Trane Modular 20 to 35 Tons Installationshandbuch PDF herunterladen (Seite 23)

Maintenance

CXRC-SVX01F-EN 23

discharge line access port). Add refrigerant to reach

pressure of 12 to 15 psig.

4. Disconnect refrigerant cylinder. Connect dry nitrogen

cylinder to high side charging port and increase

pressure to 150 psig. Do not exceed high side

(discharge) unit nameplate design pressure. Do not

subject low side (suction) components to high side

pressure.

5. Check all piping joints, valves, etc. for leaks.

Recommend using electronic detector capable of

measuring 0.1 oz/year leak rate.

6. If a leak is located, use proper procedures to remove

the refrigerant/nitrogen mixture, break connections

and make repairs. Retest for leaks.

Make sure all service valves are open.

System Repair

1. If system is water cooled with service valves, or air

cooled, high and low side may be tested independently

by closing liquid line angle valve and water cooled unit

discharge line ball valve. Otherwise leave all valves

open and DO NOT exceed low side design pressure.

2. Connect R-410A refrigerant cylinder to charging port,

add refrigerant to reach pressure of 12 to 15 psig.

3. Disconnect refrigerant cylinder. Connect dry nitrogen

cylinder to high side charging port and increase

pressure to 150 psig. DO NOT exceed unit nameplate

design pressures. If testing complete system, low side

design pressure is maximum.

4. Check piping and/or components as appropriate for

leaks.

5. Recommend using electronic detector capable of

measuring 0.1 oz/year leak rate.

6. If a leak is located, use proper procedures to remove

the refrigerant/nitrogen mixture, break connections

and make repairs. Retest for leaks.

Make sure all service valves are open.

System Evacuation Procedures

Each refrigeration circuit must be evacuated before the

unit can be charged and started.

Use a rotary type vacuum pump capable of pulling a

vacuum of 100 microns or less.

Verify that the unit disconnect switch and the system

control circuit switches are “OFF”.

Oil in the vacuum pump should be changed each time the

pump is used with high quality vacuum pump oil. Before

using any oil, check the oil container for discoloration

which usually indicates moisture in the oil and/or water

droplets. Moisture in the oil adds to what must be removed

from the system, increasing pump down time.

When connecting the vacuum pump to a refrigeration

system, it is important to manifold the vacuum pump to

both the high and low side of the system (liquid line access

valve and suction line access valve). Follow the pump

manufacturer’s directions for the proper methods of using

the vacuum pump.

The lines used to connect the pump to the system should

be copper and of the largest diameter that can practically

be used. Using larger line sizes with minimum flow

resistance can significantly reduce evacuation time.

Important: Rubber or synthetic hoses are not

recommended for system evacuation

because they have moisture absorbing

characteristics which result in excessi ve

rates of evaporation, causing pressure rise

during the standing vacuum test.This

makes it impossible to determine if the

system has a leak, excessive residual

moisture, or a continual or high rate of

pressure increase due to the hoses.

An electronic micron vacuum gauge should be installed in

the common line ahead of the vacuum pump shutoff valve,

as shown in Figure 18, p. 24. Close Valves B and C, and

open Valve A.

Start the vacuum pump, after several minutes, the gauge

reading will indicate the maximum vacuum the pump is

capable of pulling. Rotary pumps should produce

vacuums of 100 microns or less.

OpenValves B and C. Evacuate the system to a pressure of

300 microns or less. As the vacuum is being pulled on the

system, there could be a time when it would appear that no

further vacuum is being obtained, yet, the pressure is high.

It is recommended that during the evacuation process, the

vacuum be “Broken”, to facilitate the evacuation process.

To break the vacuum:

Shutoff valves A, B, & C and connect a refrigerant cylinder

to the charging port on the manifold. Purge the air from the

hose. Raise the standing vacuum pressure in the system to

“zero” (0 psig) gauge pressure. Repeat this process two or

three times during evacuation.

Note: It is unlawful to release refrigerant into the

atmosphere. When service procedures require

working with refrigerants, the service technician

must comply with all Federal, State, and local laws.

Standing Vacuum Test

Once 300 microns or less is obtained, close Valve A and

leave valves B and C open.This will allow the vacuum

gauge to read the actual system pressure. Let the system

equalize for approximately 15 minutes.This is referred to

as a “standing vacuum test” where, time versus pressure

NOTICE:

Motor Winding Damage!

Do not use a megohm meter or apply voltage to a

compressor motor winding while it is under a vacuum.

Voltage sparkover could cause damage to the motor

windings.

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