27
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
12 - MAINTENANCE
Any technician attending the machine for any purpose must be
fully qualified to work on refrigerant and electrical circuits.
All refrigerant charging, removal and draining operations
must be carried out by a qualified technician and with the
correct material for the unit. Any inappropriate handling can
lead to uncontrolled fluid or pressure leaks.
WARNING: Before doing any work on the machine ensure
that the power is switched off. If a refrigerant circuit is opened,
it must be evacuated, recharged and tested for leaks. Before
any operation on a refrigerant circuit, it is necessary to
remove the complete refrigerant charge from the unit with a
refrigerant charge recovery group.
12.1 - General maintenance of the refrigerant circuit
•
Keep the unit itself and the space around it clean and free
of obstructions. Remove all rubbish such as packing
materials, as soon as the installation is completed.
•
Regularly clean the exposed pipework to remove all dust
and dirt. This makes detection of water leaks easier, and
they can be repaired before more serious faults develop.
•
Confirm that all screwed and bolted connections and
joints are secure. Secure connections prevent leaks and
vibration from developing.
•
Check that all insulation joints are securely closed and
that all insulation is firmly in place. Check all heat
exchangers and all pipework.
12.2 - Refrigerant charge
12.2.1 - Verification of the charge
CAUTION: The 30RA units are supplied with a precise
R407C refrigerant charge (see Physical Data table).
To verify the correct system charge prodeed as follows:
Ensure that no bubbles appear in the sight-glass, when operat-
ing the unit at full load for a while, at a saturated condensing
temperature of between 55 and 57°C. If necessary cover a sec-
tion of the coil surface to obtain this condensing temperature.
Under these conditions the apparent subcooling which is equal
to the saturated condensing temperature (1 - on the saturated
dew point curve) minus the liquid refrigerant temperature (3)
ahead of the expansion device must be between 12 and 14°C.
This corresponds to an actual subcooling temperature of
between 5 and 7 K at the condenser outlet, depending on the
unit type. Actual subcooling is equal the saturated liquid
temperature (2 - on the saturated bubble point curve) minus the
liquid refrigerant temperature (3) ahead of the expansion
device. Use the pressure tap supplied on the liquid piping to
charge refrigerant and to find out the pressure of the liquid
refrigerant. If the subcooling value is not correct, i.e. lower
than the specified values, a leak detection test must be carried
out on the unit, as it no longer contains its original charge.
Pressure
Enthalpy
In order to measure the liquid refrigerant pressure and tempera-
ture ahead of the expansion device, an access port must be
opened on the expansion device which causes a slight air bypass
on the condenser. Wait until unit operation has stabilized before
carrying out pressure and temperature measurements.
WARNING: To ensure proper operation of 30RA units there
must be at least 12 K of subcooling as the liquid refrigerant
enters the expansion valve.
The 30RA units use refrigerant. For your information, we are
reproducing here some extracts from the official publication
dealing with the design, installation, operation and
maintenance of air conditioning and refrigeration systems
and the training of people involved in these activities, agreed
by the air conditioning and refrigeration industry.
Apparent and actual subcooling
3
4
5
1
6
2
L
L + V
V
Содержание 30RA040B
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