You are installing a listed warm air upflow furnace in a residence. The furnace has a limit control that is factory set for 250 degrees. The room is large in comparison to the furnace. What is the minimum clearance betw een the sides of the supply air plenum and the combustible walls of the room where the furnace is to be installed?

You are installing a listed warm air upflow furnace in a residence. The furnace has a limit control that is factory set for 250 degrees. The room is large in comparison to the furnace. What is the minimum clearance betw een the sides of the supply air plenum and the combustible walls of the room where the furnace is to be installed?