occupied, closed → unoccupied (set-point decrease) (default)
It means that if the OCC port is opened, then the room is considered occupied. And if the OCC port is closed, then the room is considered unoccupied, temperature set-point and fan speed are decreased as described here.
01: closed → occupied, open → unoccupied (set-point decrease)
Same basic logic as in 00, but reversed open/close status.
You can read the occupancy sensor status with the command:
When the occupancy sensor status changes, the command is sent together with the keepalive of the device. The keepalive data in the example below is omitted for clarity.
Byte index
Hex value – Meaning
0
70 – The command code.
1
Occupancy sensor:
00: occupied;
01: unoccupied (set-point decrease).
Example downlink: 0x7001 – The status is unoccupied.
Option 2: Fan off, valve closed
02: open → occupied, closed → unoccupied (fan off, valve closed)
Similar to 00 and 01, but set-point remains the same as the user has set and the FAN and valve are turned off.
03: close → occupied, open → unoccupied (fan off, valve closed)
Same logic as 02, but reversed open/close status.
You can read the occupancy sensor status with the command:
When the occupancy sensor status changes, the command is sent together with the keepalive of the device. The keepalive data in the example below is omitted for clarity.
Byte index
Hex value – Meaning
0
71 – The command code.
1
Occupancy sensor:
00: occupied;
01: unoccupied (fan off, valve closed).
Example downlink: 0x7101 – The status is unoccupied.
Dew point reached/not reached
04: closed → dew point reached, open → dew point not reached
In case you have a dew-point sensor already installed in your FCU, then in this mode, the FCT can change the overall operation based on the sensor. If the OCC port is closed, then:
Dew-point alarm icon appears on the display
Dew-point alarm is sent in the keep-alive
General operation of the FCT is disabled, valve is closed, FAN is turned OFF
All keys are disabled before the OCC port is open again.
05: open → dew point reached, closed → dew point not reached
Same logic as 04, but reversed open/close status.
You can read the dew point sensor status with the command:
When the dew point sensor status changes, the command is sent together with the keepalive of the device. The keepalive data in the example below is omitted for clarity.
Byte index
Hex value – Meaning
0
72 – The command code.
1
Dew point sensor:
00: dew point not reached;
01: dew point reached.
Example downlink: 0x7201 – The dew point has been reached.
Filter alarm
06: closed → filter alarm
When the OCC is closed, then the device:
Shows an icon on the display for the filter
Continues normal operation
07: open → filter alarm
Same logic as 06, but reversed open/close status
You can read the filter alarm status with the command:
When the filter alarm status changes, the command is sent together with the keepalive of the device. The keepalive data in the example below is omitted for clarity.
Byte index
Hex value – Meaning
0
73 – The command code.
1
Filter alarm:
00: The filter alarm is off;
01: The filter alarm is on;
Example downlink: 0x7301 – The filter alarm is on.
Defined by the application or automatic changeover:
In case you use an application (wiring diagram) with ECM fan OR you've decided to use the OCC for automatic change-over, then the OCC enters the following modes.
In those modes, you cannot change the function of the OCC unless you change the application or disable the automatic change-over
08: 10k NTC for auto changeover
Used in case you want to use the auto changeover functionality. Read more about the settings of the automatic changeover here.
When an error occurs in the external (10K NTC) temperature sensor, 7D command is sent together with the keepalive of the device. An error message is displayed on the device screen. The auto changeover function is disabled, and the device remains in the last mode.
Аvailable only for devices with firmware version ≥ 1.9.
If the external (10k NTC) temperature sensor circuit is open or shorted during a read operation with command 74, the device returns 0xFF.
Аvailable only for devices with firmware version ≥ 2.1
You can read the mode changed by the changeover function end external NTC sensor temperature with the command:
Byte index
Hex value – Meaning
0
74 – The command code.
1
XX - External NTC temperature (1°C resolution).
2
Automatic changeover:
00: the changeover setpoint threshold is not reached;
01: heating mode;
02: cooling mode.
Example downlink: 0x742E01
2E convert to decimal 46 => External NTC temperature = 46°C.
01 – Heating mode.
09: ECM Fan
In case your system has an ECM Fan, then the OCC port is used to control the fan and cannot be used for any other purpose. View available wiring diagrams (applications) here.
0А: 10k NTC control sensor instead of the internal temperature sensor
Enables the use of an external 10k NTC control sensor, located at a distance from the device. The supported temperature measurement range is 0 to 99°C, allowing the device to be used for applications such as boiler temperature control."
When an error occurs in the external (10K NTC) temperature sensor, 7D command is sent together with the keepalive of the device. An error message is displayed on the device screen, and a temperature value of -40°C is shown. The device operation is halted — all outputs are turned off — and the keepalive reports a temperature of -40°C."
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