Abstract: A heating and ventilation unit has a ceramic heat wheel rotatable within a housing between first and second plenums through which fresh and stale air, respectively, are forced to pass in a hot air ventilation system. The heat wheel is made of cordierite material such as is used in catalytic conversion systems for automobiles. It is formed with non-communicating and axially-extending parallel pores having a pore density of 62 pores per sq. cm. As it rotates the heat wheel transfers to the fresh air both the heat generated by a gas burner in the second plenum, and also low grate heat contained in the stale air. The burner is housed within a combustion housing by means of which the combustion gases are confined to a generally D-shaped area of the heat wheel.

Abstract: A gas fired boiler for a domestic hot water and/or central heating system has a burner (25) (FIG. 1), a static heat exchanger (22) through which water is circulated, and a rotary heat exchanger (12) of which the body is a disc of ceramic material such as is currently used for catalytic conversion in automobile exhaust systems. The rotary heat exchanger recovers heat from the gases passing from the static heat exchanger (22) to the outlet flue 4, and uses this recovered heat for heating the fresh air entering through the air intake (3). A conduit (90) having a controllable valve (91) enables heated fresh air to be supplied for space heating purposes if required, while improving the thermal efficiency of the boiler by promoting condensation of water vapor from the combustion gases as they pass through the rotary heat exchanger.