Abstract: A blower draws air through an inlet duct from outside a building or dwelling and injects air and fuel into a sealed combustion chamber where they are ignited and burned within a ceramic crucible within combustion chamber. The pressurized combustion gases flow up an exhaust stack in the water tank of the water heater. The exhaust stack is connected to a vent that extends through a building outside wall. The vent is surrounded by the inlet duct which has an opening spaced from the outlet vent so that air from the vent is not captured by the inlet. The combustion chamber and the heat exchanger are sealed from the interior of the building and both the air inlet to the blower and the air outlet from the heat exchanger freely communicate to the outside of the building. A timer within the controller operates the blower for a period of time after the fuel supply to the burner has been shut off.

Abstract: Welding apparatus particularly adapted for use in welding parts into the interior surfaces of a metal tube in a pre-determined pattern obtained by longitudinal and rotational indexing of the tube. An elongated electrode arm, which is selectively flexible in one direction, extends into the tube and has a feed track attached thereto through which the metal pieces to be welded are moved into position to the welding head on the end of the electrode arm. The other end of the electrode arm is rigidly connected to a mount and is electrically insulated therefrom. A hydraulic piston carried by the electrode arm at its free end is actuatable to drive the entire arm sideways in its direction of flexibility so as to bring the piece to be welded into firm contact with the inside of the tube. Electrical current is then passed through the electrode arm and the piece to be welded, to the tube, and then to a grounded contact, to resistance weld the metal piece to the tube.