Abstract: An electric resistance humidifier which increases atmospheric humidity by boiling water in a tank. Spaced conductive plates, or electrodes, are fixed in the tank. As the tank water level rises, the immersed area of the electrodes increases. An electric supply causes the electrodes to pass electric current through the tank water therebetween for heating and vaporizing such water. Electric current and heating cease automatically when the tank water level falls below the electrodes. A control includes comparator circuitry responsive to a reference signal and a signal related to electrode current for actuating and deactuating a water supply to the tank. In one embodiment, the control includes further comparator circuitry responsive to electrode current and a further reference signal for controlling a tank drain, to compensate for rising conductivity of the tank water as it warms toward boil and thus prevent substantial overshoot in heating current flow.

Abstract: In an air conditioning system for selectably heating and cooling an enclosed space under control of a room thermostat, dew point temperature of ambient air in the space is maintained below a preselected maximum value by modified use of the heating and cooling apparatus without separate humidity control. For this purpose the cooling apparatus is controlled by a sensor responsive to absolute moisture content in parallel with the normal thermostat control. Energy is further conserved by night set-back of the thermostat with cooling apparatus normally disabled in night set-back.

Abstract: A method and apparatus for providing temperature and humidity controlled air to an enclosed space within a building to achieve desired conditions of temperature and humidity therein, and which is characterized by the maximum use of the outside air for cooling purposes to thereby minimize the load on the refrigeration unit and thus also minimize the operating expense thereof.

Abstract: A humidity controller includes a set point device, which establishes a set point for humidity within a given area, and a humidity sensor, which senses the humidity within the area, connected in a sensing network which provides a differential output voltage indicating deviations of the humidity from the set point. The output voltage selectively enables differential threshold detecting circuits which energize humidifying and dehumidifying apparatus to return the humidity to the set point value. A differential range adjust, which establishes a turnon threshold for the detecting circuits, is derived from the set point such that the turnon differential for the detecting circuits remains fixed regardless of the set point value.

Abstract: An air quality sensing apparatus for measuring, monitoring and controlling temperature and air relative humidity of air interior a room, including an apertured housing enclosing temperature and humidity sensing devices and an asperating tube fluidly interconnecting the interior of the housing and a return air system.

Abstract: A fluid control system being responsive to humidity conditions as sensed by a humidity responsive control device that controls a fluid bleed means of the control system in response to humidity conditions sensed thereby, the humidity responsive control device having a flapper spring lever pivotally carried by a frame in a cantilevered manner and having a free end controlling a bleed valve seat. The flapper spring lever has a normal bias to tend to move the flapper end to one of its pivoted positions relative to the valve seat and is operatively associated with an actuating lever by a spring means, the actuating lever being controlled by a humidity sensing means.