26
Leak detection is especially important for units charged
with refrigerant R-407C. Depending on whether the leak
occurs in the liquid or in the vapour phase, the proportion
of the different components in the remaining liquid is not
the same.
NOTE: Regularly carry out leak checks and immediately
repair any leak found.
9.2.4 - Undercharge
If there is not enough refrigerant in the system, this is indi-
cated by gas bubbles in the moisture sight-glass.
If the undercharge is significant, large bubbles appear in the
moisture sight-glass, and the suction pressure drops. The
compressor suction superheat is also high. The machine
must be recharged after the leak has been repaired.
Find the leak and completely drain the system with a refri-
gerant recovery unit. Carry out the repair, leak test and
then recharge the system.
IMPORTANT: After the leak has been repaired, the circuit
must be tested, without exceeding the maximum low-side
operating pressure shown on the unit name plate.
The refrigerant must always be recharged in the liquid
phase into the liquid line.
The refrigerant cylinder must always contain at least 10%
of its initial charge.
For the refrigerant quantity per circuit, refer to the data on
the unit name plate.
9.2.5 - Characteristics of R-407C
See the table on the following page.
Saturated bubble point temperatures (bubble point curve).
Saturated dew point temperatures (dew point curve).
9.3 - Electrical maintenance
When working on the unit comply with all safety precau-
tions decribed in section 1.2.
•
It is strongly recommended to change the fuses in the
units every 15000 operating hours or every 3 years.
•
It is recommended to verify that all electrical connec-
tions are tight:
a. after the unit has been received at the moment of
installation and before the first start-up,
b. one month after the first start-up,when the elec-
trical components have reached their nominal
operating temperatures,
c. then regularly once a year.
apparent and actual subcooling
R-407C
Pressure
Enthalpy
legend
1
Saturated condensing temperature at the dew point
2
Saturated liquid temperature at the bubble point
3
Liquid refrigerant temperature
4
Saturation curve at the dew point
5
Saturation curbe at the bubble point
6
Isotherms
7
Apparent subcooling (1 - 3)
8
Real subcooling (2 - 3)
L
Liquid
L + V
vapour
V
Vapour
9.2.2 - 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.
•
All units are equipped with two special connections
on the suction and liquid line, which permit the con-
nection of quick-connect recovery valves without loss
of refrigerant.
•
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.
9.2.3 - Recharging liquid refrigerant
CAUTION: 30hZ units are charged with liquid hfC-
407C refrigerant.
This non-azeotropic refrigerant blend 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 tempe-
rature of the liquid/vapour mixture is not constant, as with
azeotropic refrigerants. All checks must be pressure tests,
and the appropriate pressure/temperature ratio table must
be used to determine the corresponding saturated tempe-
ratures (saturated bubble point curve or saturated dew
point curve).
3
4
5
1
6
2
L
L + V
V
