Maintenance / Spare Parts; Routine Maintenance; Extraordinary Maintenance; Refrigerant Charging - Liebert HPS Service Manual

7 --- Maintenance / Spare parts

For safety reasons, always isolate the unit using the mains switch OFF, before opening the panels.
If installed:
AS THE MICROPROCESSOR CONTROL FEATURES AUTO-
MATIC RESTART (AFTER A SUPPLY INTERRUPTION), IT IS
RECOMMENDED THAT THIS FUNCTION IS DISABLED AND
THE MAINS SWITCH IS OPENED WHEN PERFORMING
ANY MAINTENANCE.

7.1 --- Routine maintenance

Maintenance program --- Monthly check
FANS
AIR FILTERS
ELECTRICAL CIRCUIT
REFRIGERATION CIRCUIT

7.2 --- Extraordinary maintenance

CAUTION:
If you need to intervene immediately after the
unit stops, wait 5 minutes before accessing the
inner parts, as you could get burnt.
7.2.1 --- Check of the system vacuum and leaks
NOTE:
Before proceeding, recover all the refrigerant, according to
the local laws.
1) Switch the unit off (main switch on OFF).
2) Remove the panels necessary for inspecting the refriger-
ating circuit.
3) Connect a high efficiency vacuum pump to the needle
valves (Schräder) on the gas and liquid lines; also ar-
range a connection with a nitrogen bottle.
4) Load the circuit with nitrogen (7 bar/700 kPa). Find poss-
ible leaks in the circuit by soapy water or other specific
product (foaming agents), and repair as necessary.
5) Drain the circuit by a vacuum of 0.3 mbar absolute.
6) After 3 hours check not to have exceeded 1.3 mbar abso-
lute; this condition ensures a humidity lower than 50 ppm
inside the system. If the vacuum is not kept there are still
leaks; repeat the operations from point 4.

7.2.2 --- Refrigerant charging

After having eliminated the humidity from the refrigerating cir-
cuit (see 7.2.1), proceed as follows:
1) Make sure all the unit components are in operating order.
Check that the fan motor rotates freely without any abnormal noise, and ensure that the
bearings are not running hot.
Also check the current absorption.
Check the conditions of the filters (3 for the recirculation air and 1 for the freecooling
air, if this option is included), if necessary, clean or replace them.
To replace the filters for the recirculation air:
Rotate the two filter---locking fasteners securing each filter.
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Remove the filters.
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Fit the spare parts.
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Lock the filters by rotating the two fasteners in the opposite direction to secure each
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filter.
To replace the filter for the freecooling air (if this option is included):
Remove the unit lower panel.
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Remove the fastening bracket and pull the filter vertically downwards.
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Fit the spare part.
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Reposition the bracket and close the panel.
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Check the power supply on all phases.
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Ensure that all electrical connections are tight.
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Check the evaporating pressures (to be performed by a refrigeration technician).
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Check the compressor current absorption, the head pressure and the presence of
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any unusual noise.
Ensure that there is no ice formation on the evaporator.
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pag. 6
On a daily basis, check the control readings for tempera-
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ture and, if shown, relative humidity.
The Maintenance Programme described below should
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be carried out by a skilled technician, preferably working
under a maintenance contract.
2) Using a charging hose, connect the cylinder to the liquid
line of the circuit. Drain the substances that cannot be
condensed from the hose.
Charge the circuit exclusively with the
refrigerant indicated on the identification
label.
Charge the quantity of refrigerant indicated in Tab. e.
3) Set the main switch on ON.
4) Start the compressor.
5) The charge operation can be considered finished when,
keeping the condensation temperature at a steady level
(~ 50_C, if necessary partially clog the condensing coil),
no more bubbles appear for at least ten minutes. Check
if the superheat in these conditions is 7---8 degrees.
Superheat calculation
a) With the unit operating in standard conditions,
measure the temperature of the suction line in the
point where the bulb of the thermal expansion valve
is fastened, in case of "HPSCxxA/L " version unit, in the
compressor inlet, in case of other versions.
b) Detect the evaporation pressure gauge temperature
from a pressure gauge placed on the compressor
suction.
c) Subtract the obtained temperature value from the
one measured in point a).
The difference is the superheat value.