EN/07.2013/58/49
4.4.3. HGB (Hot Gas Bypass) control
The parameters involved are:
• S19 LIMIT SUPPLY TEMPERATURE IN FREECOOLING MODE: pre-set = 15 °C
• M44 BAND FOR LIMIT SUPPLY TEMPERATURE: pre-set = 5 °C
• M45 MINIMUM FREECOOLING DAMPER OPENING: pre-set = 0 %
• I67 SELECT RELAY HGB: pre-set = No connected
The HGB control is enabled only if the supply temperature probe is present.
If the HGB control is enabled and there are the conditions to enable the traditional freecooling, the freecooling damper
status is determined by the minimum value between the value calculated by standard freecooling control and that
calculated as described below:
– IF (TM < S19), DAMPER STATUS = M45
– IF (TM > (S19 + M44)), DAMPER STATUS = 100 %
– IF ((TM > S19) AND (TM < (S19 + M44)), DAMPER STATUS = MAX (M45, (100 / M44) * (TM - S19))
The HGB control can be associated to a relay by parameter I67.
If the machine is ON, the relay associated to the HGB control switches on if the supply temperature is lower than S19
and it switches off if the supply temperature is greater than S19 + M44.
If the machine is OFF, the relay associated to the HGB control is always off.
4.5. Emergency ventilation management
When there is a serious alarm, the emergency ventilation starts:
– Compressor is switched off
– Dirty filter alarm disabled
– Temperature management by freecooling damper and evaporator fan
4.6. Manual control
This part of the program allows to control manually the devices of the unit, excluding the automatic control but keeping
interlock with protections, to guarantee safety and integrity of all components.
The setting masks are under password.
It’s possible to get a manual control even if the unit is OFF.
To carry out the manual control you have to enter into “Manual control” menu from “System maintenance” menu, how it’s
described in par. 3.4.2.
In the following figure is shown the sub menu existing.
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