Vertiv | Liebert® DM | User Manual 41
Mechanical Installation
2.8. Charging Refrigerant
• Leak Test and System Vacuuming
1. Open the Thermal expansion valves for evacuation then connect refrigerant gauges to the suction valves and to the
discharge line of Schrader valves.
2. Open the service valves and place a 150 psig (1034 kPa) of dry Nitrogen with a tracer of refrigerant. After that check
system for leaks with a suitable leak detector.
3. After four hours, check the pressure readings and, if they have not changed, break vacuum with dry Nitrogen, and
vacuum the system second and third time with 250 microns or less. Recheck the pressure after two hours.
• For the downflow unit, a tube with a Schrader valve is extended from the compressor suction line to the
side of the unit for ease of service access. Refer Figure 2-18 to Figure 2-22.
• If the unit is equipped with an optional low temperature kit, the nitrogen in the liquid storage tank should be
released before the unit is vacuumed.
2.8.1. Base Charging of Refrigerant
After vacuum inspection, immediately charge the cooling system with proper amount of liquid refrigerant (generally charge
until the pressure in the tank is balanced with the system pressure).
1. Connect the high and low composite pressure gauge to the refrigerant cylinder, and ensure that the connection hose is
vacuumed.
2. Connect the high and low pressure composite pressure gauge to the Schrader valve interfaces at the liquid pipe angle
valve and the compressor suction pipe Schrader valve interface, and keep the refrigerant cylinder
up-side-down during the static charging process.
3. When the amount of the refrigerant reaches the calculated charging amount, the static charging should be stopped.
4. Do not turn on the unit immediately after static charging.
5. Prior to turning on the unit, ensure to preheat the compressor crankcase by heating belt for more than 12hours, if the
preheating time is insuicient, use an air drier or other safe heating source to heat the housing of the compressor for
about 30minutes so as to evaporate any liquid refrigerant.
The recommended standard refrigerant amount (kg) of the unit is shown in Table 2-11.
Table 2-11 Recommended Base Refrigerant Charge Quantity (R410A)
Unit Model
DME07
(Upflow)
+DMC07
DME12
(Upflow)
+DMC12
DME17
(Upflow)
+DMC17
DME22
(Upflow)
+DMC22
DME22
(Downflow)
+DMC22
DME27
(Upflow)
+DMC27
DME27
(Downflow)
+DMC27
Base charge
(kg) -
Standard
pipe length
within 10 m
2.5 3.2 5.2 8.1 7.5 9.4 9.0
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