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4.8 Control using switched and 0-10V signals
An external controller that provides 24V AC switched signals or has a set of voltage-free relay contacts should be connected
as per the diagram below. UC8 inputs ‘
VF
’ and ‘
VC
’ will accept a 0-10V capacity control signals. If no capacity control signal is
available then link UC8 terminals ‘
VF
’ and ‘
5’
and ‘
VC
’ and ‘
12
’.
BMS / external controller
Capacity
UC8
0-10V
0V
HIGH
MEDIUM
LOW
COMP2
COMP1
HEA
T
HI ME LO C1
CP HT C2
12 VC 0V
24V AC or 12V DC
24V AC COM or 0V
5 VF 0V
0-10V
0V
Comp.
Fan
4.9 Control via Modbus RTU communications
OPA Econex units can be fully monitored and controlled via Modbus RTU serial communications. The following is typical for most
installations:
• Set DIP switches 11 and 12 OFF on all UC8 controllers.
• Connect BMS terminal A / TX+ to terminal A1 on all UC8 controllers.
• Connect BMS terminal B / TX- to terminal B1 on all UC8 controllers.
It is recommended to ‘daisy-chain’ the A&B connections using shielded twisted pair type cable, suitable for RS485
communications. Signals A and B should form one twisted pair. The cable shield should connect to terminal ‘0V’ on the UC8
controller. The Master/Slave communications cable connected between the UC8 controllers must be removed.
DIP switch 11 must be set to OFF on both UC8 controllers.
• To avoid collisions of messages on the RS485 serial communications cable it is necessary to ensure each connected UC8
controller has a unique Modbus device address. Refer to section
4.10
for the procedure.
Example:
For detailed information about monitoring and control via Modbus RTU refer to document “UC8 Modbus communications”,
available free on the temperzone.biz or .com website.
4.10 Setting the UC8 Modbus device address
To view or change the Modbus device address of a UC8 follow these steps:
• Power up the unit but leave the compressors off.
• Hold down the SW3 pushbutton on the UC8 circuit board u
ntil the display shows:
‘0’ [release] ‘1’ short press to ‘2,’ [long press] A, [long press]
• The display will show the current Modbus device address. The factory default address is ‘44’. [Short press]
the button to select
higher numbers, for example press once to change the address to 45, press twice for address 46 and so forth.
[Long press] to
save the chosen address. After address 99 the number returns back to 1.
• The controller returns to the default state
(– ●)
.
