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The "On/Off" and "Cold/Hot" controls
should be set:
- Only on the GR3 Master board using
the keyboard, if the machine is in Local
mode
- Through the BMS, if the machine is in Re-
mote mode.
NOTE
THE SLAVE BOARD CAN HAVE A DELAY OF
APPROXIMATELY 20" FROM THE OFF COM-
MAND.
6. 1
SETPOINT
There is only one settings menu; use the ar-
row keys to move between settings.
(see TAB 6. 1 . 1 )
6.2
REGULATING
THE THERMOSTAT
The water temperature is regulated by the
pCO board, which reads the settings on the
GR3 "Master" board and sends a power re-
quest (0-100%) to the two chillers through
serial communication. Each chiller receives
the power request and controls the rota-
tion of its compressors independently.
Chiller rotation is controlled by the pCO ac-
cording to the sum of all the compressors'
working hours (the sum is divided by 10,
so if the sum is less than 10 the "master"
chiller is always the first to start and the
last to stop).
Temperature regulation can take place at
the water's inlet or outlet, depending on the
settings on the GR3 board.
In/Usc H 2 0 Chiller type
In
NRA/NRC
In
NBW/NLW
Out
NRA/NRC
Out
NBW/NLW
6
ON/OFF AND COLD/HOT CONTROLS
6. 1 . 1
Description of settings
SETTING
Protocol
Serial Addres
Baund rate
Step
Pump off with
compressor off
Machine type
Master
In/Usc H20.
The probe used is shown in the table and
depends on the situation (see table below).
Regulation at the output is proportional +
integrated, with the integration time as set
on the GR3 Master board:
Time Int
When determining thermostat operations,
the GR3 Master board always considers
the following setpoints:
Cold set
Hot set
2° C Set
2° H Set
Tot.Diff.
For reasons of consistency, all the setpoints
changed on the "master" are also updated
on the "slave". If the user makes the chang-
es on the "slave" board, they will be over-
written, and the changes (which in any case
have no effect) will be lost. The power re-
Cold operation
SIW (M21 1-2 Master)
B4 Dualchiller (da posizionare sul comune delle uscite evaporatori)
B5 Dualchiller (to be placed on common condensers
output)
DESCRIPTION
Supervision protocol (BMS
Serial address supervision
Communication speed
Maximum difference in power requests to
both chillers (master and slave) from pCO
controller
NOT USED
Machine type Condensation/Evaporation
quest is sent to the chillers as shown in the
examples below (at cold temperature, with
proportional regulation only, C1 = chiller
with less working hours). The Step setting
that arranges the chillers in parallel or in
cascade is: STEP 25% (default).
The default Step value provides uniform sys-
tem control and prevents problems caused
by the evaporators being connected in par-
allel (having a low temperature adjusted to
the common flow, with only one chiller run-
ning and maximum water flow, means hav-
ing very low temperatures at the working
machine's evaporator outlet), while at the
same time allowing minimum machine rota-
tion, so that one chiller can even be switched
off during periods of low requirement.
NOTE
Chiller rotation is not affected by alarms
regarding the chillers.
If all the circuits are on alarm, chiller re-
quests are brought to 0%
SIW (M21 1-2 Master)
B5 Dualchiller (to be placed on common condensers
DEFAULT
MIN
Modbus Carel485 Modbus
001
1
9600
1200
25 %
1%
NO
NO
Air/
Air/
Water
Water
Hot operation
SIWH (M22 1-2 Master)
output)
MAX
255
19200
100%
Yes
Air/
Water
11
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