Carrier 69NT40-511-199, 69NT40-521 manual Evacuation and Dehydration, Refrigerant Charge

d.Evacuate and dehydrate the unit. (Refer to section 6.5.)

e.Charge unit per section 6.6.

6.5 EVACUATION AND DEHYDRATION

6.5.1General

Moisture is the deadly enemy of refrigeration systems. The presence of moisture in a refrigeration system can have many undesirable effects. The most common are copper plating, acid sludge formation, “freezing-up” of metering devices by free water, and formation of acids, resulting in metal corrosion.

6.5.2Preparation

a.Evacuate and dehydrate only after pressure leak test. (Refer to section 6.4.)

b.Essential tools to properly evacuate and dehydrate any system include a vacuum pump (8 m3/hr = 5 cfm volume displacement, P/N 07-00176-01) and electronic vacuum gauge.

c.If possible, keep the ambient temperature above 15.6_C (60_F) to speed evaporation of moisture. If the ambient temperature is lower than 15.6_C (60_F), ice might form before moisture removal is complete. Heat lamps or alternate sources of heat may be used to raise the system temperature.

d.Replace the filter-drier with a section of copper tubing with the appropriate fittings. This action will help speed the evacuation procedure.

6.5.3Procedure

a.Remove all refrigerant using a refrigerant recovery system.

b.The recommended method to evacuate and dehydrate the system is to connect three evacuation hoses, as shown in Figure 6-4, to the vacuum pump and refrigeration unit. DO NOT use standard service hoses, as they are not suited for evacuation purposes. Also as shown, connect a evacuation manifold, with evacuation hoses only, to the vacuum pump, electronic vacuum gauge, and refrigerant recovery system.

c.With the unit service valves closed (back seated) and the vacuum pump and electronic vacuum gauge valves open, start the pump and draw a deep vacuum. Shut off the pump and check to see if the vacuum holds. This operation is to test the evacuation setup for leaks. Repair if necessary.

d.Midseat the refrigerant system service valves.

e.Open the vacuum pump and electronic vacuum gauge valves, if they are not already open. Start the vacuum pump. Evacuate unit until the electronic vacuum gauge indicates 2000 microns. Close the electronic vacuum gauge and vacuum pump valves. Shut off the vacuum pump. Wait a few minutes to be sure the vacuum holds.

f.Break the vacuum with clean dry refrigerant gas. Use refrigerant specified for the unit. Raise system pressure to approximately 2 psig, monitoring it with the compound gauge.

g.Remove refrigerant using a refrigerant recovery system.

h.Repeat steps (e) through (g) one time.

i.Remove the copper tubing and change the filter-drier. Evacuate unit to 500 microns. Close the electronic vacuum gauge and vacuum pump valves. Shut off the vacuum pump. Wait five minutes to see if vacuum holds. This procedure checks for residual moisture and/or leaks.

j.With a vacuum still in the unit, the refrigerant charge may be drawn into the system from a refrigerant container on weight scales. The correct amount of refrigerant may be added by observing the scales. (Refer to section 6.6)

6.6 REFRIGERANT CHARGE

6.6.1Checking the Refrigerant Charge

NOTE

To avoid damage to the earth’s ozone layer, use a refrigerant recovery system whenever removing refrigerant. When working with refrigerants you must comply with all local government environmental laws. In the U.S.A., refer to EPA section 608.

NOTES

SSet the controller set point to -25_C (-13_F) to ensure that the suction modulation valve is fully open when checking operation of unit.

SThe refrigerant level should only be checked when the unit is running with the suction modulation valve fully open. The container temperature should be approximately 1.7_C (35_F) or -17.8_C (0_F).

a.Connect the gauge manifold to the compressor discharge and suction service valves.

SECTION 6

6-5 T-268-07