Home / modicon-m171-m172-plc-for-hvac-and-pumping-applications / Page 2-9

Modicon M171 M172 Plc For Hvac And Pumping Applications - Page 2-9 Solutions overview

2 1 3 4 5 6 7 8 9 10


Plant mode control


This Application Function Block (AFB) determines the operating mode for an Air Handling Unit. Besides monitoring the status of alarms, the AFB also monitors room and outdoor air temperatures to reduce cooling energy needs and improve comfort levels.


Monitored operation


The Air Handling Unit is set to a secure operation mode on detection of a fire alarm, fan alarm, or freeze state alarm


The night cycle function monitors room temperatures to help protect the building against condensation or other damage due to extreme indoor temperature conditions (too hot or too cold). Energy optimization


The night purge function purges and pre-cools the building during unoccupied periods to reduce cooling energy needs (free cooling).


The night cycle mode maintains a lower room temperature during heating periods and a higher room temperature during cooling periods to reduce the cooling or heating energy needs.

Operating principle

At start-up, the AFB checks the status of the alarms and the various operating modes, then automatically starts or stops the Air Handling Units.


This AFB can be used with all types of Air Handling Units. Typical applications


Air Handling Units


Solutions overview

Application solutions for HVAC

Related functions: Plant mode control

Previous Page
Next Page