The pressure switch is also referred to as a combustion air switch or draft proving switch. 1. 74. Switch closes when the combustion/booster motor runs creating a negative air pressure. Model # 632444 Features: Combustion air switch Draft proving switch Switch closes when the combustion/booster motor runs creating a negative air pressure Item Dimensions: 4. 09" L x 3. 78" W x 1. 65" H.
