System Pressures; Suction Pressure Transducer; Troubleshooting The Suction Pressure Transducer; Suction Pressure Alarm - Bard MEGA-TEC W180B Service Instructions Manual

System Pressures

To view system pressure and temperatures during this
process:
1. From the Status screen, press UP or DOWN key
until Quick Menu displays Unit Information icon
( ). Press ENTER key.
2. Press UP or DOWN keys to scroll to A/C Circuit 1
Info and A/C Circuit 2 Info screens (see Figure 8
on page 10).

Suction Pressure Transducer

The unit has pressure transducers installed on
the suction line between the evaporator coil and
compressor (one on refrigerant circuit 1 and one on
refrigerant circuit 2). The transducer is used for system
monitoring of suction system pressures. The transducer
is used with the suction temperature sensor to provide
a real time superheat calculation that determines the
EEV position.
This transducer reading 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 Analog Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Analog Ins
C3-6 (for circuit 1) or Analog Ins C3-8 (for circuit
2).
6. Verify the measurement displayed on screen is
accurate (see Figure 24).
7. If the measurement needs to be adjusted, apply an
offset value by pressing ENTER to scroll to Offset.
8. Press UP or DOWN keys to adjust the offset.
9. The update will not take effect until the cursor is
moved out of the Offset parameter.
10. Once adjusted, press the ESCAPE key several
times to return to Main Menu screen.
FIGURE 24
Adjusting Suction Sensor/Transducer
Pressure Values
Manual 2100-749
Page 18 of 68

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 + Voltage Offset = Expected
Transducer Signal Voltage (see Figure 25).
FIGURE 25
Voltage to Pressure: Suction Pressure Transducer

Suction Pressure Alarm

When the suction pressure transducer value is
measured out of range (0-250 PSIG) and the
compressor has been operating for longer than 1
minute (verified by discharge pressure transducer),
the controller will generate a sensor failure alarm to
indicate the sensor is not working properly.
This alarm cannot be adjusted.

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.
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 Analog Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Analog Ins C3-
10 (for circuit 1) or Analog Ins C3-11 (for circuit 2).
6. Verify the measurement displayed on screen is
accurate (see Figure 26).
7. If the measurement needs to be adjusted, apply an
offset value by pressing ENTER to scroll to Offset.