DC Inverter U-match Series Duct Type Unit
63
(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.
The refrigerant charge shall be recovered into the correct recovery cylinders.
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
pipework are to take place.
Ensure that the outlet for the vacuum pump is not close to any ignition
sources and there is ventilation available.
5.4.7 Charging Procedures
In addition to conventional charging procedures, the following requirements
shall be followed.
(1) 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.
(2) Cylinders shall be kept upright.
(3) Ensure that the refrigeration system is earthed prior to charging the system
with refrigerant.
(4) Label the system when charging is complete (if not already).
(5) Extreme care shall be taken not to overfill the refrigeration system.
(6) 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.
