Use of tracer gas to determine leakage in domestic heat recovery units (HRV).

Tracergases provide a way to determine airflows in different situations. In some cases it is the only way to get quantitative information. This paper presents two cases in which tracergases are used for measuring the internal leakage in heat recovery units. Internal leakage in heat recovery ventilators (HRV's) for domestic use may cause some problems: - the real quantity of fresh air entering the building is unknown - electrical power for the fans is used inefficiently - smelling air a.g. from the kitchen may re-enter the building due to cross leakage from exhaust air tot supply air - the efficiency of the HRV seems apparently better. Most commonly used in domestic buildings in The Netherlands is a cross-stream HRV. The internal leakage in three types of HRV's is measured using N,O as a tracergas. It is shown that major leakage occurs alongside the heat exchanger blok. Internal leakage in the heat exchanger itself however can not be neglected. The measurements show that an air leakage rate of less than 3 % of the total airflow can be obtained by careful design. Secondly is shown how internal air leakage in a (rotating valve) back flow heat recovery ventilator is measured. This type of heat recovery ventilator uses an accumulating mass to recover heat. Due to this principle a certain amount of leakage from exhaust air to supply air is unavoidable. The exact amount of air leakage can be measured using a continually sampling infra-red absorption analyser. With the results it was proved that the efficiency of the heat recovery was only minimal influenced by the leakage.