Operating Logics; Cooling Only Unit; Unit With Electrical Heating; Unit With Freecooling - Emerson Liebert HIROSS TD 06 Service Manual

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 ven-
tilate, activating the Freecooling as soon as the relevant condi-
tions are reached, automatically optimized in the event of mains
failure.
Important! For proper operation, the unit must be always fed
by 48VDC.
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 230/1/50
arranged by the user (UPS/generator), ensuring the operation
as in the 48 VDC version.
CAUTION: For safety reasons disconnect the QF1 and QF2 (if
present) switch when you want to stop the unit.

6 --- Operating logics

The units, in the different versions, are featured by the automatic
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
P
Band
Se
t

6.2 --- Unit with electrical heating

6.2.1 -- Control logic
For the heating and cooling version the control algorithm is
based on a one ---step adjustment for the compressor --- electric
heating and mechanical cooling. The control manages all its de-
lays in the activation of the compressor, as previously de-
scribed, so as to guarantee its correct operation and to make it
run times as long as possible.
6.2.2 -- Dead band
In this version the parameter "Dead band", in the "optional de-
vices" menu of the Microface microprocessor control is very im-
portant, and enables to transfer the heating semi ---band insert-
ing 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 tempera-
tures (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.
Cooling only
unit
Cooling
°C
Fig. b) Unit operation
1
/
2
Heating
Dead Band
1
/ Band
2
Heating

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---integral type for the cooling in the
Freecooling mode, with setting of the set point and proportional
band (P) (Fig. c).
The control manages all time 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. The activation of the Free-
cooling mode occurs as a function of the difference (that can be
set) between the inside temperature and the outside tempera-
ture. This means that if the difference between the two tempera-
tures increases beyond a certain value, the unit automatically
passes to the Freecooling function: the compressor is de ---acti-
vated and the analog output controls the 3---point servomotor of
the damper.
The damper opening is determined as a function of the differ-
ence between the outside and inside temperatures and as a
function of the intake air temperature, which cannot be lower
than a preset safety value. If the inside temperature exceeds the
proportional band by more than 20% for over 10 minutes, the
unit shifts to the compressor ---aided cooling and the Freecoo-
ling mode remains de ---activated for
If the inside temperature exceeds the proportional band by
more than 50% for over 2 minutes, the Freecooling mode is de ---
activated for 1 hour, and the unit shifts to cooling by means of
the refrigerating compressor.
Fig. c) Compressor, heater and damper opening opera-
tion
P Band
Heating
P Band
Heating
6.3.2 -- DX + FC (upon request, only)
In order to optimize the power absorption of the unit equipped
with freecooling, using the possible favourable outside condi-
tions, an application is available upon request, simultaneously
activating the mechanical cooling and the freecooling; all this is
automatically managed by the Microface microprocessor con-
trol according to a specific algorithm.
pag. 3
with electrical
P Band
Cooling and
1
Band / Band heating unit
2
Set point
Cooling
Cooling and
1
/ Band
heating unit
2
with Dead band
Set point Cooling
1
/ hour.
2
Freecooling
mode
Set Cooling
_C
Compressor
cooling mode
Set Cooling
_C
heating
°C
°C
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