Chapter 6 System O&M; Operation And Maintenance Of Indoor Unit; Self-Diagnosing Functions; Electric Control Part - Liebert DM User Manual

50 Chapter 6 System O&M
This chapter introduces the operation and maintenance of the Liebert_DM 16kW air conditioner.

6.1 Operation and maintenance of indoor unit

6.1.1 Self-diagnosing Functions

As limited by the environmental conditions, certain components may remain idle for a long time, and there is no telling
of whether they are faulty. However, upon urgent needs, such components may fail to meet the demand. Therefore it
is necessary to check the system components regularly. The controller provides the function that enables you to turn
on/off the components onsite manually so as to check their functionality. For the operation instruction, see
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Note
1. During the operation of the Liebert_DM 16kW system, lethal voltage may be present in the internal parts. It is a must to obey
all the notes and warnings marked on the equipment or contained in this manual, otherwise injury or fatality may occur.
2. Only qualified maintenance and repairing personnel can operate and process the system.

6.1.2 Electric Control Part

Maintenance of electric part
Carry out visual inspection and handling over the electrical connection by referring to the following items.
1. Overall electrical insulation test: find out the unqualified contacts and handle them. Note to disconnect the fuses or
MCBs of the control part during the test lest the high voltage should damage the control components.
2. Carry out detection over the contactors before the power-on, make sure the contactors can act freely without
obstruction.
3. Clean the electric and control components 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 electric connection terminals.
6. Check that the sockets and plugs are in good condition. Replace those loosened ones.
Maintenance of control system
Carry out visual inspection, simple function test and handling over the control parts by referring to the following items.
1. Visually inspect the power transformers and isolation transformers and test the output voltage (of the indoor unit &
outdoor condensers).
2. Check that there is no signs of aging on the control interface board, display control board, sensor board and fuse
board.
3. Clean the electric control components 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 display 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, 77, 78) and the control interface board.
6. Check the output connection between the control interface board and various components, including various
contactors, solenoid valves for liquid pipes and bypass solenoid valves (HG bypass, liquid bypass). The input
connection between control interface board and various components, including fan overload protector, HP/LP
switches, heating over-temperature protection switch, humidifier dry-burn protection switch, filter clogging switch and
filter pressure difference switch. In particular, check the connection parts such as HP/LP switches and solenoid valves,
and replace the component if it is found loosened or in poor connection.
7. Replace the electric components that are detected faulty, such as faulty control fuses (or MCBs) and control boards.
Chapter 6 System O&M
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DM Series 16kW Air Conditioner User Manual
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