Mitsubishi Electric PUHY-M200YNW-A1 Service Handbook page 18

[1-2 Handling and Characteristics of Piping Materials, Refrigerant, and Refrigerant Oil ]
7) Ventilated area
Ensure that the area is in the open or that it is adequately ventilated before replacing parts or conducting any hot work. A
degree of ventilation shall continue during the period that the work is carried out. The ventilation should safely disperse any
released refrigerant and preferably expel it externally into the atmosphere.
8) Checks to the refrigeration equipment
Where electrical components are being changed, they shall be fit for the purpose and to the correct specification. At all times
the MITSUBISHI ELECTRIC's Installation Manual and Service Handbook shall be followed. If in doubt, consult the dealer's
technical department for assistance.
The following checks shall be applied to installations using slightly flammable refrigerants:
the amount of refrigerant charge depends on the size of the area in which products containing refrigerant are to be installed;
the ventilation machinery and outlets are operating adequately and are not obstructed;
if an indirect refrigerating circuit is being used, the secondary circuit shall be checked for the presence of refrigerant;
marking to the equipment continues to be visible and legible. Markings and signs that are illegible shall be corrected;
refrigeration pipe or components are installed in a position where they are unlikely to be exposed to any substance which may
corrode components containing refrigerant, unless the components are constructed of materials which are inherently resistant
to being corroded or are suitably protected being so corroded.
9) Checks to electrical devices
Repair and maintenance to electrical components shall include initial safety checks and component inspection procedures. If
a fault exists that could compromise safety, then no electrical supply shall be connected to the circuit until it is satisfactorily
dealt with. If the fault cannot be corrected immediately but it is necessary to continue operation, an adequate temporary so-
lution shall be used. This shall be reported to the owner of the equipment so all parties are advised.
10) Initial safety checks shall include:
that capacitors are discharged: this shall be done in a safe manner to avoid possibility of sparking;
that no live electrical components and wiring are exposed while charging, recovering or purging the system;
that there is continuity of earth bonding.
5. Repairing sealed components
1) During repairs to sealed components, all electrical supplies shall be disconnected from the equipment being worked upon prior
to any removal of sealed covers, etc. If it is absolutely necessary to have an electrical supply to equipment during servicing,
then a permanently operating form of leak detection shall be located at the most critical point to warn of a potentially hazardous
situation.
2) Particular attention shall be paid to the following to ensure that by working on electrical components, the casing is not altered
in such a way that the level of protection is affected. This shall include damage to cables, excessive number of connections,
terminals not made to original specification, damage to seals, incorrect fitting of glands, etc.
3) Ensure that the apparatus is mounted securely.
4) Ensure that seals or sealing materials have not degraded to the point that they no longer serve the purpose of preventing the
ingress of flammable atmospheres. Replacement parts shall be in accordance with the MITSUBISHI ELECTRIC's specifica-
tions.
5) The use of silicon sealant can inhibit the effectiveness of some types of leak detection equipment. Intrinsically safe compo-
nents do not have to be isolated prior to working on them.
6. Refrigerant leakage detection
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 slightly flammable refrigerants, the sensi-
tivity 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.
2) If a leak is suspected, all naked flames shall be removed/extinguished.
3) 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. Because R32 is slightly flammable, oxygen free
nitrogen (OFN) shall be poured through the system both before and during the brazing process to purge R32.
BS_01_G
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