Webasto BCT010300C Repair Manual download pdf (Page 39)

Compressor Replacement and System Service

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1. Evacuate the system to 29 inches vacuum. Break

vacuum with refrigerant to be used for final charging

of system and vapor charge to 35-50 pounds gauge

pressure. Leave vapor charge in system for a

minimum of five minutes. Reduce pressure to 0

gauge pressure.

2. Repeat step 1.

3. Evacuate system to 29 inches vacuum. Charge

system with the specified kind and quantity of

refrigerant.

Never use a compressor to evacuate a

system. Instead, use a high vacuum

pump specifically designed for that

purpose.

Never start the compressor while it is under deep

vacuum. Always break a vacuum with refrigerant charge

before energizing the compressor.

Failure to follow these instructions can damage the

hermetic terminal and may result in terminal venting. As

always, to reduce the risk of serious injury or death from

fire due to terminal venting, never energize the

compressor unless the protective terminal cover is

securely fastened.

D. Charge the System and Check the Pressure

Drop

Charge the system and place in operation. Follow the

safety precautions outlined in “System Charging” on

page 29. Immediately after startup, check the pressure

drop across the suction line filter-drier. This will serve

two purposes:

• Verify that the drier selection was correct; that is,

large enough.

• Serve as a base point to which subsequent

pressure checks can be compared.

Because the permissible pressure drop across the drier is

relatively small, it is suggested that a differential pressure

gauge be used for the measurement.

E. Measure the Pressure Drop

After the system has been operating for an hour or so,

measure the pressure drop across the suction line filter-

drier.

In the case of Compressor Housing Contamination, little

change should be noted. The pressure drop will, in most

instances, be below that tolerable for a permanent

installation as described in “Install Replacement

Compressor and Components” on page 36.

On the other hand, where Systems Contamination

occurred, an increased pressure drop will be measured.

Change the suction filter-drier and the liquid line filter-

drier whenever the pressure drop approached or exceeds

9 psi allowed for temporary operation during cleanup.

Keep changing both the suction and liquid line filter-

driers until the pressure drop stabilizes at or below 2 psi

for permanent operations in a system (see “Install

Replacement Compressor and Components” on

page 36). At this point, it is the service person’s option as

to whether to leave the suction drier in the system or

remove it from operation.

If the system is to be opened to permit the permanent

removal of the suction filter-drier then the liquid line

filter-drier should be changed once more.

F. Test for Acidity if Multiple Motor Failures

Have Occurred

If the system has suffered multiple motor failures, it is

advisable that the oil of the replacement be tested after

Section E and judged acid free before the system is

considered satisfactorily cleaned.

An oil sample may be taken from a hermetic system if at

the time the replacement compressor was installed an oil

trap is installed in the suction line (see Fig. XXX).

When the trapped oil level appears in the sight glass (less

than an ounce is needed) the oil may be slowly

transferred to the beaker of the acid test kit as available

from several manufacturers. A reading of less that 0.05

acid number is an indication that the system is free of

acid. A reading of higher than 0.05 means continued

cleaning is required. Return to B2 on page 36.

G. Monitor the System

The above procedure for the cleanup of hermetic systems

after motor failure through the use of suction line filter-

drier will prove satisfactory in most instances provided

the system is monitored and kept clean by repeated drier

changes, if such are needed. The failure to follow these

minimum cleanup recommendations will result in an

excessive risk of repeat motor failure.

WARNING

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Webasto BCT010300C Repair Manual Page 39

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