FläktGroup FG_DC_9703GB_20210222_R3
Specifications are subject to alteration without notice
PI FUNCTION MODBUS COMMUNICATION
CHILLED BEAMS
PI FUNCTION (OPTION)
For Demand Controlled Ventilation operation, the Pi Function accessory
must be mounted on the chilled beam. Thanks to this function, an
actuator will then change automatically the nozzle position in order to
change primary airflow.
The chilled beam system will be able to follow different operation se-
quences depending on the controller chosen. It is possible to set dif-
ferent airflows according to occupancy level or to manage air quality
thanks to a CO2 sensor connected to the controller. Three parameters
can be set in the actuator : V
0
for non-occupancy, V
min
for standard
occupancy and V
max
(boost) for high occupancy level.
Combined with the STRA-24 room controller, different modes are of-
fered : OFF, Standby, unoccupied, occupied and boost. For each mo-
des, different sequences between water and air are possible: cooling
without free cooling, cooling with free cooling and airflow depending
on CO
2
.
The Pi function keeps airflow at set point value despite pressure fluctu-
ations in the duct. The Pi Function is easy to retrofit and applicable to
any ductwork system owing to its pressure independent functionality.
Note. When using Pi Function, induction is always symmetrical and a
room controller is required to operate Pi Function with link to occupan-
cy sensor. Duct pressure has to be maintained between 40 and 140 Pa.
Caution! If Pi Function is installed as a retrofit, there is no need for
a damper before the chilled beam. Any previously installed damper,
should be set to fully open position or removed.
Room controller signal (V)
V0
Non-occupancy
airflow
Occupancy
Min. airflow
Vmin
(Boost mode)
Occupancy
Max. airflow
Vmax
Actuator
airflow setting
2
01
0
Pi-function Modbus communication
2
FläktGroup FG_DC_9703GB_20210222_R3
Specifications are subject of alteration without further notice
MODBUS INSTALLATION
1. Connect A and B (2 white cables).
2. Default Modbus address is 1. If you would like to change the
address, then turn right knob to address and then the actual
address is displayed on screen.
Display number EEPROM-value Baudrate Parity Stop bits
1 0 9600 none 2
2 1 9600 even 1
3 2 9600 odd 1
4 3 19200 none 2
5 4 19200 even 1
6 5 19200 odd 1
7 6 38400 none 2
8 7 38400 even 1
9 8 38400 odd 1
3. Then select address with value selector. Address flashes on screen
when selected.
4. Set baudrate 19200, 8 Data bits, Parity Even, 1 stop bit.
5. If another baudrate want to be used then factory setting (19200, 8
Data bits, Parity Even, 1 sto) bit), baudrate can be selected direct on
display as described below
6. Modbus address is chosen according to description above and after
the address is confirmed by 2 flashing, the value selector is turned
to end stop “+”. The displays shows “2 in” which indicates the se-
cond level. At second level Baudrate can be selected according to
“display number” in table below. When value is selected, display
flashing 2 times to confirm the new value.
7. Baudrate can also be selected with Modbus parameter 568 with
use of same table below.
OPERATING VALUES
Name Address decimal Data Type Value range r/w Description Memory def. value
Set point 0Word 0…10000 r/w
Setpoint [%]
0…100% ’0’: set point is read only
When the override control is activated,
value in register will be -1.
Vmin = 0% Vmax 100 %
RAM
Override control 1Word 0…5 r/w
Override control
’0’ - - - ’1’ open
’2’ close ’3’ min
’4’ max ’5’ V0
RAM
Command 2Word 0…4 r/w
Command
’0’ - - - ’1’ adaption
’2’ - - - ’3’ - - -
’4’ controller reset
RAM
Device ID 3Word 0…7 r
Device ID
’0’ - - - ’1’ standard actuator
’2’ VAV ’3’ fire damper
’4’ GUAC VAV ’5’ GUAC CM
’6’ GT ’7’ PICB
EEPROM 7
Relative position 4Word 0…10000 rRelative position [%]
0...100.00 RAM
Relative flow 6 Word 0…10000 rFlow [%] 0…100 scaled to Vmax
100% = sqrt(150) × K100% RAM
Absolute flow 7Word 0…65535 rFlow [l/s] RAM
Warning!
If the actuator is in the startup mode, all
service values cannot be changed.
When address 2 (command) changes the
operating value to '0', startup procedure is
finalized.
Pi-function Modbus communication
3
FläktGroup FG_DC_9703GB_20210222_R3
Specifications are subject of alteration without further notice
HOLDING REGISTER SERVICE VALUES
Name Address decimal Data Type Value range r/w Description Memory def. value
Serial number 1 100 Word 101...991 2 rserial number JJMM EEPROM
-
Serial number 2 101 Word 100...312 3 rserial number DDHH EEPROM
-
Serial number 3 102 Word 01...5959 9 rserial number MMSSXX = test number EEPROM
-
Software version 103 Word 1...65535 rsoftware version EEPROM
-
Service information 104 Word 0...65535 rsee table status-register RAM
V0 value absolute 119 Word 0...65535 r/w V0 value (m3/h)(l/s)(pa) Integer value EEPROM
5
min value absolute 120 Word 0...65535 r/w min value (m3/h)(l/s)(pa) Integer value EEPROM
10
max value absolute 121 Word 0...65535 r/w max value (m3/h)(l/s)(pa) Integer value EEPROM
20
Mode signal set point
analog output 122 Word 0...3 r/w
Value Referencing signal Analog out
EEPROM
0
0Analog in 1 Actual flow (V)0..10
1Communication via
Modbus register 0 Actual flow (V)0..10
2Communication via
Modbus register 0
Value written in
register 10
3Analog in 1 Value written in
register 10
Device address 130 Word 1 -247 r/w Device address 1 - 247 EEPROM
1
K 100% 221 Word 0..9990 r/w K 100% Value EEPROM
40
Attention!
Please be aware that the "EEPROM" has
limited capacity to accept changes. Excessive
alterations will result in EEPROM failure.
STATUS REGISTER ADRESS 104
Bit number Bit name Function / Status
Bit 0 bepf 1 ! eeprom error checksum 1
Bit 1 bepf 2 ! eeprom error checksum 2
Bit 2 bauf 1 Kat1 free for write
Bit 3 bauf 2 Kat2 free for write
Bit 4 bfaterr fatal EEPROM-error, device is inoperable
Bit 5 bblock ! 1 = block detected
Bit 6 bschleich 1 = seepage flow detected
Bit 7 bfahrt 1 = motor drive
Bit 8 -not used
Bit 9 -not used
Bit 10 -not used
Bit 11 bMotor Timeout 1 = motor max running time expired. Motor running in one direction and does not reach an end position or dead band.
/
