4. “Pressure Equipment Regulations”
• Clause 17 of the pressure equipment regulation it
states that;
• “No person shall –
1. handle, store, or distribute any gas in any manner, which includes
the filling of a container.
2. install or remove a gas appliance or a gas system unless such a
person is an authorised person; or
3. After installation or re-installation, and before commissioning a gas
system, the user shall ensure that an external inspection and leak
test are performed by an authorised person or an approved
inspection authority.
4. An authorised person or an approved inspection authority shall
issue a certificate of conformity after completion of a gas
installation, modification, alteration or change of user or ownership.
A COC book may be ordered from Mr Barney @ Saracca in Johannesburg.
5. HCs (halogen free long term alternatives)
These are “halogen free long term alternatives” that include
R290 (propane) and R600a (Isobutane) and is
hydrocarbon refrigerants.
Due to its flammability the hydrocarbons are mainly used
in smaller, hermetic units with a low refrigerant charge,
such as domestic and commercial refrigerators and
freezers.
6. R290 refrigerant (propane).
Ozone depletion potential ODP = 0, global warming potential GWP = 3.3 It is characterized by low
cost and it is non-toxic. While using this refrigerant, there is no problem with selection of structural
materials for the parts of compressor, condenser and evaporator. Propane is easily resolved in mineral
oils. Boiling point under the atmospheric pressure is -42,1°C. The advantage of propane is also low
temperature at the exit out of the compressor. However, propane as a refrigerant has two
fundamental disadvantages. First, it is fire risky; second, size of the compressor should be
bigger than while using of R22 of the assigned cold-productivity in the refrigeration machine.
7. R600a refrigerant (Isobutane)
• In comparison with R12 and R134a refrigerants,
isobutane has considerable ecological advantages.
• This natural gas (ODP = 0) and (GWP = 4).
Isobutane is combustible [class B2], easily inflammable and explosive.
8. Because of the flammability of isobutane in a wide concentration
range, safety precautions are necessary on the appliance itself.
All electrical elements switching during normal operation are
taken to be possible ignition sources.
This includes thermostat, door contacts for lighting, on/off and other
switches, like defrost, compressor relays, external klixon, defrost
timers.
All refrigerant containing parts are taken to be possible
refrigerant sources through leaks.
This includes evaporators, condensers, door heaters, tubing and the
compressor.
Maximum refrigerant charge is set to be 150 g.
By keeping the charge to max. 25 % of lower explosion level (LEL),
which is approx. 8 g/m3, for a standard kitchen, ignition risk is very
low.
9. Working procedures on fridges with R600a
Read all instructions on the fridge before u start.
Connect a line tap valve on the process line.
Connect a hose thru gauges to the recovery machine inlet and connect on the
discharge of the recovery machine a 3m long hose away from your working area
or when u are working inside a room put the hose outside thru the window and
switch the machine on.
When the gauges are in vacuum stop now.
Flash the system with nitrogen; it’s safe to start brazing now.
U can start repair the leak or replace the compressor.
Remove the line tap valve and put a new process line and a schrader valve on.
Vacuum as usual “till 500 microns” when charging use a scale because the
accuracy must be 1 or 2g. (look on the identification plate how much gram is
needed)
Remember it must be liquid charged.
R600a fridge is normally running in vacuum and high side around 500 to 700
Kpa.
Note: do not remove gauges when the fridge is running because it will suck in air
since its running in vacuum.
Double pinch the process line, then u can remove the gauges.
Cut off the schrader valve and close the process line by means of brazing it
close.
R600a is replacing R134a for domestic and R290 is replacing R22 and R404 for
commercial.
10. Definition of “retrofitting”
• retrofit - provide with parts, devices,
refrigerants or equipment not available or
in use at the time of the original
manufacture;
• "The old fridges / motor vehicles (R12) is
all been retrofitted with new refrigerants
and compressors”
12. Some qualifications and desirable
characteristics of a good refrigerant are:
• The boiling point or temperature, at which the refrigerant vaporizes,
must be low enough to provide the required cooling effect. Actually, the
boiling point of any refrigerant in a cooling unit is varied by the operating
pressure and can thus be raised or lowered as needed.
• Leaks should be easy to detect and locate. Do not have a chemical smell
at all times.
• It should be easy to lubricate parts moving in its presence. The
refrigerant should not react chemically with the lubricants and other
substances found in the refrigerator.
• It should not have an intoxication effect. It does not represent a risk for
the safety of the user (i.e; maintenance personal) or the public. A good
refrigerant has the right combination of safety and functionality. If there is
toxicity identified, the substance is a Class B refrigerant. Class 1
refrigerants are completely nonflammable, Class 2 types are moderately
flammable and Class 3 substances are highly flammable.
• It should comply with environmental aspects. (ozone friendly)
13. WINDOW AND SPLIT TYPE AIR-CONDITIONING
COMPRESSOR REPLACEMENT
• Disconnect electrical connections
• Recover refrigerant
• Disconnect suction and discharge
pipes
• Remove & replace compressors
• Flush your system
• Weld suction and discharge pipes
back
• Pressure test system
• Leak test system
• Evacuate system
• Reconnect electrical connections
• Charge system with refrigerant
• Check operation of system
