Specifications

14
1. Cut the CCN wire and strip ends of the red (+), white
(ground), and black (–) conductors. (If another wire color
scheme is used, strip ends of appropriate wires.)
2. Insert and secure the red (+) wire to terminal 5 of the
space temperature sensor terminal block.
3. Insert and secure the white (ground) wire to terminal 4 of
the space temperature sensor.
4. Insert and secure the black (–) wire to terminal 2 of the
space temperature sensor.
5. Connect the other end of the communication bus cable to
the remainder of the CCN communication bus.
Energy Management Module (Fig. 10) — This
factory-installed option (FIOP) or field-installed accessory is
used for the following types of temperature reset, demand
limit, and/or ice features:
• 4 to 20 mA leaving fluid temperature reset (requires
field-supplied 4 to 20 mA generator)
• 4 to 20 mA cooling set point reset (requires field-
supplied 4 to 20 mA generator)
• Discrete inputs for 2-step demand limit (requires field-
supplied dry contacts capable of handling a 24 vac,
50 mA load)
• 4 to 20 mA demand limit (requires field-supplied 4 to
20 mA generator)
• Discrete input for Ice Done switch (requires field-
supplied dry contacts capable of handling a 24 vac,
50 mA load)
See Demand Limit and Temperature Reset sections on
pages 23 and 21 for further details.
Loss-of-Cooler Flow Protection — A proof-of-
cooler flow device is factory installed in all chillers.
Condenser Flow Protection — A proof-of-condens-
er flow protection accessory can be field installed in the con-
denser water piping of all chillers. The unit must be configured
for the input to be enabled.
Thermostatic Expansion Valves (TXV) — All
units are equipped from the factory with conventional TXVs.
The 30MPA units and 30MPW units with medium temperature
brine also have factory-installed liquid line solenoids. The liq-
uid line solenoid valves are not intended to be a mechanical
shut-off. For 30MPW units, when service is required, recover
the refrigerant from the system.
For 30MPA units when service is required, the compressor
and evaporator can be serviced by closing the factory-installed
liquid line service valve and field-installed discharge line ser-
vice valve. After the valves are closed, recover the refrigerant
from the system.
The TXV is set at the factory to maintain approximately 8 to
12° F (4.4 to 6.7° C) suction superheat leaving the cooler by
monitoring the proper amount of refrigerant into the cooler. All
TXVs are adjustable, but should not be adjusted unless abso-
lutely necessary.
Capacity Control — The control system cycles com-
pressors, digital scroll modulating solenoid (if equipped), and
minimum load valve solenoids (if equipped) to maintain the
user-configured leaving chilled fluid temperature set point. En-
tering fluid temperature is used by the main base board (MBB)
to determine the temperature drop across the cooler and is used
in determining the optimum time to add or subtract capacity
stages. The chilled fluid temperature set point can be automati-
cally reset by the return fluid temperature, space, or outdoor-air
temperature reset features. It can also be reset from an external
4 to 20-mA signal (requires energy management module FIOP
or accessory).
The capacity control algorithm runs every 30 seconds. The
algorithm attempts to maintain the Control Point at the desired
set point. Each time it runs, the control reads the entering and
leaving fluid temperatures. The control determines the rate at
which conditions are changing and calculates 2 variables based
on these conditions. Next, a capacity ratio is calculated using
the 2 variables to determine whether or not to make any
changes to the current stages of capacity. This ratio value
ranges from –100 to +100%. If the next stage of capacity is a
compressor, the control starts (stops) a compressor when the
ratio reaches +100% (–100%). If installed, the minimum load
valve solenoid will be energized as the last stage of capacity
before turning off the last compressor. A delay of 90 seconds
occurs after each capacity step change. Refer to Table 9.
MINUTES LEFT FOR START — This value is displayed
only in the network display tables (using Service Tool,
ComfortVIEW™ or ComfortWORKS
®
software) and
represents the amount of time to elapse before the unit will start
its initialization routine. This value can be zero without the
machine running in many situations. This can include being
unoccupied, ENABLE/OFF/REMOTE CONTACT switch in
the OFF position, CCN not allowing unit to start, Demand
SPT (T10) PART NO. 33ZCT55SPT
SENSOR
SEN
SEN
LVT
3
4
Fig. 8 — Typical Space Temperature
Sensor Wiring
a30-4968
T-55 SPACE
SENSOR
CCN+
CCN GND
CCN-
TO CCN
COMM 1
BUS (PLUG)
AT UNIT
1
2
3
4
5
6
Fig. 9 — CCN Communications Bus Wiring
to Optional Space Sensor RJ11 Connector
CAUTION
Care should be taken when interfacing with other manufac-
turer’s control systems due to possible power supply
differences, full wave bridge versus half wave rectification.
The two different power supplies cannot be mixed.
ComfortLink controls use half wave rectification. A signal
isolation device should be utilized if a full wave bridge sig-
nal generating device is used.