Investigation of a domestic heating system with ventilation heat recovery : performance and integrity.

Domestic heating systems with a heat exchanger are generally assessed for efficiency by the ratio of primary energy input delivered energy output. In practice, performance depends on all the components in the heat delivery system and on their matching. In the air heating system addressed here, the components include: the gas burning air heater, supply ducts, return ducts, heat recovery system, controls, fans, filters and pumps. This paper describes experiments conducted on a test house in Bath during the years 1991 to 1993. The house has been retrofitted with an air heating system and a ventilation heat recovery unit which also recovers heat from flue gases. The aim of these experiments was to characterize the house and the retrofit system in terms of ventilation and energy performance. In particular. airflows through the heat exchanger the heat losses occurring in the ducts and the air leakage from the ducts to the crawl space were investigated . To match the real values most of the experiments were conducted with the settings of the house as used by the occupants. This included the thermostat, the position of the delivery grilles and the window openings. Tracer gases have been used extensively to measure air change rates and an original method to assess air leakage from ducts has been developed.