Vertiv | Liebert® PEX3™ Series Precision Air Conditioner | User Manual 94
System Operation and Maintenance
3. Clean the electric and control elements of dust with brush or dry compressed air.
4. Check the closing of contactors for arcs or signs of burning. Replace the contactor if necessary.
5. Fasten all the electrical connection terminals.
6. Check whether the sockets and plugs are in good conditions. Replace those damaged ones.
7. If the power cables are damaged, to avoid further damage, the cables must be replaced by professional
personnel.
6.5. Appearance Inspection and Maintenance of Controller
Components
A control section to make visual inspection of the following entries, and a simple function test process:
1. Visually inspect the power transformers and isolation transformers and test the output voltage of the indoor
unit and outdoor unit.
2. Check whether there are no signs of aging on the control interface board, control board, temperature and
humidity sensor board.
3. Clean the electrical control elements and control board of dust and dirt with brush and electronic dust
removing agent.
4. Check and fasten the I/O ports at the control interface board, including the connection between control
board and control interface board, as well as between the temperature/humidity sensor board and the
interface board.
5. Check the connection between the user terminals (70#, 71#, 70A#, 71A#, 37#, 38#) and the control interface
board.
6. Check the output connection between the control interface board and various contactors and solenoid
valves for liquid pipes, and the input connection between control interface board and fan overload protector,
high pressure switch, heating over-temperature protection switch, humidier protection switches, discharge
air temperature sensor, and low-pressure sensor. In particular, check the connection parts such as high-
pressure switches and solenoid valves, and replace the component if it is in poor condition or is faulty.
7. Check and replace electrical components that are faulty, such as control fuses (or MCBs) and control boards.
8. Check the specication and aging condition of the control cable and power cable between the indoor unit
and the outdoor unit and replace the cables if necessary.
9. Use temperature and humidity measuring meters with higher precision to measure and calibrate the
temperature and humidity sensors.
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