Abstract: A control mechanism for a gas-fired hot water heater, which operates without a permanent burner pilot, has an electrical circuit for selectively operating an igniter in response to gas pressure in the heating system. The water heater has a main chamber for providing gas to the igniter pilot and the burner element, and a secondary chamber for providing gas to a safety pilot. Circuitry responsive to a high gas pressure in the main chamber activates the igniter and circuitry responsive to a high gas pressure in the secondary chamber interrupts operation of the igniter. Continuous operation of the igniter element is thereby prevented, for example, due to a low gas pressure condition.

Abstract: An apparatus for heating water with solar radiation incorporates an auxiliary heating unit, external to the hot water reservoir and bypassing the solar heating element, for providing auxiliary water heating whenever the temperature in a selected portion of the reservoir decreases below a predetermined level. A common return conduit in combination with a single supply pump and a selector valve enable the auxiliary heating "by-pass" circuit to be simply and quickly added to already existing installations.

Abstract: The fail-safe gas valve solenoid construction disclosed herein employs a fixed electromagnet which, when energized, actuates an operating rod by means of an armature which is relatively loosely secured to the shaft to permit self-alignment between the magnet and the armature. Relative movement and wear between the armature and the shaft is inhibited by an elastomeric washer or O-ring which is interposed between the armature and a corresponding or facing surface associated with the shaft, the washer being under slight compression.

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.