While the 3155 series typically requires a single gasket

as an OEM Carrier furnace part

As a furnace safety switch

depending on the specific appliance BTU rating

McDonnell & Miller 312700 Body Gasket While the 3155 series typicallyFor contractors servicing steam and hot water boilers, the McDonnell & Miller 312700 Body Gasket (Model 37 26) is a critical OEM component required to maintain the pressure tight integrity of 47 Series mechanical water feeders. This eight hole gasket is specifically engineered for use with the Series 47 2 combination water feeder and low water cut off units, as well as the 247 and 247 2 models. Over time, heat cycles and chemical exposure degrade the