Extraordinary Maintenance - Hitecsa EWNLM 115 Manuel D'utilisation

II.9.1.4 Inspecting the hydraulic circuit
Check the water differential pressure switch: with unit running,
slowly close the interception valve positioned by the user on the water
inlet to the unit. If, during a test phase, the point is reached where the
isolating valve is completely closed without the differential pressure
valve cutting in, stop the unit immediately by pressing ON/OFF on the
control panel and replace the component.
Bleeding air from the chilled water system: by acting on the
relevant bleed valves positioned inside and outside the unit, it is
possible to evacuate the air trapped inside the hydraulic circuit. Always
check the pressure of the hydraulic plant and, if necessary, pressurise
with top-up water.
Circulator pump release (only 115-122 P1)
With the unit off, remove the right side panel and remove the screw that
holds the circulation pump. Turn the release screw located in the inside,
then put the screw that holds the circulation pump back in place.
Draining the hydraulic system: with unit off, if the unit must be
emptied, use the interception valves on the water inlet and outlet pipes.
Also use the drain present near to the water connections. In the models
equipped with pump, also use the drain present on the pump/circulation
pumps.
Inspection of the pump/circulation pump (where present): every
5000 functioning hours of the pump, the circuit board shows an alarm
without interruption of unit functioning. This is a warning that the pump
must be inspected. The inspection consists in the external cleanliness
and checking its general state.
Washing the water heat exchangers: plate exchangers are not
subject to particular fouling in rated running conditions. The working
temperatures of the unit, the speed of the water in the pipes and the
suitable finish of the heat exchanging surface reduce fouling of the
exchangers to a minimum. Any deposits on the heat exchanger can be
detected by measuring he pressure drop between the inlet pipes and
the unit outlet using a differential manometer and comparing the values
with those given in the tables in the attachments. Any sludge that may
form in the water circuit or any silt that cannot be trapped by the filter,
as well as extremely hard water conditions or high concentrations of
any antifreeze solution used, may clog the exchangers and undermine
their heat exchanging efficiency. In this case, it is necessary to wash
the exchanger with suitable chemical detergents, setting-up the already
existing plant with adequate load and unload couplings or intervening
as in the figure. A tank must be used containing light acid, 5%
phosphoric acid or if the exchanger must be cleaned frequently, 5%
oxalic acid. The detergent liquid must be made to circulate inside the
exchanger at a flow rate of at least 1.5 times the nominal work value.
With a first circulation of the detergent, maximum cleaning is performed,
successively, with clean detergent, the definitive cleaning is carried out.
Before re-starting the system, it must be rinsed thoroughly to eliminate
all traces of the acid and the air in the system must be bled, eventually
be re-starting the user pump.
1. Unit;
2. Auxiliary valve;
3. Interception valve;
4. Washing pump:
5. Filter;
6. Acid tank.
SECTION II: INSTALLATION AND MAINTENANCE
II.9.2

EXTRAORDINARY MAINTENANCE

II.9.2.1 Instructions for repairs an replacement of
components
When a component of the refrigerant circuit or the unit must be
replaced, the indications given below must be considered:
Always refer to the wiring diagrams attached to the machine
whenever and electrically powered component must be replaced,
making sure that every wire that must be disconnected is identified in
order to prevent errors in a successive re-wiring phase.
When machine functioning is restored, it is always necessary to
repeat the operations in the start-up phase.
II.9.2.2 Instructions for emptying the refrigerant
circuit
To empty the entire refrigerant circuit using type-approved appliances,
recover the refrigerant fluid from the high and low pressure sides and
also from the liquid line. The load couplings are used, which are present
in every section of the refrigerant circuit All of the circuit lines must be
recovered because only in this way is it sure that all refrigerant fluid has
been completely removed. If you apply a brazing torch to one of the
low-pressure components of the system, the pressurised mixture of
refrigerant and oil could blow out of the circuit and ignite on contact with
the brazing torch. To prevent this risk, it is important to check the
effective unload of the pressure on all branches, before welding. All of
the refrigerant fluid unloaded cannot be disposed of in the environment
because it is a pollutant, but must be recovered using suitable
containers and taken to an authorised collection centre.
II.9.2.3 Elimination of humidity from the circuit
I humidity is present inside the machine during functioning, it must be
emptied completely from refrigerant fluid and the cause of the problem
must be eliminated. If the humidity is to be eliminated, the maintenance
technician must dry the system using a vacuum up to 70Pa,
successively the refrigerant fluid load can be restored, which is
indicated on the plate positioned on the unit.
II.9.2.4 Replacing the drier filter
To replace the dryer filter, carry out emptying and eliminate the humidity
from the refrigerant circuit of the unit, thus evacuating the refrigerant
dissolved in the oil.
Once the filter has been replaced, perform the vacuum on the circuit
again to eliminate any traces of uncondensed gas, which may have
entered during the replacement operation. Check that there are no gas
leaks before putting the unit back into normal working conditions.
II.9.2.5 Integration-top-up of the refrigerant load
The units are factory inspected with the load of gas necessary for their
correct functioning. The amount of gas contained inside the circuit is
indicated directly on the serial plate.
If the load of R410A must be reset, the emptying program must be
performed along with evacuation of the circuit, eliminating the traces of
uncondensed gases with any humidity. The gas load must be restored
following a maintenance intervention on the refrigerant circuit following
thorough washing of the same. Successively, restore the exact amount
of refrigerant and new oil, as stated on the serial plate. The refrigerant
must be drawn from the container in the liquid state in order to
guarantee the correct proportion of the mixture (R32/R125).
At the end of the loading operation it is necessary to repeat the unit
start-up procedure and monitor the unit work conditions for at least 24
h. If, for particular reasons, e.g. a refrigerant leak a simple top-up is
required, a slight decrease in unit performance must be considered. In
all cases, reintegration must be performed on the low pressure branch
of the machine, before the evaporator, using the pressure points
prepared for this purpose; attention must also be paid to introducing
refrigerant only in the liquid state.
39