Mitsubishi Electric PUZ-WZ50VAA Service Manual page 7

[3] Cautions for service
(1) After completing service, charge the cycle with specified amount of refrigerant.
(2) When performing service, install a filter drier simultaneously.
Be sure to use a filter drier for new refrigerant.
[4] Safety requirement and work procedure of the repair service for unit using R290 refrigerant.
Observe the following safety requirements, precautions, and work procedures to perform the repair services.
(1) Safety check before the repair services
For repair to the refrigerating systems, (1-1) to (1-7) shall be completed prior to conducting work on the systems.
(1-1) Checks on the Area
Prior to beginning work on systems containing flammable refrigerants, safety checks are necessary to ensure that the
risk of ignition is minimized.
(1-2) Work Procedure and Tools
Work shall be undertaken under a controlled procedure so as to minimize the risk of a flammable gas or vapor being
present while the work is being performed.
Be sure to check this service manual before carrying out any work. In particular, the safety requirements, precautions
and work procedures described in Section 2 "SAFETY PRECAUTION" and Section 11 "DISASSEMBLY PROCEDURE"
must be followed.
Make sure that the tools and equipment used are approved for R290 refrigerant. Be sure to check the section "2.2.[5]
Service tools" of this service manual.
(1-3) General Work Area
All maintenance staff and others working in the local area shall be instructed on the nature of work being carried out.
Work in confined spaces shall be avoided. The area around the workspace shall be sectioned off. Ensure that the con-
ditions within the area have been made safe by control of flammable material.
(1-4) Checking for Presence of Refrigerant
The area shall be checked with an appropriate refrigerant detector prior to and during work, to ensure the technician is
aware of potentially toxic or flammable atmospheres. Ensure that the leak detection equipment being used is suitable
for use with all applicable refrigerants, i.e. non-sparking, adequately sealed or intrinsically safe.
Check if R290 refrigerant leak to the secondary circuit (heating/cooling circuit) when refrigerant leaks occur.
In the event of refrigerant leakage, to do as follows:
- Evacuate any people from the danger zone.
- From a safe position, switch off the electricity supply for all system components.
- Remove ignition sources from the danger zone.
- Do not operate the unit until repairs are completed.
(1-5) Presence of Fire Extinguisher
If any hot work is to be conducted on the refrigeration equipment or any associated parts, appropriate fire extinguishing
equipment shall be available to hand.
Have a dry powder or CO2 fire extinguisher adjacent to the charging area.
(1-6) No Ignition Sources
No person carrying out work in relation to a refrigeration system which involves exposing any pipe work shall use any
sources of ignition in such a manner that it may lead to the risk of fire or explosion. All possible ignition sources, includ-
ing cigarette smoking, should be kept sufficiently far away from the site of installation, repairing, removing and disposal,
during which refrigerant can possibly be released to the surrounding space. Prior to work taking place, the area around
the equipment is to be surveyed to make sure that there are no flammable hazards or ignition risks. "No Smoking"
signs shall be displayed.
The following are the ignition source in R290.
Source of ignition
Flame
Electric arc
Hot surface (R290 : 370 °C, R32 : 548 °C)
Electrical switch contacts (pressostats, relay, etc.)
Discharge of capacitors
Electrical potential differences
Mechanical impact of friction sparks (by tools)
Static charge on non-earthed components
(e.g. refrigerant hose)
Static charge of work clothes
Use of electric devices (smartphone, notebook, tablet)
In particular, pay attention to the following points to eliminate ignition sources.
• Sparks due to tool friction also be a source of ignition. Work that sparks should be done away from the unit.
• Be sure to use the electrical tools compliant with R290.
• Do not install unit during turning on electricity. Turn off electricity and check by tester before installing R290 unit.
• Static electricity is also an ignition source.
Anti-static measures (anti-static and static electricity elimination) should be taken.
• Do not brazing the pipe and unit which contain refrigerant. Before brazing, refrigerant must be removed.
• When repairing the refrigerant parts, remove parts to be replaced by cutting with pipe cutter, NOT by flame nor by
electric saw, etc.
OCH816
Refrigerant Security class
R290/R32 A3/A2L
R290 A3
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