Sinclair SCC-36 User Manual page 7

Wiring Instructions:
3.2.3
Connection Method of L-CAC&Split unit (Modbus network)
(1) The centralized controller is applicable to UNI SPLIT units, One
The central controller has two ways to connect with the system:
centralized controller can control up to 36 UNI SPLIT units.
Method 1：The centralized controller Connect with UNI SPLIT Unit
(2) If the centralized controller is to be connected with UNI SPLIT units,
（Modbusnetwork）according to the below.
connect according to fig.3–7. The controller must connect with terminal unit of
UNI SPLIT system .Connect the centralized controller's A3 and B3 ports to
COM_BMS port on the UNI SPLIT unit correspondingly with
communication cords. A matching resistance needs to be added with the
communicationcords at the A3 and B3 ports. There are two COM_BMS
ports (two coreneilsbed and no polarity) on mainboard of UNI SPLIT unit,
one for centralized controller and another for UNI SPLIT unit connection.
Figure 3-7 Centralized Controller Connected with UNI SPLIT Unit