Application guidelines
32
FRCC.PC.021.A5.22
CAN-Bus and Modbus RS485 Communication
Measurements
The signal content is as in following exemple:
Pc = 23.5678 bar absolute
Scaled value: 23.5678*10000 = 235678 (same in
hexadecimal form: 0x0003989E)
Low word: 0x989E (decimal value = 39070)
High word: 0x0003 (decimal value = 3)
This OCS will broadcast these pressures to all the
other OCS of the compressor rack. A transmission
period of max 2 seconds is recommended.
OCS will detect Modbus communication timeout
after 3 seconds. In this case:
• If a backup transmitter is connected to
another OCS board, then the local signal will
be used and this backup transmitter will start
broadcasting.
• If no backup transmitter is present in the rack,
all compressors will be stopped.
Variable
Register
Description:
Note
Hex
Dec
AI_Pc_x10
Measured condensing pressure
0x3900
14592
AI_Pe_x10
Measured evaporating pressure
0x3901
14593
Tc_x10
Calculated condensing temperature
0x3902
14594
Te_x10
Calculated evaporatinging temperature
0x3903
14595
Liq_Ctrl_ref_x10
Injection control temperature
0x3906
14598
Liq_Ctrl_error_x10
Injection control error
0x3907
14599
Liq_valve_OD_x10
Valve opening degree %
0x3908
14600
Map_pos
Possition on operating envelope area
0x3909
14601
MaxDischargeTemp_log
Max. discharge temperature time counter
0x390A
14602
MinSucPressure__log
Min. suction pressure time counter
0x390B
14603
HighPressureRatio_log
High pressure ratio time counter
0x390C
14604
LowPressureDiff_log
Low pressuredifference time counter
0x390D
14605
MaxTimeStartMode_log
Max. time start mode time counter
0x390E
14606
DO_Start
Relay output status for Contactor switch
0x390F
14607
DO_SurfaceSumpHeater
Relay output status for Sumpheater
0x3910
14608
DI_status
bit 6: DI_SSH_failure
bit 5: DI_wrong_phase_sequence
bit 4: - not used
bit 3: - not used
bit 2: DI_Phase_loss
bit 1: DI_compr_Stopped
bit 0: DI_PTC_alarm
0x3912
14610
PTC_resistance_x4
PTC measurement [ohm]
(when compressor is off)
0x3913
14611
SSH_mA_V
SSH measured value
SSH ON: [mA],
SSH OFF: [Volt]
0x3914
14612
ComprRunStatus
0: stopped 1: running
0x3915
14613