Standard Hydraulic Solutions

QM Holzheizwerke® recommends using standard hydraulic solutions whenever possible. If a standard hydraulic solution is chosen, the design and functional description of the system is particularly simple: Calculations are made in prepared tables and questions about the system concept can be answered by simply ticking a box. This enables efficient quality assurance and reduces planning errors to a minimum.

Documents and templates in English providing further information on standard hydraulic solutions according to the QM system are in progress and will be made available as soon as possible.


The selection and description of the standard hydraulic solutions follows eight previously established principles:

  1. One proven hydraulic scheme for each heat generation application.

  2. Heat generation can be extended hydraulically and in terms of control technology as required. An exception was only made for the monovalent wood heating system without storage tank, where a minimum solution is permitted in addition to the regular solution, but which cannot be extended.

  3. The leading boiler and the following boiler are not hydraulically defined. This means that only parallel circuits are used for heat generation (no series circuits).

  4. The control variable of the main controller is
    - the main flow temperature for systems without storage tank
    - the storage charging status for systems with storage tank.

  5. The control variable of the main controller is always the setpoint value of the firing rate of the internal wood boiler controller, e.g. in the sequence boiler 1 two-point - boiler 1 continuous - boiler 2 two-point - boiler 2 continuous.

  6. Strict coupling of hydraulic circuits with low pressure difference. This means that there is always a generously dimensioned bypass ("hydraulic separation") between two hydraulic circuits (each with its own pump).

  7. All heat consumer circuits for the lowest possible return temperature  
    - in the central unit with a low-pressure-differential connection
    - at the district heating pipelines with a pressure-differential connection.

  8. Compliance with minimum valve authorities:
    - 3-way valves greater than 0.5
    - Straight way valves greater than 0.3