Belimo · HVAC controller
PR actuator for butterfly valves (PR..A-BAC-..) 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 0 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. | UInt16 | - | 1 | RW |
| 2 | 1 | Command 0 = none (default). Actuator service and test functions; the register returns to none after the command has been sent. | 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 x0.1 for the PT1000 / NI1000 / NTC10K2 types. Range 0...65535. | UInt16 | mV | 1 | R |
| 9 | 1 | Sensor 2 value Same conversion rules as sensor 1, following sensor type 2 (register 114). 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 |
| 106 | 1 | Max Upper position limit, range Min+3000...10000 (Max has to be at least Min + 30 percent). Default 10000. This range has no Min register. | 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. | 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 |
| 114 | 1 | Sensor 2 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. | UInt16 | - | 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. The actuator stays in position for this time 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 taken after a power failure, respecting the bridging time. Range 0...10000. The rotary knob must be in the tool position. | UInt16 | % | 0.01 | RW |
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Related guides
Notes
Source: Belimo 'Modbus Interface Description - PR Actuator, Rotary actuator for butterfly valves', edition 2026-01 / V3.08, manufacturer date 01.12.2023 (belimo_Modbus-Register_PR_V3_8_en-gb.pdf). www.belimo.com refuses automated downloads (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_PR_V3_8_en-gb.pdf (same MAM document and edition); the URL above is the canonical vendor location. Actuator type: PR..A-BAC-.. (butterfly valve actuators). Factory Modbus settings: 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: 'addressed by 1..n (Register No.) or 0..n-1 (Address)' with both columns on every row, so the stored values are the Address column, i.e. zero_based. This map is not the air/water actuator map: the PR range has two sensor inputs (registers 8/9 with types 107 and 114), carries only a Max limit (register 106, at least 30 percent above an implicit minimum) and no Min register (register 105 is printed as '–'), and its fail-safe registers sit at 190/191 as on the air/water range. All values are unsigned 16-bit; there are no 32-bit rows, so word order only matters if a reader later adds them (Belimo stores 32-bit values LSW first, hence LowFirst). Left out: registers 6, 7, 10, 11, 105, 110-113, 115-117, all printed as '–'. Sensor values are entered with the millivolt unit and no scaling because the unit and the scale follow the configured sensor type (millivolt 1:1, ohm 1:1, switch 0/1, temperature types x0.1).