User Manual

11
3.3.3 ERC strategy
Advantages:
– Optimal use of ERC
The position signals are converted into demand signals for the ERC strategy
(Figure 3-1) and weighted using specific costs for heating, cooling, humidification
and dehumidification. Weighting can be set for each plant to allow for cost-
optimized operation of the plant. The tx2-algorithm then calculates the positioning
signal for heat recovery from the weighted demand signals so that the mixed air or
air state after ERC continues to be conditioned by the follow-on air handling
aggregates at minimum energy expense and costs.
Energy recovery is controlled so that the sum of all weighted demand signals for
heating, cooling, humidification, and dehumidification is minimized. The ERC
strategy is based on the t,x diagram. Each process is assigned a vector at the t,x
level (Figure 3-5) and weighting (Section 3.3.6). The vectors reflect the theoretical
impact of each process. During operation, only two vectors can be active at any
given time in addition to the ERC vector.
The supply air setpoint is at the center of the diagram. In addition, the model shows
the actual values for room and outside air. The ERC vector results from this,
depending on the degree of recovery for temperature and humidity, based on the
actual value for outside air.
The aim is to identify the point on the ERC vector that minimizes the sum of the
theoretical impact of both active processes.
Example:
The outside air is cooler than the room air. ERC also should condition cooler air,
thereby increasing the amount of outside air, if cooling demand is high. This action
reduces the required cooling energy. If humidification is required at the same time,
an additional dimension is added (Section 3.3.5).
Figure 3-5: t,x diagram