Mitsubishi Electric City Multi CMH-WM250V-A, Service Handbook

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[1-2 Handling and Characteristics of Piping Materials, Refrigerant, and Refrigerant Oil ]
8 -
chapter 1 BS_01_G
1
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7. Refrigerant removal and vacuum drying for service
1) R32 is slightly flammable. Follow the procedures below to reduce the risk of R32 from catching fire:
1. Remove refrigerant;
2. Purge the circuit with inert gas;
3. Evacuate;
4. Purge again with inert gas;
5. Open the circuit by cutting or brazing.
2) The charged refrigerant shall be recovered into the recovery cylinders designated for use with R32. For appliances containing
slightly flammable refrigerants, the system shall be "flushed" with OFN to render the unit safe. This process may need to be
repeated several times. Compressed air or oxygen shall not be used for purging refrigerant systems.
3) Because R32 is slightly flammable, flushing shall be achieved by breaking the vacuum in the system with OFN and continuing
to fill until the working pressure is achieved, then venting to atmosphere, and finally pulling down to a vacuum. This process
shall be repeated until no refrigerant is within the system. When the final OFN charge is used, the system shall be vented
down to atmospheric pressure to enable work to take place. This operation is absolutely vital if brazing operations on the pipe-
work are to take place.
4) Ensure that the outlet for the vacuum pump is not close to any ignition sources and that ventilation is available.
8. Decommissioning
1) Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all its detail.
It is recommended good practice that all refrigerants are recovered safely. Prior to the task being carried out, an oil and re-
frigerant sample shall be taken in case analysis is required prior to re-use of reclaimed refrigerant. It is essential that electrical
power is available before the task is commenced.
2) Become familiar with the equipment and its operation.
3) Isolate system electrically.
4) Before attempting the procedure, ensure that:

mechanical handling equipment is available, if required, for handling refrigerant cylinders;

all personal protective equipment is available and being used correctly;

the recovery process is supervised at all times by a competent person;

recovery equipment and cylinders conform to the appropriate standards.
5) Pump down refrigerant system, if possible.
6) Make sure that cylinder is situated on the scales before recovery takes place.
7) Start the recovery machine and operate in accordance with MITSUBISHI ELECTRIC's instructions.
8) Do not overfill cylinders. (No more than 80% volume liquid charge)
9) Do not exceed the maximum working pressure of the cylinder, even temporarily.
10) When the cylinders have been filled correctly and the process completed, make sure that the cylinders and the equipment
are removed from site promptly and all isolation valves on the equipment are closed off.
11) Recovered refrigerant shall not be charged into another refrigeration system unless it has been cleaned and checked.
9. Labelling
1) Equipment shall be labelled stating that it has been de-commissioned and emptied of refrigerant. The label shall be dated and
signed. Because R32 is slightly flammable, ensure that there are labels on the equipment stating the equipment contains flam-
mable refrigerant.
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