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Vertiv / Precision air conditioning

Liebert DME20 Equipment information & support

Vertiv Liebert DME20 is an industrial precision environmental control unit delivering 20kW sensible cooling with precise temperature/humidity regulation for IT rooms.

Equipment information

Brand
Vertiv
Equipment model
Liebert DME20
Equipment type
Precision air conditioning
Controller / software version
Confirm against the installed equipment
View full product specifications
Liebert DME20 Official Product View 1

Information below comes from the current product catalogue. Confirm the controller, software version and configuration of the installed equipment separately.

AC Input Voltage Range
380VAC ± 10% (3-Phase 5-Wire 50Hz) VAC
Cooling Method
Powerful circulating airflow provided by an EC variable-speed centrifugal fan
Physical Dimensions Spec
1950 × 800 × 800 mm
Operating Temperature
-15°C ~ +45°C (year-round 24×7 continuous operation)

Alarms & troubleshooting

HP_ALARM (Compressor High Pressure Alarm)
Alarm LED solid RED, buzzer sounds
Poor outdoor condenser heat dissipation or dirty/clogged fins; condenser fan speed controller failed or fan motor stalled; refrigerant overcharged; non-condensable gas in system; faulty high-pressure switch.
1. Inspect and clean outdoor condenser fins using compressed air or low-pressure water. 2. Check power supply and speed control board of the condenser fan to ensure smooth modulation based on discharge pressure. 3. Connect manifold gauges to verify discharge pressure; check for overcharge and evacuate/recharge if non-condensables exist. 4. Once pressure normalizes, manually reset the mechanical HP switch and clear the alarm on the controller.
LP_ALARM (Compressor Low Pressure Alarm)
Alarm LED blinking RED (1Hz), audible buzzer
Refrigerant leakage causing low system pressure; indoor air filter heavily clogged; expansion valve (EEV/TXV) stuck closed or bulb failed; liquid line filter drier restricted; low ambient starting without proper LP bypass.
1. Inspect indoor return air filters and evaporator coil for icing or blockage; clean or replace filters. 2. Use a halogen leak detector or soap bubble solution to inspect brazed joints, flare fittings, and Schrader valves for leaks. 3. Check moisture liquid indicator sight glass; inspect temperature differential across filter drier (replace if delta-T > 1.5°C). 4. Repair leak, perform nitrogen pressure hold, vacuum down to <500 microns, recharge according to nameplate, and reset alarm.
AIR_LOSS (Airflow Loss / Fan Fault)
Alarm LED solid RED, Run LED turns off
Indoor EC fan circuit breaker tripped; fan drive module overheated or motor winding damaged; airflow differential pressure switch tubing disconnected, kinked, or switch damaged; 0-10V speed control signal cable disconnected.
1. Verify indoor fan circuit breaker status and measure incoming voltage for balance and specification. 2. Inspect differential pressure switch (DPS) sensing tubes for disconnection or blockage; verify switch contacts with multimeter. 3. Measure the 0-10VDC analog control signal from the main board to the fan motor driver. 4. Manually spin the blower impeller to check for mechanical binding; replace the EC fan assembly if the motor winding or integrated inverter is defective.
WATER_OVF (Condensate Water Overflow Alarm)
Alarm LED solid RED, unit interlock shutdown
Condensate drain line clogged or backpressured; condensate drain pump power failure or pump impeller fouled/stuck; float level switch stuck at high position; dry condensate P-trap causing negative pressure water holding.
1. Inspect and flush the drain pan outlet and downstream drain piping to clear algae or sludge. 2. Verify electrical power to the condensate removal pump; clear debris from the pump reservoir and test check-valve. 3. Manually toggle the float level switch and verify contact continuity using a multimeter. 4. Drain the overflow pan, prime the drain trap with water to re-establish the air seal, and reset the alarm on the controller.
SENS_COMM_ERR (Return Air Temp/Humidity Sensor Fault)
Alarm LED blinking AMBER (0.5Hz), LCD shows invalid sensor readings (--)
Return air temp/humidity sensor cable loose, reversed, or suffering from shielding interference; incorrect RS-485 sensor address dip-switch setting; main board DC auxiliary power supply (+12V/+24V) failure; damaged sensing element.
1. Inspect the terminal block of the return air sensor behind the filters; tighten screws and verify RS-485 (A+/B-) polarity. 2. Measure DC voltage across sensor terminals (V+ and GND) with a multimeter to confirm steady +12V to +24VDC supply. 3. Check the DIP switch address and baud rate settings on the sensor board against Liebert controller parameters. 4. If wiring, voltage, and address settings are confirmed good but values fail to display, replace the sensor assembly.

Access Complete Maintenance & Full Alarm Troubleshooting Manual

This page lists high-frequency critical alarm codes commonly encountered in field maintenance. Comprehensive manufacturer troubleshooting matrices, board-level repair guides, detailed electrical schematics, and firmware commissioning manuals are delivered alongside equipment upon formal project procurement, accompanied by dedicated FAE technical support.

Contact Account Manager for Full Manual

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