Which of the following is NOT a distribution type for combustion appliances?

Radiant distribution is not typically classified as a distribution type for combustion appliances. The primary distribution types for these appliances usually involve mechanisms that effectively move heated air or water from the appliance to the spaces being heated.

Hydronic distribution refers to systems that use water heated by a boiler to transfer heat via pipes to radiators or other heat exchangers. Gravity systems rely on the natural movement of heated air, which rises and circulates due to convection. Forced air systems utilize a fan or blower to push heated air through ductwork into various spaces.

In contrast, radiant distribution is often considered a method of delivering heat rather than a specific distribution type for combustion appliances. It usually involves surfaces like radiators or heated floors that transfer heat directly to occupants and objects in the room without using a conventional appliance to distribute the heat through air or water systems. Thus, it doesn’t conform to the traditional definitions of combustion appliance distribution methods.