Mitsubishi SRK20ZSX-W Technical Manual page 154

►Cabling
(1) Check that cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp edges or any other adverse
environmental effects. The check shall also take into account the effects of aging or continual vibration from sources such
as compressors or fans.
►Detection of flammable refrigerants
Under no circumstances shall potential sources of ignition be used in the searching for or detection of refrigerant leaks. A halide
torch (or any other detector using a naked flame) shall not be used.
►Leak detection methods
The following leak detection methods are deemed acceptable for all refrigerant systems.
(1) Electronic leak detectors may be used to detect refrigerant leaks but, in the case of flammable refrigerants, the sensitivity
may not be adequate, or 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.
(2) Leak detection fluids are suitable for use with most refrigerants but the use of detergents containing chlorine shall be avoid-
ed as the chlorine may react with the refrigerant and corrode the copper pipe-work.
(3) If a leak is suspected, all naked flames shall be removed/extinguished.
(4) If a leakage of refrigerant is found which requires brazing, all of the refrigerant shall be recovered from the system, or iso-
lated (by means of shut off valves) in a part of the system remote from the leak.
For appliances containing flammable refrigerants, oxygen free nitrogen (OFN) shall then be purged through the system
both before and during the brazing process.
►Removal and evacuation
When breaking into the refrigerant circuit to make repairs – or for any other purpose – conventional procedures shall be used.
However, for flammable refrigerants 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.
For appliances containing 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.
For appliances containing flammable refrigerants, 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 that ventilation is available.
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'18 • SRK-T-234