30
Centrifugal Chillers
IM 1044-2
In the event a transformer supplies control voltage, it must be rated at 3 KVA, with an inrush rating of 12 KVA
minimum at 80% power factor and 95% secondary voltage. For control wire sizing, refer to NEC. Articles 215
and 310. In the absence of complete information to permit calculations, the voltage drop should be physically
measured.
Table 13, Control Power Line Sizing
Maximum Length, ft (m)
Wire Size (AWG)
Maximum Length, ft (m)
Wire Size (AWG)
0 (0) to 50 (15.2)
12
120 (36.6) to 200 (61.0)
6
50 (15.2) to 75 (22.9)
10
200 (61.0) to 275 (83.8)
4
75 (22.9) to 120 (36.6)
8
275 (83.8) to 350 (106.7)
3
Notes:
1.
Maximum length is the distance a conductor will traverse between the control power source and the unit control panel.
2.
Panel terminal connectors will accommodate up to number 10 AWG wire. Larger conductors will require an
intermediate junction box.
The Unit On/Off switch located in the Unit Control Panel should be turned to the "Off" position any time
compressor operation is not desired.
Wiring for Optional BAS Interface
The optional Building Automation System (BAS) interface utilizing the MicroTech II unit controller’s
Open Choices
feature is field wired and will be set-up by the
Daikin
startup service technician. The
following manuals (available on
www.DaikinApplied.com
) explain the wiring and mounting
procedures:
L
ON
W
ORKS
> IM 735
BACnet
> IM 906
MODBUS
> IM 743
Flow Switches
Water flow interlock terminals are provided on the Unit Control Panel terminal strip for field-mounted
switches. See the Field Wiring Diagram on page 32 or on the cover of the control panel for proper connections.
The purpose of the water flow interlocks is to prevent compressor operation until such time as both the
evaporator water and condenser water pumps are running and flow is established. If flow switches are not
furnished factory-installed and wired, they must be furnished and installed by others in the field before the unit
can be started.
System Pumps
Operation of the chilled water pump can be to 1) cycle the pump with the compressor, 2) operate continuously,
or 3) start automatically by a remote source.
The cooling tower pump must cycle with the machine. The holding coil of the cooling tower pump motor
starter must be rated at 115 volts, 60 Hz, with a maximum volt-amperage rating of 100. A control relay is
required if the voltage-amperage rating is exceeded. See the Field Wiring Diagram on page 32 or in the cover
of control panel for proper connections.
All interlock contacts must be rated for no less than 10 inductive amps. The alarm circuit provided in the
control center utilizes 115-volts AC. The alarm used must not draw more than 10 volt amperes.
See OM CentriMicro II for MicroTech II unit controller details.
Control Panel Switches
Three On/Off switches are located in the upper left corner of the main Unit Control Panel, which is adjacent to
the operator interface panel, and have the following function:
•
UNIT shuts down the chiller through the normal shutdown cycle of unloading the compressor(s) and
provides a post-lube period.
•
COMPRESSOR one switch for each compressor on a unit, executes an immediate shutdown without the
normal shutdown cycle.
•
CIRCUIT BREAKER disconnects optional external power to system pumps and tower fans.