Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: An improved flue pipe construction particularly adapted for a fuel fired water heater is disclosed which serves to reduce or minimize heat loss when the water heater is in a standby mode. The flue pipe construction comprises inner and outer concentric flue pipes which define an air space therebetween and one or more valve arrangements associated therewith to selectively restrict air flow through such air space. The valve arrangements include a thermally responsive actuator operative to open and close the valve member in response to heat generated by firing of the burner assembly without the need for any external power supply or interlocks.

Abstract: An improved flue pipe construction particularly adapted for a fuel fired water heater is disclosed which serves to reduce or minimize heat loss when the water heater is in a standby mode. The flue pipe construction comprises inner and outer concentric flue pipes which define an air space therebetween and one or more valve arrangements associated therewith to selectively restrict air flow through such air space. The valve arrangements include a thermally responsive actuator operative to open and close the valve member in response to heat generated by firing of the burner assembly without the need for any external power supply or interlocks.