Fuel-fired heating appliance with temperature-based fuel shutoff system

Fuel-fired heating apparatus comprising:

• a combustion chamber thermally communicatable with a fluid to be heated;
• a burner structure disposed within said combustion chamber;
• a fuel valve coupled to said burner structure for supplying fuel thereto;
• an electrical circuit in which said fuel valve is connected, said electrical circuit being openable to prevent said fuel valve from supplying fuel to said burner structure;
• and
• a temperature sensing structure operative to sense a temperature within said combustion chamber and responsively open said electrical circuit in response to said temperature reaching a level correlated to and indicative of a predetermined, undesirably high concentration of carbon monoxide present in said combustion chamber,
• said temperature sensing structure including a normally closed switch disposed externally of said combustion chamber and connected in series with said fuel valve in said electrical circuit, said switch being openable, to thereby open said electrical circuit, in response to said temperature within said combustion chamber reaching said level,
• said temperature sensing structure having a portion projecting into said combustion chamber, defining a portion of said switch and being movable relative to the balance of said switch, in a manner opening said switch, in response to said temperature within said combustion chamber reaching said level.