Mitsubishi Electric PUZ-WZ50VAA Service Manual page 12

substances even when a small amount of moisture is present.
It is necessary to remove a sufficient level of moisture using a vacuum pump (0.5 Torr or less).
Compound gauge
Valve on low-pressure side (blue) (Open)
Outdoor unit
Service port
- If the vacuum pump oil reverse into the refrigerant circuit, it may cause air conditioner malfunction. Therefore, use a
vacuum pump with a reverse-flow prevention device in order to prevent oil reverse-flow from the vacuum pump.
- Be sure to use a vacuum pump compliant with R290 that has been specially designed and tested not to be an ignition
source of itself. It is deeply better to use the recovery machine that comply with explosion-proof standards such as
ATEX and IECEx.
(13) Charging Procedures
Both liquid charging and gas charging are possible because R290 is a single refrigerant and its composition does not
change. However it is difficult to change a sufficient amount by gas charging since R290 is a low pressure refrigerant.
Therefore, R290 refrigerant should be charged by liquid charging using a cylinder with a siphon tube.
Liquid charging of refrigerant all at once from the low pressure side may cause the compressor malfunction. Accordingly,
make sure that charging is gradual.
< Cylinder with a siphon tube >
Cylinder
Confirm the refrigerant name on the cylinder and conduct charging with the refrigerant specified for the air conditioner.
Using the wrong refrigerant may cause mechanical problems, malfunctions and faults, or seriously endanger safety. Be
sure to conduct charging the correct refrigerant.
In addition to conventional charging procedures, the following requirements shall be followed:
• Ensure that contamination of different refrigerants does not occur when using charging equipment. Hoses or lines
shall be as short as possible to minimize the amount of refrigerant contained in them.
• Cylinders shall be kept upright.
• Ensure that the refrigeration system is earthed prior to charging the system with refrigerant.
• Label the system when charging is complete (if not already).
• Extreme care shall be taken not to overfill the refrigeration system.
Prior to recharging the system, it shall be pressure-tested with the appropriate purging gas. The system shall be leak
tested on completion of charging but prior to commissioning. A follow up leak test shall be carried out prior to leaving the
site.
(14) Decommissioning
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 refrigerant 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.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure, ensure that:
OCH816
Gauge manifold
Valve on high-pressure side (red) (Closed)
Lo HI
Blue
Yellow
Bourdon tube vacuum gauge
VAC
Reverse-flow prevention valve
Vacuum pump
Valve
Liquid
12
VAC valve
In order to prevent the vacuum pump oil reverse-flow,
use a vacuum pump with reverse-flow prevention valve.
Continued to the next page.