6 - Microprocessor controls

The machine is available in four different operating con￿ 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 microproces￿ 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 adjust￿ 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 com￿ pressor, and minimum times, in order to guarantee the proper operation and to extend its life as much as pos￿ sible.

The activation of the Freecooling mode occurs as a func￿ 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 open￿ ing is varied in order to maintain the inside temperature equal to setpoint and as a function of the intake air tem￿ perature, which cannot be lower than a preset safety value.

Fig. a Compressor, heater and damper opening opera￿ tion

P Band

Freecooling mode

Heating

Set

Cooling

￿C

P Band

Compressor cooling mode

Heating Set Cooling ￿C

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 Freecool￿

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 deactivated 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:

￿compressor low pressure

￿compressor high pressure (reset on the pressure switch)

￿sensor fault

￿memory fault

￿fan fault (with optional sensors)

2)General warning - signalling of various failure conditions, among which:

￿high temperature

￿low temperature

￿heater thermostat (reset on the thermostat)

Notes:

￿ both the alarm and the warning must be reset manu￿ ally on the Microface.

￿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 Freecool￿ ing mode in the proper conditions.

￿The warning doesn't cause the unit to stop.

￿When the heater safety thermostat intervenes, the reset will be carried out on the thermostat (15) acces￿ sibble by removing the internal fan side panel.

6.1.3 - Optional alarm card

Besides the components described for the standard con￿ figuration, on the alarm card - which can be supplied as optional - there are relay contacts to obtain the follow￿ 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 Micro￿ face manual enclosed.

English

page 6

272014 - 04.02.2000