Dehumidification; Electronic Expansion Valve (Eev); Eev Components; Electronic Expansion Valve - Bard FUSION-TEC HR36APA Service Instructions Manual

Dehumidification

The unit uses a dehumidification sequence that does
not require the electric heat to run at the same time
as the compressor. Instead, the unit will turn on the
compressor to cool down to the heating setpoint.
Once the lower setpoint has been reached, the unit
will heat the space back up to the upper setpoint.
This cycle continues until the humidity level in the
shelter reaches an acceptable level. At this point,
the unit will revert back to normal operation. The
economizer will also be disabled while the unit is in
the dehumidification mode.
NOTE: This feature is dependent upon the LV1000
indoor humidity sensors and a command
from the LV to enter dehumidification mode.
See the latest revision of LV1000 Service
Instructions 2100-673 for adjustment of the
dehumidification setpoint and differentials.

Electronic Expansion Valve (EEV)

EEV Components

Electronic Expansion Valve

The electronic expansion valve is a stepper motor that
is controlled with a step output from the controller. The
valve is capable of 480 steps represented by a 0-100%
signal on the controller. The motor drives a needle valve
that regulates the flow of refrigerant.

Suction Pressure Transducer

The unit has a pressure transducer installed on
the suction line between the evaporator coil and
compressor. The transducer is used for system
monitoring of suction system pressures. The sensor is
used with the suction temperature sensor to provide
a real time superheat calculation that determines the
EEV position.
This 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 Suction Pr
Sensor (C11); press ENTER key.
5. Verify the measurement displayed on screen is
accurate (see Figure 11).
6. If the measurement needs to be adjusted, apply an
offset value by pressing ENTER to scroll to Offset.
7. Press UP or DOWN keys to adjust the offset.
8. The update will not take effect until the cursor is
moved out of the Offset parameter.
9. Once adjusted, press the ESCAPE key several
times to return to Main Menu screen.
Manual 2100-670B
Page 12 of 33
FIGURE 11
Adjusting Suction Sensor/Transducer
Pressure Values

Troubleshooting the Suction Pressure Transducer

0-250 psig
-5v Nominal .5 – 4.5v Actual
4v/250 psig = .016 volts per 1 psig
Example: 125 psig x .016 + .5 volts = 2.5 volts
Formula for Tech:
Measured Pressure x .016 + Sensor Offset = Expected
Transducer Signal Voltage (see Figure 12).
FIGURE 12
Voltage to Pressure: Suction Pressure Transducer

Suction Pressure Alarm

When the suction pressure transducer value is out
of range (0-250 PSIG), the controller will generate
a sensor failure alarm to indicate the sensor is not
working properly.
This alarm cannot be adjusted.
Alarm index numbers: 141, 142, 143, 144

Suction Temperature Sensor

The suction temperature sensor is used to calculate
superheat. The EEV uses this value to control the EEV.
The temperature is measured with a 10k ohm NTC
thermistor.
The suction temperature sensor measurement can be
verified and adjusted by:
1. Press MENU key to go to the Main Menu screen.