Abstract: An apparatus and process for preventing thermal shock caused by the introtion of steam into a superheater header by preheating the header with an electrical heating element located on the header before boiler light-off and the introduction of any steam. A temperature sensor located on the header controls the coupling of the heating element to its voltage source to maintain the temperature of the header within a predetermined range.

Abstract: A test circuit for use with a boiler control circuit. A test switch and a lamp are connected between ground and a water level electrode. In the presence of a water path, a sufficient potential drop exists between ground and the electrode to light the lamp when the test switch is closed. If a ground or short exists, the lamp will not light.

Abstract: The safety device disclosed herein is adapted for use with low power gas burning water heaters which are unvented. In order to limit the duty cycle of the heater, a thermal mass having a preselected thermal inertia is heated from the burner through a probe of limited heat conductivity so that the temperature of the thermal mass rises relatively slowly during operation of the heater and cools relatively slowly in the intervals between operation. If the thermal mass reaches a predetermined threshold temperature, the heater is turned off or sharply throttled back so as to limit the emission of combustion products into the atmosphere.

Abstract: A device for limiting the temperature and pressure of a fluid by controlling the electric current to a heating element. The device includes a cylinder connected with a tank in which the fluid is heated and includes a pressure responsive piston movable within a cylinder against a compression spring opposing movement of the piston. The piston is tapered to a conical or somewhat pointed shape at its lower end to allow a faster escape of fluid from the tank and to guide the piston into an opening in the tank to achieve a thorough seal when the pressure in the tank has been relieved. The cylinder has a discharge opening threaded externally to which is attached an internally threaded discharge pipe, the threading being such that the installer cannot jam the pipe against the piston and thus stop its movement. When the pressure exceeds that for which the spring is designed, the piston compresses the spring and operates an actuator for a microswitch to break the electric circuit to the heating element.

Abstract: A safety shut down warning assembly of the manual reset or recycling type installed at the lower section of a water heater storage vessel inside or outside the wall of the storage tank of the vessel to sense a predetermined increase in temperature above the normal operating temperature in the lower portion of the tank as the result of buildup of lime or other sediment in the bottom of the tank of the storage vessel. The sensing device is then activated by the increase in temperature to shut down the heating unit employed with the storage vessel to heat the water stored therein and/or turn on a warning light or other signal.