Abstract: A control unit for make-up air and combustion air is disclosed for use with a furnace in an air circulating system for a building. A baffle having a combustion air inlet and a make-up air inlet is provided with a weather protective hood and adapted to be mounted on the outside wall of a building. The combustion air inlet is connected through a conduit to a location adjacent the floor of the building on which the furnace is mounted. The baffle includes a restrictor plate including a pair of openings aligned with the combustion air and make-up inlets, respectively, and including a screen extending across the openings. The baffle includes a damper in the make-up air inlet which opens in response to reduced pressure in the furnace return air duct so that the inside pressure tends to be equalized with the outside pressure.

Abstract: A control unit for make-up air and combustion air is disclosed for use with a furnace in an air circulating system for a building. A baffle having a combustion air inlet and a make-up air inlet is provided with a weather protective hood and adapted to be mounted on the outside wall of a building. The combustion air inlet is connected through a conduit to a location adjacent the floor of the building on which the furnace is mounted. The baffle includes a restrictor plate including a pair of openings aligned with the combustion air and make-up air inlets, respectively, and a screen extending across the openings. The baffle includes a damper in the make-up air inlet and a damper in the combustion air inlet. The dampers are mounted on a common shaft so that they move concurrently in response to a pressure differential between the inside and outside.