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6.3.2 - Refrigerant guidelines
Refrigeration installations must be inspected and maintained
regularly and rigorously by specialists. Their activities must be
overseen and checked by properly trained people. To minimise
discharge to the atmosphere, refrigerants and lubricating oil
must be transferred using methods which reduce leaks and
losses to a minimum.
-
Leaks must be repaired immediately
-
A valve on the condenser liquid refrigerant outlet line
enables the refrigerant charge to be transferred to the
receiver provided specifically for this purpose (not
supplied).
-
If the residual pressure is too low to make the transfer
alone, a purpose-built refrigerant recovery unit must be
used.
-
Compressor lubricating oil contains refrigerant. Any oil
drained from a system during maintenance must therefore
be handled and stored accordingly.
-
Refrigerant under pressure must never be discharged to
the atmosphere.
6.3.3 - Recharging liquid refrigerant
CAUTION: 30SZ units are charged with liquid HFC-407C
refrigerant.
This zeotropic refrigerant consists of 23% R-32, 25% of R-125
and 52% R-134a, and is characterised by the fact that at the
time of the change in state the temperature of the liquid/vapour
mixture is not constant, as with azeotropic refrigerants. All
checks must be made, using the appropriate pressure/tempera-
ture diagram.
Leak detection is especially important for units charged with
refrigerant R-407C. A refrigerant leak in the liquid or vapour
phase will have an effect on the composition of the remaining
fluid.
NOTE: Regularly carry out leak checks and immediately
repair any leak found.
6.3.4 - Undercharge
If there is not enough refrigerant in the system, this is indicated
by gas bubbles in the moisture sight glass. There are two
possiblities:
•
Small undercharge (bubbles in the sight glass, no
significant change in suction pressure).
-
After detection and repair the unit can be recharged.
-
The replenishment of the charge must always be
done in the liquid phase at the liquid line. The
refrigerant cylinder must contain a minimum of 10%
of its initial charge.
•
Significant undercharge (large bubbles in the sight glass,
drop in suction pressure).
-
Small units (charge below 20 kg per circuit).
Completely drain the refrigerant charge, using a
refrigerant recovery unit, repair and then recharge
completely, following the precautions given above.
-
Large units (charge above 20 kg per circuit).
After detection and repair completely recharge the
unit as described above, operate it for a few minutes
and then let a specialist carry out a chromatographic
analysis to verify the composition of the blend (range:
R-32: 22-24%, R-125: 23-27%, R-134a: 50-54%).
WARNING: If brazing is necessary, it should be done in a
neutral atmosphere: nitrogen. Combustion of refrigerant
produces toxic phosgene gas.
VERY IMPORTANT:
-
Never use the compressor to pump down the system.
-
Never introduce liquid refrigerant into the suction line.
-
Do not overcharge the system with refrigerant.
