R134a Field-Charging Procedure

Maintenance

Some symptoms of an oil under- charged unit:

•Compressor rattle or grinding sound

•Lower-than-normal pressure drop through oil system

•Seized or Welded Compressors

•Low oil-sump level after normal shutdown

•Lower-than-normal oil concentrations in the evaporator

Be certain that the electrical power to the unit is disconnected before performing this procedure.

WARNING

Position all electrical disconnects in the "Open" position and lock them to prevent injury or death due to electrocution. Follow this procedure when the unit is empty of all refrigerant and under a vacuum.

CAUTION

Water must be flowing through the evaporator during the entire charging process to avoid freezing and rupturing of the evaporator tubes.

1.Find the weight of the amount of charge given inTable 1.

2.Attach the charging hose to the evaporator service valve (3/8" [9 mm] flare). Open the service valve.

3.Add charge to the evaporator to bring the total circuit charge up to the level given inTable 1.

4.Close the service valve and disconnect the charging hose.

Adding charge

This procedure should be followed when adding charge to an undercharged unit. When low charge is indicated by low subcooling in the liquid line, charge should be added until sufficient subcooling is achieved.

1.Attach the charging hose to the evaporator service valve (3/8"

[9 mm] flare). Open the service valve.

2.Add 4.5 kg of refrigerant (R134a) charge.

3.Close the valve, remove the charging hose and start the unit. Monitor subcooling.

4.If subcooling is still insufficient, return to step number 2.

Note: Proper subcooling can be determined from run-log history, service experience, or by contacting Trane technical service.The service tool may include a calculation module that determines the proper subcooling for any operating condition (Trane Service only).

Charge Isolation in the high or low side of the system

All the refrigerant may be trapped into the high side (condenser) of the unit for maintenance on the compressor (or low side). With the suction-line service valve option, charge may also be isolated in the evaporator for maintenance on the compressor (or high side). It is much more preferable to isolate the charge in the evaporator, if this option is available.

High side charge isolation procedure:

1.Make sure the circuit is off.

2.Shut the liquid-line service valve.

3.Shut the oil return-line service valve.

4.Start the circuit with the service tool in charge-isolation mode:

•All fans will turn on

•EXV will open 100%

•The oil return-line solenoid will open

•The unit will start at minimum load

•The unit will run until it cuts out on low pressure (~6 psia) [0.41 bar].

5.When the unit trips, the discharge check valve and the oil-line shutoff valve close.

6.Close the discharge isolation valve.

7.Close the oil-line shutoff valve.

8.Remove the remainder of the charge with the vacuum pump. Recommendation: Do not pump the remaining charge into the high side.This may introduce non- condensable gasses and other contaminants into the unit.

9.The low side and the compressor may be serviced at this time.

Returning the unit to running condition:

1.Open all the valves.

2.Manually open EXV for 15 minutes to allow the refrigerant to drain to the evaporator by gravity.

3.Let the unit sit with heaters on to drive refrigerant out of the oil and warm up the compressor bearings. Depending upon ambient conditions, this may take up to 24 hours.

4.After the oil level has returned to normal, the unit can be put back into operation.

Low-side charge-isolation procedure: After normal shutdown, most of the charge resides in the evaporator. Running cold water through the evaporator may also drive much of the refrigerant to the evaporator.

1.Make sure the circuit is off.

2.Close the suction-line isolation valve.

3.Close the oil return-line service valve.

4.Close the liquid line service valve.

5.Manually open the EXV.

6.Use a liquid pump or vacuum pump to move refrigerant from the condenser to the evaporator.

The liquid pump will only be effective if there is a lot of charge in the condenser. It may be connected to the condenser drain port on the liquid-line isolation valve.

Note: if a pump is to be used, connect it before closing this valve. This port is only isolated when the valve is backseated. If a vacuum pump is used, then connect it to the discharge-line service valve near the oil separator. A vacuum pump will be required for part of the procedure.

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