How to read the ventilation unit's technical data sheet?
The ventilation system’s technical data sheet is an accompanying document stating all relevant technical specifications describing the efficiency of the ventilation system. The technical data sheet also serves as the basis for application for Eco Fund’s subsidies, for the calculation of thermal savings, as well as for mutual comparison of systems’ efficiency. The sheet consists of 23 different criteria that can be used to compare different ventilation systems, while two criteria remain to stand out for their significance.
A regenerative heat recovery system is installed in unidirectional ventilation units – the energy of the outlet air is stored in the ceramic plate of the unidirectional ventilation system, helping inlet air acquire the desired properties (i.e. characteristics of indoor air). Bidirectional systems operate on the principle of recuperation – in this case the outlet air continuously transfers its properties to the inlet air within the heat exchanger, without interruptions or storing of energy in the plates.
Manufacturers of ventilation units often claim that their unit can achieve up to a 95% heat recovery rate. This is mostly true, but they often fail to mention at what air flow rate. The heat recovery rate is always higher at lower air flow rates. In this case the air travels slower and has more time to emit its properties to the inlet air. For example, the unit can operate in the 20-80m³/h air flow rate range. If the technical data sheet states that the measurements were carried out at a reference air flow rate of 30m³/h, and it achieved, e.g. a 78% heat recovery rate, the heat recovery rate at the maximum air flow (e.g. 80m³/h) will be significantly lower.
Na tej točki bomo nemalokrat slišali, da naprava redkokdaj deluje pri maksimalnem pretoku zraka, kar načeloma drži. A tudi takrat, ko naprava deluje pri nekem optimalnem, povprečnem pretoku 40m3/h bo rekuperacija zopet občutno nižja od 78%.