Specifications

28 Centrifugal Chillers IMM WMC-2
Multiple Chiller Setup
WMC dual compressor units have their main control components factory wired to an internal network so that
the components can communicate with each other, within the chiller itself.
On multi-chiller WMC applications, two WMC chillers can be interconnected by simple field RS485
interconnecting wiring, the addition of an accessory communication isolation board(s) 485OPDR (McQuay P/N
330276202), and some MicroTech II control settings. The 485OPDR isolation board can be purchased with the
unit or separately, during or after chiller installation. Only one board is required required. WMC chillers
cannot be interconnected with WSC, WDC, or WCC chillers.
Communication Setup
Interconnecting MicroTech II pLAN RS485 wiring should be installed by the installing contractor prior to start-
up. The McQuay start-up technician will check the connections and make the necessary set point settings.
1. With no pLAN connections between chillers, disconnect chiller control power and set the DIP switches as
shown in Table 12.
2. With all manual switches off, turn on control power to each chiller and set each OITS address (see Note 2 on
page 28).
3. Verify correct nodes on each OITS Service Screen.
4. Connect chillers together (RS485 wiring) as shown in Figure 16. The first chiller in the connection can be
designated as Chiller A. The isolation board is attached to the DIN rail adjacent to the Chiller A unit
controller. The isolation board has a pigtail that is plugged into J10 on the controller. Most chillers will
already have a universal communication module (UCM) that connects the controller to the touchscreen
already plugged onto J10. If this is the case, plug the isolation module pigtail into the empty RJ11 pLAN
port on the UCM. This is equivalent to plugging into the unit controller directly.
Next, interconnecting wiring is needed between Chiller A and Chiller B.
Interconnection: Belden M9841 (RS 485 Spec Cable) is wired from the 485OPDR isolation board
(terminals A, B, and C) on Chiller A to the J11 port on the unit controller of Chiller B. At J11, the shield
connects to GND, the blue/white wire to the (+) connection, and the white/blue to the (-) connection.
Note that Chiller B does not have, or need, an isolation board.
5. Verify correct nodes on each OITS Service Screen.
Table 12, Address DIP Switch Settings for Controllers Using pLAN.
Chiller
(1)
Comp 1
Controller
Comp 2
Controller
Unit
Controller
Reserved
Operator
Interface (2)
Reserved
1 2 5 6 7 8
A
100000 010000 101000 011000 111000 000100
9 10 13 14 15 16
B
100100 010100 101100 011100 111100 000010
NOTES:
1. Up to four single or dual compressors can be interconnected.
2. The Operator Interface Touch Screen (OITS) setting is not a DIP switch setting. The OITS address is selected by
selecting the ‘service’ set screen. Then, with the Technician level password active, select the ‘pLAN Comm’ button.
Buttons A(7), B(15), C(23), D(31) will appear in the middle of the screen, then select the letter for the OITS address for
the chiller that it is on. Then close the screen. Note that A is the default setting from the factory.
3. Six Binary Switches: Up is ‘On’, indicated by ‘1’. Down is ‘Off’, indicated by ‘0’.