Liebert DM Series User Manual

Chapter 7 Troubleshooting 43
New Liebert_DM Series Air Conditioner User Manual
Chapter 7 Troubleshooting
This chapter expounds the troubleshooting of the Liebert_DM AC.
See Table 7-1 for the troubleshooting of the Liebert_DM AC.
Table 7-1 Troubleshooting
Fault phenomenon
Possible cause
Check or remedy
Unit does not start
No power to unit
Check unit input voltage
Circuit breaker that controls voltage (at
the transformer) is open
Locate short circuit and reset circuit breaker
Float switch relay has closed due to high
water level in the condensate pump sump
Check that drain pipes and pipelines are clogged or that
the condensate pump is damaged
Jumping cables not in place
Check jumping cables on the control board
No cooling
Compressor contactor not pulling in
Check for 24Vac
±
2Vac at the winding. If the voltage is
right, check the contactor
High compressor discharge pressure
See ‘High pressure alarm’ for checking and maintenance
descriptions
Plugged strainer
Clean or replace the strainer
Low refrigerant charge
Use suction and discharge pressure gauge to check the
pressure. View whether evident bubbles exits through the
sight glass
High pressure alarm
Insufficient airflow across condenser
Remove debris from coil surface and air inlet; check the
control board for the fan speed regulation performance
Condenser fan not operating
Check that the cable connection from the control board to
the terminal block of outdoor unit is tight; check that the
outdoor unit connections are tight; check that the
condensate pressure sensor works normally
Heater does not
operate
Heat function disabled in Select Options
menu
Set Heat to ‘ON’, refer to Select Options in
5.6.5 System Menu
No heat demand output from the control
system
Adjust temperature setpoint and sensitivity within the
required range
Elements burned out
Turn off the power. Check the element resistance with a
multimeter
Display abnormal
Static discharge
Disconnect the system power, and then restart
Loose connection between display board
and control board
Tighten the connection after powering off, and then
restart
No display, control
buttons do not respond
and equipment
operates normally
Disconnection between display board and
control board
Check the connection between display board and control
board
Display board fault Replace the display board
No display, control
buttons do not respond
and equipment has no
output
Low power voltage
Check for power voltage
Communication between control board
and display board interrupted
Check the connection between control board and display
board
Low pressure alarm
Refrigerant leakage
Check for leaking place and re-charge
Outdoor ambient temperature too low
Contact local maintenance engineer
Outdoor unit fan running at full speed
upon low outdoor ambient temperature
Check that the cable connections of outdoor unit are
normal; check that the condensate pressure sensor is
normal
High temperature
alarm
High temperature setpoint unreasonable
Reset the setpoint
Room load exceeding unit design ability
Check for room seal or make capacity expansion
Low temperature alarm
Low temperature setpoint unreasonable
Reset the setpoint
Heater operation current improper
Check for heater working operation
High humidity alarm
Setpoint unreasonable
Reset the setpoint
Vapor barrier not done in the room
Check for the vapor barrier
Low humidity alarm
Setpoint unreasonable
Reset the setpoint

Liebert DM Series Specifications

General

Refrigerant	R410A
Compressor Type	Scroll
Airflow	Varies by model
Power	Varies by model
Sound Pressure Level	Varies by model
Dimensions (HxWxD)	Varies by model
Weight	Varies by model