22
If the 50TCQ unit has an economizer system and
free--cooling operation is required, a sensor representing
Return Air Temperature must also be connected
(field--supplied and installed). This sensor may be a T--55
Space Sensor (see Fig. 31) installed in the space or i n the
return duct, or it may be sensor PNO 33ZCSENSAT,
installed in the return duct. Connect this sensor to TB1--1
and TB1--3 per Fig. 32.
Configure the unit for Thermostat Mode — Connect to the
CCN bus using a CCN service tool and naviga te to
PremierLink Configuration screen for Operating Mode.
Default setting is Sensor Mode (value 1). Change the
value to 0 to reconfigure the c ontroller for Thermostat
Mode.
When the PremierLink is c onfigured for Thermostat
Mode, these functions a re not available: Fire Shutdown
(FSD), Remote Occupied (RMTOCC), Compressor Safety
(CMPSAFE), Supply Fan Status (SFS), and Filter Pressure
Switch (FILTER).
Economizer controls —
Outdoor Air Enthalpy Control (PNO 33CSENTHSW) --
The enthalpy control (33CSENTHSW) is avai lable as a
field--installed accessory to be used with the E conoMi$er2
dampe r system. The outdoor air enthalpy sensor is part of
the enthalpy control. (The separate field--insta lled
accessory return air enthalpy sensor (33CSENTSEN) is
required for differenti al enthalpy control . See Fig. 36.)
Loca te the enthalpy control in the economizer next to the
Actuator Motor. Locate two GRA leads in the factory
harness and connect the gray lead labeled “ESL” to the
terminal labeled “LOW”. See Fig. 36. Connect the
entha lpy control power input terminals to economizer
act uator power leads RED (connect to 24V) and BLK
(connect to GND).
7
ESL
CTB
ECON
LOW
GND
24V
Enthalpy
Switch
GRA
BLK
RED
Factory Wiring Harness
ECONO
MOTOR
C09026
Fig. 36 -- Enthalpy Switch (33CSENTHSW) Connections
The outdoor enthalpy changeover setpoint is set at the
enthalpy controller.
Differential Entha lpy Control — Differential enthalpy
control is provided by sensing and compa ring the outside
air and return air enthalpy conditions. Install the outdoor
air enthalpy control as described above. Add and install a
return air enthalpy sensor.
Return Air Enthalpy Sensor — Mount the return--air
entha lpy sensor (33CSENTSEN) in the return--air section
of the economizer. The return air sensor is wired to the
entha lpy controller (33CSENTHSW). See Fig. 37.
ESL
LOW
GND
24V
GRA
BLK
RED
ECONO
MOTOR
– 4-20
Main
+ VDC
Out
– 4-20 Main
Out
+ 24-36
VDC In
C09027
Fig. 3 7 -- Outside and Return Air Enthalpy Sensor
Wiring
To wire the return a ir enthalpy sensor, perform the
following:
1. Use a 2--c onductor, 18 or 20 AWG, twisted pair ca ble
to connec t the return air enthalpy sensor to the enthal-
py controller.
2. Connect the field--supplied RED wire to (+) spade
connec tor on the return air e nthalpy sensor and the
(+) terminal on the enthalpy controller. Connect the
BLK wire to (--) spade connector on the return air en-
thalpy sensor and the (--) terminal on the enthalpy
controller.
Indoor Air Quality (CO
2
sensor) — The indoor air quality
sensor accessory monitors space carbon dioxide (CO
2
)
levels. This information is used to monitor IAQ levels.
Several types of sensors are available, for wall mounting
in the space or in return duct, with and without LCD
display, and in combination with space temperature
sensors. Sensors use infrared technology to measure the
levels of CO
2
present in the space air.
The CO
2
sensors are all factory set for a range of 0 to
2000 ppm and a linear mA output of 4 to 20. Refer to the
instructions supplied with the CO
2
sensor for electrical
requirements and terminal locations. See Fig. 38 for
typical CO
2
sensor wiring schematic.
50TCQA
