AHU Control Solution

Total Control System for Air Handling Units

Total Control System for Air Handling Units

Petra AHU control is a complete solution for the control of air handling units. It comprises the latest technologies in communication and design and replaces traditional hardwired solutions.

All system configuration and plant applications is performed via a user-friendly Web interface, which makes installation and commissioning a piece of cake.

The total integration of control and power electronics is unsurpassed in the industry and as your partner control and we know our responsibilities.

Your system must work – period!

Based on years of experience with HVAC products, Petra hereby presents a state-of-the-art system, focusing on maximum comfort and minimum energy consumption.

  • Full range of system components: from master controller and frequency converter to temperature and pressure sensors
    Specifically tailored for the users with Hand Terminal and web interface, ensuring maximum comfort and minimum energy consumption
  • Versatile solution with various operating modes
  • Alarm feature as standard
  • Software upgrade via SD memory card
  • Quick installation due to simple bus cable design Reliable

Total system for HVAC

The system includes all components required for controlling fans, electric and heating coils, cooling systems, drives for rotary heat exchangers and actuators in modern air handling units.

The system components communicate via state-of-the-art bus technology while external communication is handled via standard bus systems required by the market.

The master contains a high-performance processor unit and all interfaces into and out of the system.

Web programming

Through the built-in Web server, the system is configured via a standard IE browser on a PC.

Via a multi-level user interface, the administrator can set up various levels for different groups.

All the AHU operation is performed via the unique “Push & Turn” dial on hand terminal.

Cost-effective cabling

All peripheral units are connected to the master via a Modbus cable. This enables the system to be wired in a simple manner while retaining full control of all sub-units. This unique solution makes the system very cost-effective in installation, verification and commissioning.

The AHU can be factory assembled, including all internal installation and wiring, and can be easily unplugged and separated for transport before being reconnected on site.


Master controller can be connected to a variety of systems: Modbus RTU, Modbus TCP/IP, internal Web server, BACNET and LON.

Factory-mounted controls increase reliability

When AHU controls are installed at the jobsite, costs can go up and reliability can go down. To eliminate these problems, Solution AHUs can be equipped with Petra controls which are engineered, installed, and tested in the factory.

Factory-installation improves quality, saves time

While a Solution AHU is being manufactured, Petra Controls technicians can easily access all its segments. So, there are no accessibility problems to cramp the quality of the controls installation, which can occur on the jobsite. Also, all sensing probes have been pre-engineered to determine their best mounting location, ensuring accurate and reliable readings.

Factory-testing ensures accurate operation

Factory-mounted controls undergo a detailed testing process at the factory. The testing ensures that all wiring is installed correctly, and that all control panels and end devices work appropriately before the AHU is shipped. It also means that Solution AHUs can be up-and-running faster when they arrive on-site.

Factory-engineering speeds field connections

Solution AHUs are factory- engineered to simplify field connection of the controls. For example, coil valves are shipped uninstalled, but modbus connection between devices make quick-connects. In some instances, the AHU is too large to ship in one piece, and must be split. To ensure fast and easy jobsite assembly of the Petra controls, quick-connects (modbus-connection) come standard on all shipping splits.

Powerful ARM9 processor

Master controller communicates via RS485 Modbus and is based on the powerful ARM9 processor, which sets completely new standards for data processing and means that Master is future proof to an extent that has not previously been seen in the market. The operating system is based on Linux.

System Components Master

The master controller handles all processing and communication into and out of the system. It contains various interfaces for peripheral units, allowing sensors, pumps and valves to be connected to the master.

Hand terminal

The hand terminal, with its unique “Push & Turn” dial and graphical back-lit LCD, gives service technicians full control and surveillance of system operations.

Motor controls

EC controller and frequency converters control fan speed and are designed for mounting within the AHU or direct on motors. They are maintenance free and extremely rugged, providing years of dependable operation.


Fan IOs boards measure air flow and perform filter surveillance. The Fan IO can also control various sensors, alarm systems and actuators for heating and cooling systems or dampers.

Power controls

System power controls regulate electric heater capacity via 0-10 volt

Controller for rotary heat exchanger

The RHX controller and associated step motor regulate the rotary heat exchanger and are fully integrated via Modbus.

I/O extension

By connecting an extension module to the master via Modbus, subsidiary functions can be added to the AHU.

Lon module

The LON Gateway enables the system to communicate with other LON based systems, e.g. a BMS system.


Extensive range of PT-1000 temperature sensors is suitable for the system.

On site

Once installed, technicians perform final on-site checks and tests as well as setting energy optimization and other user- specific parameters.

Daily operation:

Facility managers operate the system via the Web interface or hand terminal. The user friendly design provides 100% control, ensuring maximum comfort with minimum energy consumption.

Temperature control modes:

  • Constant supply air temp.
  • Constant exhaust air temp.
  • Constant room temp.
  • Constant supply/exhaust differential temp.
  • Outdoor compensation
  • Summer/winter compensation
  • Recirculation heating minimum night temperature
  • Summer night cooling
  • Automatic summer/winter compensation
  • Forced cooling
  • Modulated recirculation

Fan control modes:

  • Constant flow
  • Constant pressure
  • Supply air pressure w. slave
  • Exhaust air pressure w. slave
  • Constant CO2
  • Low speed / high speed (recirculation)
  • Constant operation
  • Automatic operation


  • Fire in air handling unit
  • Fire in duct
  • Fire alarm
  • Functional testing of fire dampers
  • Electric heating
  • Hydronic heating
  • Counter flow heat exchanger
  • Cross-flow heat exchanger
  • Rotary heat exchanger
  • Economizer (free cooling)
  • Humidity control
  • Hydronic heat exchanger
  • Water-based cooling
  • Filter surveillance
  • Actuator control of dampers
  • Error log
  • Alarm handling
  • Combi battery, heating and cooling in one element
  • Control for external heat pumps
  • Automatic daylight saving
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