Operation
www.DaikinApplied.com 35
IOM 1274-3 • CENTRIFUGAL WATER CHILLERS
Operation
WARNING
Electric shock hazard. Can cause personal injury or equipment
damage. This equipment must be properly grounded.
Connections to and service of the MicroTech control panel
must be performed only by personnel that are knowledgeable
in the operation of the equipment being controlled.
CAUTION
Static sensitive components. A static discharge while handling
electronic circuit boards can damage components. Discharge
any static electrical charge by touching the bare metal inside
the control panel before performing any service work. Never
unplug any cables, circuit board terminal blocks, or power
plugs while power is applied to the panel.
CAUTION
Do not install any non-Daikin Applied authorized software or
alter operating systems in any unit microprocessor, including
the interface panel. Failure to do so can cause malfunction of
the control system and possible equipment damage.
Dual/Multi-Chiller Operation
Multiple Chiller Setup
Single compressor chillers WSC and dual compressor chillers
WDC and WCC have their main control components factory
wired to an internal pLAN network so that the components
can communicate with each other, within the chiller itself. On
multi-chiller applications, up to four chillers, either single, or
dual compressor, can be interconnected by this internal pLAN.
All that is required is simple field RS485 interconnecting wiring,
the addition of accessory communication isolation board(s)
485OPDR (Daikin Applied P/N 330276202), and MicroTech
II control settings. (If applicable, additional WCC instructions
should be referenced in the current Installation, Operation, and
Maintenance manual for dual centrifugal chillers.). The isolation
board can be purchased with the unit or separately, during or
after chiller installation. The number of boards required equals
the number of chillers minus one.
NOTE:
pLAN multiple chiller interconnection is designed
for parallel chiller installations with the leaving water
sensors in their normal location in the outlet nozzle.
For two units in series operation, the leaving chilled water
sensors must be moved far enough downstream from the last
chiller to insure reading a thoroughly mixed water temperature.
Passing through one or two elbows will usually suffice. Series
chillers are normally single pass resulting in undesirable
temperature stratification at the outlet nozzle.
Connectability
Centrifugal models WSC and WDC of various vintages with
MicroTech controllers can be interconnected, but all must be
loaded with the most recent control software.
Responsibilities
Unless otherwise stated in the contract documents, the
interconnecting MicroTech pLAN RS485 multiple chiller wiring
between chillers is the responsibility of the installing contractor
and should be completed prior to startup. The Daikin Applied
startup technician is responsible for checking the wiring and
making the appropriate control changes.
pLAN Wiring
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 compressor controller. The isolation board has a
pigtai 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
into J10. If this is the csae, plug the isolation module pigtail into
the empty RJ11 pLan port on the UCM. This is equivalent to
plugging into the unit controller directly.
Two Chillers:
If only two chillers are to be connected, Belden
M9841 (RS 485 Spec Cable) is wired from the isolation board
(terminals A, B, & C) on Chiller A to the J11 port on the unit
controller of Chiller B. At J11, The shield connects to the GND,
the blue/white wire to the center (+) connection, and the white/
blue to the (-) connection. Note that Chiller B does not have an
isolation board. The last chiller (B in this case) to be connected
does not need an isolation board.
Three or Four Chillers:
If three or four chillers are to be
connected, the interconnecting wiring is still made to B’s J11
port. The second chiller (Chiller B) must have an isolation
board that will be plugged into Chiller B’s UCM pLAN port.
Chiller B will look like Chiller A. The wiring from Chiller B to
Chiller C will be the same as Chiller A to B. That is, Belden
cable connects from A, B, and C on B’s isolation board to
Chiller C’s J11 port. Chiller C has no isolation board. The
procedure is repeated to the fourth chiller if four chillers are
interconnected.
Figure 35: pLAN Communication Wiring
