Fuel-fired heating appliance having flame arrestor plate with associated scale deflector shield

The present invention generally relates to fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly provides a gas-fired water heater having a combustion chamber bottom wall portion defined by a perforated flame arrestor plate with which an overlying scale deflector shield structure is operatively associated. A fuel-fired heating appliance, representatively a gas-fired water heater, has a combustion chamber with a flame arrestor plate forming a bottom wall thereof. The arrestor plate has a spaced series of flame quenching perforations therein through which combustion air upwardly flows into the combustion chamber during firing of the water heater. A shield structure within the combustion chamber overlies the arrestor plate perforations in an upwardly spaced relationship therewith and blocks operating scale on the bottom side of the top combustion chamber wall, and/or a flue extending upwardly from the top combustion chamber wall, from falling on and blocking the combustion air transfer perforations in the flame arrestor plate.