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of the refrigerant shall be recovered from the system, or isolated (by means
of shut off valves) in a part of the system remote from the leak. Oxygen free
nitrogen (OFN) shall then be purged through the system both before and
during the brazing process.
11.Removal and evacuation
When breaking into the refrigerant circuit to make repairs or for any other
purpose conventional procedures shall be used. However, it is important
that best practice is followed since flammability is a consideration. The
following procedure shall be adhered to:
Remove refrigerant; Purge the circuit with inert gas; Evacuate; Purge again
with inert gas; Open the circuit by cutting or brazing.
The refrigerant charge shall be recovered into the correct recovery cylin-
ders. 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 this task. 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.
Ensure that the outlet for the vacuum pump is not close to any ignition
sources and there is ventilation available.
12.Charging procedures
In addition to conventional charging procedures, the following require-
ments 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 minimise 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 OFN. 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.
13.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
Inverter Window Air Conditioner
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