Vertiv Liebert HPW Series, Руководство пользователя

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pag. 3
Freecooling -- (Fig. 11 and Fig. 12)
When the outdoor temperature is lower than the indoor one,
the integrated modulating damper does open/close to cool the
room with external air: compressor is off. The exhaust warmer
air is automatically rejected outside through the unit, without
any additional louver (e.g. overpressure damper). The para-
meters can be adjusted. A dedicated temperature sensor is
present in the air delivery section to prevent the air from
enter-ing the room at too low temperatures (adjustable
parameter). The unit is further equipped with a washable
metal filter next to the outside air suction inlet. When the
expected conditions oc-cur, the servocontrol, managed by the
microprocessor control, opens the movable damper
separating the flows of the inside and outside air. In this way
the outside air, sucked by the fan, flows inside the room and
is discharged through the openings of the freecooling
compartment. The opening degree of the damper is
determined as a function of the set point value to be kept and
of the intake air temperature (see Chap. 6).
5.1 --- Adjustment of the condenser fan
speed
(optional)
A sensor is positioned so as to detect constantly the
condens-ing pressure of the refrigeration gas. On the basis
of this in-formation, an electronic device ( Variex ) modulates
the fan ro-tation speed in order to keep the condensing
pressure within the allowed values. In this way, besides
optimizing the com-pressor operation, you can have a
remarkable reduction of the sound pressure level (mainly
during the night), an easier start---up of the compressor at
low temperatures and some en-ergy saving.
For the calibration of the speed adjuster refer to chap. 7.
5.2 --- Emergency cooling (optional)
5.2.1 -- Emergency cooling 48VDC
The 48 VDC emergency cooling provides for the evaporating
fans, the freecooling damper and the control to be always sup-
plied at 48 VDC, while the compressor, the condensing fan
and the heaters are connected with the AC mains. If the AC
main supply fails, the conditioner does not stop but
continues to ventilate, activating the integrated Freecooling
as soon as the relevant conditions are reached,
automatically optimized in emergency.
Important!
For proper operation, the unit must be always
fed by 48VDC.
CAUTION:
For safety reasons disconnect the QF1 and
QF3 switches (only QF1 for units in “no emergency cooling
ver-sion”) when you want to stop the unit.
5.2.2 -- Emergency cooling 230VAC-- 50Hz
In case of AC mains failure, the treating fans, the control
and the damper servomotor are supplied by the second
line at 230V/1Ph/50Hz arranged by the user (UPS/generator),
ensur-ing the operation as in the 48 VDC version.
6 --- Operating logics
The units, in the different versions, are featured by the auto-
matic operating logics specified here below.
6.1 --- Cooling only unit
6.1.1 -- Control logic
The control algorithm is based on a one---step adjustment for
the mechanical cooling with compressor: the control manages
all the activation delays, so as to ensure the correct
operation and extend the operating life as much as possible.
Fig. a) Operation of the cooling only unit
Set Cooling
°
C
Cooling only unit
P Band
6.2 --- Unit with electrical heating
6.2.1 -- Control logic
For the hot and cold version the control algorithm is based on a
one---step adjustment for the compressor---aided electric
heating and mechanical cooling. The control manages all its
lags in the activation of the compressor, as previously de-
scribed, so as to guarantee its correct operation and to make it
function as long as possible.
6.2.2 -- Dead band
In this version the parameter “Dead band”, in the “optional
devices” menu of themicroprocessor control is very important,
and enables to transfer the heating semi---band inserting a
non---sensitive area (ventilation only) between the set point
temperature and the start of the heating semi---bands (see
Fig. b). In this way, without having to modify the proportional
band, the electric heating can be activated at lower temperat-
ures (according to the value set for the dead band) compared
to the standard setting, consequently reducing the power con-
sumption of the heaters and optimizing their operation accord-
ing to the site requirements.
Fig. b) Unit operation with electrical heating
Heating Cooling °C
P Band
Dead Band
Set point Cooling Heating
°
C
1
/
2
Band
1
/
2
Band
1
/
2
Band
1
/
2
Band
Set point
Cooling and
heating unit
Cooling and
heating unit
with Dead
band
6.3 --- Unit with freecooling
6.3.1 -- Control logic
The control algorithm is based on a single---stage adjustment
for the heating and cooling with the compressor and on an
ad-justment of the proportional---
integrative type for the cooling in the Freecooling mode, with
setting of the set point and propor-tional band (P) (Fig. c).
The control manages all activation delays of the compressor,
as we have seen in the 2 previous cases, in order to
guarantee the proper operation and to extend its life as much
as possible. The activation of the Freecooling mode occurs as
a function of the difference (that can be set) between
the inside temperature and the outside temperature.
This means that if the difference between the two temperatures
increases beyond a certain value, the unit automatically
passes to the Freecooling function: the compressor is de---
ac-tivated and the analog output controls the 3---point
servomotor of the damper. The damper opening is
determined as a functionof thedifferencebetween
theoutsideand insidetemperat-ures and as a function of the
intake air temperature, which can-not be lower than a preset
safety value. If the inside temperat-ure exceeds the
proportional band by more than 20% for over 10 minutes, the
unit shifts to the compressor---aided cooling and the
Freecooling mode remains de---activated for
1
/
2
hour. If the
inside temperature exceeds the proportional band by