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9 - MaINTENaNCE
During the unit operating life the service checks and tests
must be carried out in accordance with applicable national
regulations.
If there are no similar criteria in local regulations, the
information on checks during operation in annex C of
standard EN 378-2 can be used.
External visual checks: annex D of standard EN 378-2.
These controls must be carried out:
•
After an intervention that is likely to affect the resis-
tance or a change in use or change of high-pressure
refrigerant, or after a shut down of more than two years.
Components that do not comply, must be changed.
Test pressures above the respective component design
pressure must not be applied (annex B and D).
•
After repair or significant modifications or significant
system or component extension (annex B).
•
After re-installation at another site (annexes A, B and D).
•
After repair following a refrigerant leak (annex D).
The frequency of refrigerant leak detection can vary
from once per year for systems with less than 1% leak
rate per year to once a day for systems with a leak
rate of 35% per year or more. The frequency is in
proportion with the leak rate.
NOTE: high leak rates are not acceptable. The necessary
steps must be taken to eliminate any leak detected.
NOTE 2: fixed refrigerant detectors are not leak detectors,
as they cannot locate the leak.
9.1 - soldering and welding
Component, piping and connection soldering and welding
operations must be carried out using the correct procedures
and by qualified operators. Pressurised containers must not
be subjected to shocks, nor to large temperature variations
during maintenance and repair operations.
Any technician attending the machine for any purpose must
be fully qualified to work on refrigerant and electrical
circuits.
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.
All refrigerant 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.
If an oil draining or recovery operation becomes necessary,
the fluid transfer must be made using mobile containers.
9.2 - 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.
9.2.1 - Verification of the refrigerant charge
CAUTION: The 30hZ/hZV units are supplied with a
precise 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 ope-
rating the unit at full load for a while. Under these conditions
the apparent subcooling which is equal to the saturated con-
densing 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 corre-
sponds 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 refri-
gerant. 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.
WARNINg: To ensure proper operation of 30hZ/hZV
units there must be at least 12 K of subcooling as the
liquid refrigerant enters the expansion valve.
The 30hZ/hZV units use refrigerant. for your information,
we are reproducing here some extracts from the official
publication dealing with the design, installation, opera-
tion and maintenance of air conditioning and refrigeration
systems and the training of people involved in these acti-
vities, agreed by the air conditioning and refrigeration
industry.