According to the Code, any unlisted residential type boiler water heater, or furnace shall have a minimum clearance on the back and sides of not less than ____ inches unless a form of protection specified in the code is used.

According to the Code, any unlisted residential type boiler water heater, or furnace shall have a minimum clearance on the back and sides of not less than ____ inches unless a form of protection specified in the code is used.