Manual 2100-695C
Page
26 of 56
Liquid Pressure Transducer Alarm
When the liquid line pressure sensor value is out
of range (0-650 PSIG), the controller will generate
a sensor failure alarm to indicate the sensor is not
working properly.
This alarm is fixed and cannot be adjusted.
Liquid Temperature Sensor
The unit is equipped with a liquid line temperature
sensor to monitor the temperature of the liquid
refrigerant leaving the condenser and entering the EEV.
The temperature is measured with a 10k ohm NTC
thermistor.
The liquid temperature sensor can be verified and
adjusted by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to
I/O Config
;
press ENTER key.
4. Press UP or DOWN keys to scroll to
Liquid Temp
Sensor C2
.
5. Reference the
Value
to verify the temperature (see
Figure 41).
6. If an offset needs to be applied, press ENTER key
to scroll to
Offset
.
7. Press UP or DOWN keys to change the offset to
desired value.
8. Press ENTER key to save.
9. Press ESCAPE key several times to return to Main
Menu screen.
Condenser Fan Operation
Condenser Fan Speed Control
The unit is equipped with a variable speed ECM
(electronically commutated motor) condenser fan which
allows the unit to better control head pressures for
more efficient operation. The fan will speed up or slow
down to attempt to maintain a liquid line pressure.
The pressure setpoint that the fan will control to is
determined by the outdoor air temperature. The unit
will allow the liquid line pressure setpoint to increase
for high ambient scenarios or decrease for low ambient
scenarios. Because the control is dependent on both
the outdoor temperature sensor and the liquid line
pressure sensor, the controller will alter its operation
if a sensor is not enabled or failed. When the outdoor
temperature sensor is not enabled or is considered
failed by the controller, a nominal setpoint of 430
psi is used for fan control. When the liquid pressure
transducer is not enabled or is considered failed by the
controller, a nominal fan speed will be used during a
compressor cal (see Figure 42).
The condenser fan requires the compressor to be
running in order to operate.
High Pressure Control
Condenser Fan Speed
When the liquid pressure reaches 550 PSI, the
condenser fan will speed up, moving as much air as
possible in an attempt to reduce system pressures. The
condenser fan will operate at increased speed until the
liquid pressure reaches 450 PSI. At this point, the fan
will return to normal operating speed.
Second Stage Drop Out
If the liquid pressure reaches 620 PSI, the second
stage of cooling will be disabled for the remainder
of the current cooling call. This reduces the risk of
tripping the high pressure switch, while still allowing
cooling.
Low Ambient Control
At low ambient outdoor air temperatures, the fan motor
will cycle as a means of controlling the system's head
pressure to protect the system from evaporator coil freeze
FIGURE 40
Voltage to Pressure:
Liquid Pressure Transducer
FIGURE 41
Adjusting Liquid Temperature Values
