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Introduction of Control System for Air Handling Units
As one of the top class manufacturers in air conditioning field, Carrier provides an integrative AHU
control system to meet with comfort demands of customers as well as to be optimized for different
application requirements.
1. General introduction
The integrative control solution with variable-frequency drive covers the common demands of AHU
control functions. The human-computer interface (HMI) with graphical display is inserted into control box
panel for easy operation. Factory-mounted integrated control components help to save installation time and
maintenance cost, as well as to ensure optimal operation of AHUs.
¾ The system has accurate control on fan speed, water valve opening and damper opening, by its
internal PID calculation on the change of setting temperature and indoor load.
¾ The system has control on timing on/off of AHUs by HMI, which is convenient for routine
maintenance.
¾ The system has flexible operating mode for customer choice, both remote and local mode
available for different application.
¾ The system has continuous monitoring on electric loop and equips with quick-checking function,
which is used to test the AHU input and output.
¾ Field controller controls on supply fan on/off and collect signs of on/off status, fault alarm and
operating mode etc.
¾ Field controller can automaticly turn on/turn off AHUs by working/holiday logic or accident logic.
¾ Field controllers record AHUs accumulated operating time and shows maintenance reminding
notes if the time gets to limitation.
¾ HMI shows fault alarming once there is fault for AHUs operation.
¾ Interlocking control on cold/hot water electric two-way valve, fresh air damper and supply fan,
which means the valve and damper will close automaticly once supply fan turns off.
¾ Optional CO2 detector helps to control the opening of fresh air damper by monitoring room CO2
concentration.
2. AHU operation mode
Three operating modes are available for AHU equipped with control system,
2.1 Remote Mode: The unit will be controlled by remote control contact (passive contact) when
setting remote button at Remote Mode.
2.2 Local Mode: The unit can run at either automatic mode or manual mode, which is controlled by
HMI.
1εAutomatic Mode : When setting remote button at automatic mode, the unit will be controlled
automatically by touch screem.
2εManual Mode: When setting remote button to Local Mode, customer can start the fan in case of
control system failure. In Manual Mode, customer can only adjust air volume but can’t have demand of
indoor temperature change.
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