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page 6
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272014 - 04.02.2000
6 - Microprocessor controls
The machine is available in four different operating conĆ
figurations:
1) chill unit only;
2) chill and hot unit;
3) unit with freecooling, chill only;
4) unit with freecooling, chill and hot.
All versions are equipped with the new Microface
microprocessor control.
6.1 - Control logic
These units are managed by the Microface microprocesĆ
sor control and may be combined with the Hiromatic
control for the complete monitoring of all unit operation
parameters (see enclosed manual).
The control algorithm is based on a single-stage adjustĆ
ment for the heating and cooling with the compressor
and on an adjustment of the proportional-integrative
type for the cooling in the Freecooling mode, with setting
of the set point and proportional band (P) (Fig. d.)
The control manages all activation delays of the comĆ
pressor, and minimum times, in order to guarantee the
proper operation and to extend its life as much as posĆ
sible.
The activation of the Freecooling mode occurs as a funcĆ
tion of the difference (that can be set) between the inside
temperature and the outside temperature. This means
that if the difference between the 2 temperatures
increases beyond a certain value, the unit automatically
passes to the Freecooling function: the compressor is
de-activated and the analog output controls the
3-point servomotor of the damper. The damper openĆ
ing is varied in order to maintain the inside temperature
equal to setpoint and as a function of the intake air temĆ
perature, which cannot be lower than a preset safety
value.
Fig. a Compressor, heater and damper opening operaĆ
tion
Set CoolingHeating _C
Set CoolingHeating _C
Freecooling
mode
Compressor
cooling mode
P Band
P Band
If the inside temperature exceeds the proportional band
by more than 20% for longer than 10 minutes, the unit
passes to the cooling with compressor and the FreecoolĆ
ing mode remains de-activated for
1
/
2
hour. If the inside
temperature exceeds the proportional band by more
than 50%, the Freecooling mode is immediately de-
activated and remains in this condition for
1
/
2
hour and
the cooling by refrigerating compressor intervenes.
6.1.1 - Start-Stop
Altogether there are three ways for starting or stopping
the unit:
a) the isolator switch inside the electrical panel;
b) the digital input of the Microface card;
c) the ON-OFF push button on the Hiromatic interface
(optional).
Priority: a) b) c) must be considered as 3 series contacts;
only if all contacts are on, the unit can operate.
6.1.2 - Alarm control
The terminal board of the elertical panel is provided with
2 clean exchange contacts, on standard configuration,
used as follows:
1) General alarm:
S compressor low pressure
S compressor high pressure (reset on the pressure
switch)
S sensor fault
S memory fault
S fan fault (with optional sensors)
2) General warning - signalling of various failure
conditions, among which:
S high temperature
S low temperature
S heater thermostat (reset on the thermostat)
Notes:
S both the alarm and the warning must be reset manuĆ
ally on the Microface.
S An alarm causes the unit to stop and the unit in
stand-by (if available) to intervene. If the unit is in
stand-alone, the high and low pressure alarms don't
stop the machine to allow the operation in FreecoolĆ
ing mode in the proper conditions.
S The warning doesn't cause the unit to stop.
S When the heater safety thermostat intervenes, the
reset will be carried out on the thermostat (15) accesĆ
sibble by removing the internal fan side panel.
6.1.3 - Optional alarm card
Besides the components described for the standard conĆ
figuration, on the alarm card - which can be supplied as
optional - there are relay contacts to obtain the followĆ
ing alarms separated:
1) compressor high and low pressure
2) Clogged filter alarm
3) Fan fault
4) High temperature
5) Low temperature
These alarms cause the unit to stop in the same ways as
described in the previous paragraph.
For the detailed description of the alarms, see the MicroĆ
face manual enclosed.