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Danfoss VLT HVAC Drive FC 102 Modbus register map

VLT HVAC Drive FC 102 (1.1-90 kW) over the built-in RS485 port, Modbus RTU with the FC control profile

  • Official
  • 42 registers
  • Modbus RTU
  • Revision 1 · 2026-10-18

Official: Written from the manufacturer's documentation, but not tested on a device yet. Check the map against the manufacturer's documentation before you write to a live device. Tested it? Report a test.

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Communication

Protocol
Modbus RTU
Unit ID
1default
Serial
9600 8E1 · 9600 baud, 8 data bits, even parity, 1 stop bit
Byte / word order
ABCD · bytes big-endian, words high first
Addresses
1-based · wire address = address − 1

Connection values are defaults: the device may be configured differently.

Map

Registers
41 holding registers, 1 coil
Groups
5
Revision
1 · 2026-10-18
Added
()
File
maps/danfoss/fc-102.mbmap.json · 13 KB · history
SHA-256
4afc99895950eeca45c790d28502f073520f978b949ab744cd15c0c24611c036
Manufacturer
danfoss.com

Sources and notes

Source: Danfoss, "VLT HVAC Drive FC 102 1.1-90 kW Design Guide", MG11BC22 (06/2014); https://assets.danfoss.com/documents/272740/AJ299549559248en-US1801.pdf

  • Holding register of parameter x-yy is 10 times its number: 3-12 is register 3120, 8-30 is register 8300. Array parameters need the index in register 9 first.
  • Registers and coils are numbered from 1 in the guide, and the bus address is one less (register 50000 is sent as 49999), so this map uses address_base 1.
  • Control word, bus reference, status word and main actual value sit at registers 50000, 50010, 50200 and 50210.
  • This map lists the registers the design guide describes and a few parameters it uses as examples. The other parameters, their sizes and conversion indexes are in the FC 102 programming guide; a 32-bit parameter takes two registers.
  • The guide also describes the control word and status word as coils (1 to 16 and 33 to 48); they are not in this map, use the registers instead.
  • To enable Modbus: 8-30 Protocol = Modbus RTU, 8-31 Address 1 to 247, 8-32 Baud rate 2400 to 115200, 8-33 even parity with 1 stop bit by default.
  • Function codes: 1, 3, 5, 6, 15 and 16, plus 11, 17 and the diagnostics function 8.
AreaAddressNameTypeAccessUnitScaleDescription
HR 7 uint16 R Last error code from an FC data object interface
HR 9 uint16 RW Index used for the next access to an array parameter; set it before reading or writing one
HR 50000 uint16 RW FC profile control word (8-10 Control Profile = FC profile)
HR 50000 uint16 bits 0–1 RW Chooses one of the four values of 3-10 Preset Reference (bits 0 and 1)
HR 50000 bool bit 2 RW 0 = DC brake and stop, 1 = ramp
HR 50000 bool bit 3 RW 0 = coast to a stop, 1 = no coasting
HR 50000 bool bit 4 RW 0 = quick stop, 1 = ramp
HR 50000 bool bit 5 RW 0 = hold the present output frequency, 1 = use the ramp
HR 50000 bool bit 6 RW 0 = ramp stop, 1 = start
HR 50000 bool bit 7 RW Reset a trip on the rising edge
HR 50000 bool bit 8 RW 1 = run at the jog speed (3-19)
HR 50000 bool bit 9 RW 0 = ramp 1, 1 = ramp 2
HR 50000 bool bit 10 RW 1 = the drive uses the control word, 0 = it ignores it
HR 50000 bool bit 11 RW 1 = relay 01 on, if 5-40 Function Relay selects control word bit 11
HR 50000 bool bit 12 RW 1 = relay on, if 5-40 Function Relay selects control word bit 12. The text calls it relay 04 and the table relay 02
HR 50000 uint16 bits 13–14 RW Needs Multi Set-ups (bits 13 and 14)
HR 50000 bool bit 15 RW 1 = reverse
HR 50010 int16 RW % ×0.006103515625 Speed reference as a share of the maximum reference: 16384 (4000 hex) is 100 %, negative is reverse (two's complement)
HR 50200 uint16 R FC profile status word
HR 50200 bool bit 0 R
HR 50200 bool bit 1 R
HR 50200 bool bit 2 R 0 = coasting, 1 = enabled
HR 50200 bool bit 3 R 1 = tripped; reset to resume
HR 50200 bool bit 4 R
HR 50200 bool bit 6 R
HR 50200 bool bit 7 R
HR 50200 bool bit 8 R 1 = motor speed matches the reference
HR 50200 bool bit 9 R 1 = the drive can be controlled over the serial line, 0 = local operation
HR 50200 bool bit 10 R 0 = output frequency at the low or high speed limit
HR 50200 bool bit 11 R
HR 50200 bool bit 12 R 1 = stopped for inverter over-temperature and resumes by itself
HR 50200 bool bit 13 R
HR 50200 bool bit 14 R
HR 50200 bool bit 15 R
HR 50210 int16 R % ×0.006103515625 Actual output frequency in the same scale as the bus reference: 16384 (4000 hex) is 100 %
HR 3120 uint16 RW % ×0.01 Parameter 3-12; the manual's example: 1352 is 12.52 %
HR 4140 uint16 RW Hz ×0.1 Parameter 4-14; the manual's write example sends 1000 for 100 Hz
HR 8300 uint16 RW Set to Modbus RTU to use this map
HR 8310 uint16 RW
HR 8320 uint16 RW 2400 to 115200 baud, coded as in the programming guide
HR 8330 uint16 RW Default: even parity, 1 stop bit; coded as in the programming guide
CO 65 bool RW 0 = parameter changes go to RAM only, 1 = to RAM and EEPROM

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