Passive mixing circuit
- Dennis De Beuckeleer
Operating principle
The passive mixing circuit controls the net thermal power passing through the circuit by mixing cold return water (coming from the end unit return pipes) with hot water from the primary production side. In full-load operation, the 2-way valve is completely opened whereas in partial load conditions the 2-way valve is positioned in the function of the process value (measured water temperature) and setpoint (heating curve).
Individual components and parameters
Secondary pump
2-way valve
Balance valve for pump
Balance valve for primary balancing
System check
As this mixing circuit is a so called 'passive' circuit, the circuit needs a primary pump to extract hot water from the primary side. If the software encounters a missing pump on the primary side of the passive mixing circuit, it will report this as a problem while running the system check.
Design flow and temperature regime propagation
By running the action "compute design flows" all the design flows are calculated based on the power and temperature regime of the end units. In case where there are multiple types of end units (radiators, floor heating, ...) the supply temperature in regime may differ. The bypass in the passive mixing circuit guarantees a maximum supply temperature (45°C) for the floor heating, because of the mixing point on the supply pipe. Note that the primary temperature difference from the floor heating is larger than that of the radiators, which will influence the design flow.