Air handling unit controlling: recording statuses and performance per air handling unit preparation stage

What is the energy contribution of heat recovery in actual operation?

How does it behave at partial load, how at certain outside air conditions?

Is it likely that cooling and heating or heat recovery work against each other in some phases?

What proportion of power is supplied by the HRU, and what by the heater?


In existing HVAC systems, but also in systems currently undergoing IBN, Luftmeister measurement solutions reveal the control and ventilation reality. In each examined operating mode it becomes visible how the Mollier diagram (hx-diagram) is actually traversed. In this way, it is usually also possible to see which optimization possibilities exist.


About the method:

By measuring the central air mass flow as well as the enthalpy values before and after each treatment stage, the air energy meter allows all relevant information to be made available throughout. At the same time, it shows the thermal performance (and the total energy contributions over time).


The Technical City Hall in Freiburg is currently one of the most modern administrative buildings in Germany. In addition to its attractive architecture, it impresses with its high aspiration to become a "plus energy building", i.e. to supply more energy on balance than it receives during a year.

In order to guarantee maximum energy efficiency for the top-class air conditioning technology as well, the operator, Fraunhofer ISE, relies on Luftmeister technology. Specifically, enthalpy sensors were placed upstream and downstream of each relevant air treatment stage in the largest air conditioning center, and mass flow measurements of the air energy meter were placed in the supply air and exhaust air. Up to five enthalpy sensors can be connected to each air energy meter, so that four energy contributions can be determined (between them). On the basis of these useful energy values and numerous instantaneous values (flow rate, temperature, humidity, static pressure, etc.) also supplied by the air energy meter, the operator is able to optimize the climate control system in terms of energy.