Belimo · HVAC controller
Air/water actuators ..M(C)24A-MOD, ..R24A-MOD, ..V(K)24A-MOD, ..F24A-MOD, ..RF24A-MOD, ..H24A-MOD Modbus register map
Default configuration
- Protocol
- RS485
- Port
- 502
- Unit ID
- 1
- Addressing
- 0-based
- Byte order
- Big endian
- Word order
- Low word first
- Baud rate
- 38400
- Parity
- None
- Data bits
- 8
- Stop bits
- 2
This device has an RS-485 interface. Reach it through a Modbus RTU-to-TCP gateway, configured with the factory serial settings above.
Register map
| Address | Count | Name | Type | Unit | Scale | Access |
|---|---|---|---|---|---|---|
| 0 | 1 | Setpoint Setpoint for the actuator, scaled between Min (register 105) and Max (register 106). Range 0...10000. Default 0. | UInt16 | % | 0.01 | RW |
| 1 | 1 | Override control 0 = none (default), 1 = open, 2 = close, 3 = min, 4 = mid, 5 = max, 6 = fast open, 7 = fast close. Overrides the setpoint with the defined value. | UInt16 | - | 1 | RW |
| 2 | 1 | Command 0 = none (default), 1 = adaption, 2 = test, 3 = sync, 4 = reset. After the command is sent the register returns to none; reset clears the malfunction and service information in register 104. | UInt16 | - | 1 | RW |
| 3 | 1 | Actuator type 0 = actuator not connected, 1 = air / water, 2 = VAV / EPIV, 3 = fire, 4 = energy valve, 5 = 6-way EPIV. | UInt16 | - | 1 | R |
| 4 | 1 | Relative position Range 0...10000. | UInt16 | % | 0.01 | R |
| 5 | 1 | Absolute position Degrees for actuators with rotary movement, millimetres for actuators with linear movement. | UInt16 | ° | 1 | R |
| 8 | 1 | Sensor 1 value Millivolts when sensor type 1 (register 107) is active, ohms for passive_1K / passive_20K, 0 / 1 for a switch, degrees Celsius or Fahrenheit x10 for the PT1000 / NI1000 / NTC10K2 types. Range 0...65535. | UInt16 | mV | 1 | R |
| 12 | 1 | Analog setpoint Setpoint in percent when the actuator is controlled by the analog signal. | UInt16 | % | 0.01 | R |
| 99 | 1 | Bus termination 0 = inactive (default), 1 = active: the 120 ohm bus termination is enabled. | UInt16 | - | 1 | R |
| 100 | 1 | Series number, 1st part Parts 1, 2 and 4 of the four-part series number are readable; the example 00839-31324-064-008 is read as 00839 / 31324 / 008. | UInt16 | - | 1 | R |
| 101 | 1 | Series number, 2nd part | UInt16 | - | 1 | R |
| 102 | 1 | Series number, 4th part | UInt16 | - | 1 | R |
| 103 | 1 | Firmware version Communication module firmware, e.g. 302 for version 3.02. | UInt16 | - | 1 | R |
| 104 | 1 | Malfunction and service information Bit-coded. Bit 1 mechanical travel increased, bit 2 actuator cannot move, bit 8 internal activity, bit 9 gear train disengaged (manual override pressed), bit 10 bus watchdog triggered. | Binary | - | 1 | R |
| 105 | 1 | Min Lower position limit, range 0...Max-20 percent. Default 0. | UInt16 | % | 0.01 | RW |
| 106 | 1 | Max Upper position limit, range Min+20...100 percent. Default 10000 (100 percent). | UInt16 | % | 0.01 | RW |
| 107 | 1 | Sensor 1 type 0 = none (default), 1 = active / hybrid, 2 = passive_1K, 3 = passive_20K, 4 = switch, 5 = PT1000_C, 6 = NI1000_C, 7 = NTC10K2_C, 8 = PT1000_F, 9 = NI1000_F, 10 = NTC10K2_F. Restart the actuator after a change for correct sensor values. | UInt16 | - | 1 | RW |
| 108 | 1 | Bus fail position 0 = none / last setpoint (default), 1 = fast close, 2 = fast open, 3 = mid position. Becomes active when the bus watchdog (register 109) expires. | UInt16 | - | 1 | RW |
| 109 | 1 | Timeout for bus watchdog 0 = deactivated (default), range 0...3600 s. When a bus fail position is configured the document states a default of 120 s. | UInt16 | s | 1 | RW |
| 118 | 1 | Setpoint source 0 = analog signal on wire 3, 1 = bus (default, setpoint from register 0). | UInt16 | - | 1 | RW |
| 189 | 1 | Fail-safe bridging time 0...10 s. Time the actuator stays in its position after a power failure before moving to the fail-safe position. Only for electronic fail-safe actuators. | UInt16 | s | 1 | RW |
| 190 | 1 | Fail-safe position Position the actuator moves to after a power failure, respecting the bridging time. Range 0...10000. Only for electronic fail-safe actuators; the rotary knob must be in the tool position. | UInt16 | % | 0.01 | RW |
Read this device live with Modbus Connect, free for Windows, macOS and Linux
Related guides
Notes
Source: Belimo 'Modbus Interface Description - Air/water Actuators, General actuators for air and water', edition 2026-05 / V3.08, manufacturer date 05.09.2023 (belimo_Modbus-Register_AirWater_V3_8_en-gb.pdf). The vendor host www.belimo.com answers automated requests with HTTP 403, so the document was read from Belimo's own regional mirror https://www.belimo.ro/mam/general-documents/system_integration/Modbus/belimo_Modbus-Register_AirWater_V3_8_en-gb.pdf (same MAM document and edition); the URL above is the canonical vendor location. Covered actuator types: ..M(C)24A-MOD, ..R24A-MOD, ..V(K)24A-MOD, ..F24A-MOD, ..RF24A-MOD and ..H24A-MOD - the spring-return, modulating and fail-safe damper and valve actuators of the air/water range. Factory Modbus settings from the document: 38400 Bd, 1-8-N-2 (8 data bits, no parity, 2 stop bits), address 1; 9600/19200/76800/115200 Bd and 1-8-N-1 / 1-8-E-1 / 1-8-O-1 are selectable, as are addresses 1...247. Addressing: the document prints 'addressed by 1..n (Register No.) or 0..n-1 (Address)' with both columns on every row; the values here are the Address column (one less than the Register No.), hence zero_based. All registers are unsigned 16-bit; there are no 32-bit values in this map, so word order only matters if a reader adds them later (Belimo stores 32-bit values LSW first, hence LowFirst). Deliberately left out: registers 6, 7, 9, 10, 11, 110 and 111-117, which the document prints as '–'. This map is not the VAV-Compact or PR map: it has no volumetric-flow or delta-pressure block, and instead carries the electronic fail-safe registers 190/191 that the other ranges do not have. Sensor 1 value is entered with the millivolt unit and no scaling because the unit and the scale follow register 107 (millivolt 1:1, ohm 1:1, switch 0/1, PT1000/NI1000/NTC10K2 in degrees x0.1).