Having one fan switched off during the summer (non-heating) cannot generally be considered a thermal bypass facility. It is only accepted as a bypass facility if the air volume flow in bypass mode is supported by supply/exhaust grills (openings) in the façade. Additionally, the same information requirements for installation instructions of unidirectional ventilation systems must be followed as described in Annex IV.
For bi-directional RVUs with one fan switched off as a bypass facility, it is deemed necessary that:
- The CTRL factor for central demand control (for the calculation of SEC) can only be used if these openings are also regulated by the control system of the units. The performance of the main fan(s) and the opening(s) are to be controlled according to the central demands.
- The CTRL factor for local demand control (for the calculation of SEC) can only be used if these openings are also regulated by local demands by the control system of the unit. The performance of the main fan(s) and the openings are to be controlled according to local demands.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.