Midea MPPB-14CRN7 Manuel D'utilisation page 51

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may need re-calibration. (Detection equipment shall be
calibrated in a refrigerant-free area.) Ensure that the
detector is not a potential source of ignition and is suitable
for the refrigerant used. Leak detection equipment shall be
set at a percentage of the LFL of the refrigerant and shall be
calibrated to the refrigerant employed and the appropriate
percentage of gas (25 % maximum) is confirmed. Leak
detection fluids are suitable for use with most refrigerants
but the use of detergents containing chlorine shall be
avoided as the chlorine may react with the refrigerant and
corrode the copper pipe-work. If a leak is suspected, all
naked flames shall be removed/ extinguished. If a leakage
of refrigerant is found which requires brazing, all 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.
12.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 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 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.
13.Charging procedures
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 minimise the amount of
refrigerant contained in them.
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EN