Abstract: An exhaust system for withdrawing a supply of exhaust gases from an exhaust flue of a heater and expelling the exhaust gases to atmosphere at a remote location that includes a mixing tee for mixing a flow of dilution air and a flow of exhaust gases. The mixing tee includes a first end coupled to the inlet opening of a blower housing and a second end coupled to a supply of dilution air. The dilution air inlet pipe of the mixing tee extends along a longitudinal axis. The mixing tee includes a flue pipe having a first end positioned to receive the exhaust gases from the heater and a second end that enters into the dilution air inlet pipe. The flue pipe extends along a longitudinal axis that is positioned at an angle relative to the longitudinal axis of the dilution air inlet pipe. The exhaust flue extends toward the upstream end of the dilution air inlet pipe such that the flow of dilution air impinges upon the flow of exhaust gases.

Abstract: An instantaneous demand gas fired hot water heater apparatus having the water temperature sensing thermostat disposed in the upper hot water outlet header with the inlet flow of unheated water directed to flow in a preferred flow path across the temperature sensing element. The temperature sensing element location in the upper header of the heater provides an extremely sensitive and efficient burner control. Upon initial output demand of hot water the lower temperature of the unheated water is immediately sensed by the temperature sensing element to immediately commence burner operation. Upon termination of heater water demand, the heated water temperature is rapidly sensed by the temperature sensing element to promptly terminate the supply of the gas to the burner and minimize unnecessary heating of the water.

Abstract: In a water tube boiler comprising a housing enclosing tubes bent to form vertical chambers successively traversed by rising hot combustion gases, the tubes being connected at the bottom to the interior of the jacket of a jacketed cylindrical combustion chamber, which jacket is supplied with cold water, and at the top to a steam manifold, the manifold and jacketed chamber project beyond the housing with a downcomer outside the housing connecting the top of the jacket and the lowest part of the manifold, thereby permitting the boiler to operate with a shallow level of water in the manifold, speeding up circulation of water and its heating, and permitting substantially dry steam to be discharged from the upper manifold. The chambers may include baffles which are angled so that the hot gas hits them at an angle less than 90.degree. so as to be deflected thereby in the direction of its advance, thereby avoiding hot spots.