Patent ID: 8459569

Claim:
A heating unit located within an interior space including a first set of rooms and a second set of rooms, the second set of rooms not having any rooms in common with the first set of rooms, comprising: a primary heater for generating primary combustion gases; a heat exchanger including: a fresh air input for receiving fresh air from outside the interior space; a return air input for receiving return air from the first set of rooms; a supply air output connected to the fresh air input and the return air input for supplying air to the first and second sets of rooms; a combustion gas input for receiving the primary combustion gases from the primary heater; an exhaust air input for receiving exhaust air from the second set of rooms; an exhaust air output connected to the combustion gas input and the exhaust air input; whereby heat is exchanged from the primary combustion gases to the return air or from the exhaust air to the fresh air; a first fan for drawing the primary combustion gases and the exhaust air through the heat exchanger, and for exhausting the primary combustion gases and the exhaust air outside the interior space; a second fan for drawing in the return air from the first set of rooms or fresh air from outside the living space, and for blowing out the supply air into the first and second rooms; and a controller for switching between a heating mode in which the primary combustion gases heat the return air, and a heat recovery mode in which the exhaust air heats fresh air.