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English
Liebert HPM --- A/W/F/D/H
7.4 -- Checking the refrigeration piping pres-
sure drops
Liebert HPM is equipped with connections to check the refri-
geration piping pressure drops:
room unit → condenser → room unit
To carry out this operation it is necessary to use 2 calibrated
manometers and connect them as follows:
M1, connected to the compressor delivery valve;
M2, connected to theSchrader valve (2) of Fig. h.
When the compressor is ruuning, check M1 and M2.
N.B.: Repeat this test , inverting the manometers : tocalcula-
te the correct Δp consider the average value of the two
readings.
Refrigeration pipeline Pressure drops (Δp bar), at 45_C:
S At the same geodetic level: Δp ( b a r ) = M 1 --- M 2
S When condenser is above the room unit:
Δp (bar) = M1---M2+geodetic difference (m x 1,1:10,2)
S When condenser is below the room unit:
Δp (bar) = M1---M2 ---geodetic difference (m x 1,1:10,2)
Fig. h --- Refrigerant line components
7
6
5
4
3
2
1
connection
on the Liquid
Receiver
to the
evaporator
1 Liquid receiver valve
2 Filter dryer inlet Schrader valve
3 Filter dryer
4 Sight glass
5 Solenoid valve
6 Thermostatic expansion valve
7 Evaporator inlet Schrader valve
8 --- Operation
Unitoperation iscompletely automatic.The below sequence
explainshowtheunitoperates:
S The air, sucked in by the fan(s), enters the unit.
S The air is immediately filtered.
S The TEMPERATURE sensor or HUMITEMP (temperature
+ rel. humidity) sensor (check type installed), verifies the
state of the inlet air, and relays this information to the control
system.
S Filtered new air is injected into the air stream via the
Fresh Air Intake (optional).
S The treated air passes through the fans, which operate
continuously, and is then dispersed out of the unit.
S Under unit only: the air passe s from the underfloor void
into the room via air distribution outlets.
For ”UNDER” units installed on raised floor: switch
off the machine before removal of the floor panels
within a distance of 850 mm from the machine, to
avoid risks of contact with rotating devices (fans)
moving and with hot heating elements. (see Fig. i).
S The control system compares the relayed information to
the set point and proportional band values programmed
into its memory: it then commands the air conditioner to
treat the air as follows (see also Control manual):
S
COOLING
Direct expansion mode (DX)
The compressor is started and the cold refrigerant flows
through the evaporator, thus cooling the air passing over
it. For compressor operation see Control manual.
S
HEATING
Thiscan takeoneof threeforms:
--- electrical heating (optional): the heating elements
heat the air passing over them. There are 3 heating
steps.
--- hot water heating (optional):ifhotwaterisavailable,
this flows through the hot water coil, thus heating the
air passing over it. The hot water flow is contr olled by
a n o n --- o f f ( 3 --- w a y ) v a l v e .
--- hot gas reheat (optional used during dehumidifica-
tion): the hot refrigerant which exits the compressor
flows through the hot gas coil, thus heating the air
passing over it.
S DEHUMIDIFICATION --- optional
DX mode
One of the compres sors starts and either the air flow or
the evaporator surface is reduced (depending on the
model), thereby causing dehumidification (refer also to
Control manual).
In freecooling mode: see Control manual.
N.B.: If, during dehumidification, the ambient temperat-
ure drops below a specified level, dehumidification will
be stopped if necessary (see LOW LIMIT intervention in
Control manual).
S HUMIDIFICATION --- optional
The humidifier creates steam, which is distributed into
the air stream via the steam distribution pipe (see also
Enclosure A).
N.B.: Manual control can beperformed usingthe controlsys-
tem (see Control manual).
Fig. i --- Floor panels removal on a safety way
850 mm
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