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Protective Devices
COMPRESSOR PROTECTION
Overcurrent
Each compressor has internal line break motor protection.
Overtemperature
Each compressor has an internal protector to protect it against
excessively high discharge gas temperatures.
High-Pressure Switch
If the high-pressure switch trips, the compressor will shut
down and the Circuit A High Pressure Alert will activate. Re-
fer to the alarm section for the High pressure alert.
EVAPORATOR FAN MOTOR PROTECTION
In the belt drive application, the VFD serves as the motor ther-
mal and over-current protection. Refer to page 48 for more de-
tail on the VFD.
CONDENSER-FAN MOTOR PROTECTION
The ECM motor is protected from locked rotor and over-cur-
rent protection through the electronic control module attached
to the motor.
SATURATED SUCTION PRESSURE (SSP)
If the SSP for a particular circuit is reading below the alarm set
point for an extended period of time, that circuit will be shut
down. After 15 minutes, the alarm will automatically reset. If
this alarm occurs 3 times consecutively, the circuit will remain
locked out until an alarm reset is initiated via CCN or manually
via the SystemVu™ controller display (see “Faults and Alerts”
on page 32 for more details).
CONDENSATE OVERFLOW SWITCH (COFS)
A separate factory-installed device can detect a full drain pan.
This device consists of a pan sensor to detect the water level
and a relay control switch to read the sensor. The control
switch is located in the unit control box and feeds into the Sys-
temVu control to trip a condensate overflow fault. The relay
switch is a normally open device that closes when power is ap-
plied. If the sensor detects high water levels for 10 seconds
straight, it will open the contact removing the input provided to
the SystemVu control. The switch will also turn its red LED
on. If the water level is low enough for 5 minutes, the relay will
close again applying the input back to the SystemVu controller.
A blinking red LED on the switch indicates that the sensor has
been disconnected.
Space Mounted Sensors
SPACE TEMPERATURE SENSOR (T-55)
The T-55 space temperature sensor (part no. 33ZCT55SPT) is a
field-installed accessory. The sensor is installed on a building in-
terior wall to measure room air temperature. The T-55 sensor
also includes an override button on the front cover to permit oc-
cupants to override the Unoccupied Schedule (if programmed).
TB5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Input
TB5-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Common
SPACE TEMPERATURE SENSOR (T-56)
The T-56 space temperature sensor (part no. 33ZCT56SPT) is a
field-installed accessory. This sensor includes a sliding scale
on the front cover that permits an occupant to adjust the space
temperature set point remotely. The T-56 sensor also includes
an override button on the front cover to allow occupants to
override the unoccupied schedule (if programmed).
TB5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Input
TB5-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Common
TB5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . Setpoint Offset Input
SPACE TEMPERATURE SENSOR AVERAGING
See Fig. 39 for space temperature averaging with T-55 sensors
only. If the use of one T-56 sensor is required, refer to Fig. 40.
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution may result in unit damage.
DO not bypass the VFD while running the motor. Do not
change VFD parameter associated with motor characteris-
tics, these are factory programmed for motor protection.
Damage to the motor or the VFD can occur.
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