Abstract: A controller, for controlling an electrode boiler steam humidifier includes a plurality of current loop transformers, coupled to the boiler electrodes, for sensing the current drawn by the electrode boiler. A current level detector provides a control voltage to a solenoid controlled valve, associated with the boiler, to drain a predetermined quantity of water from the boiler and thereby reduce the electrode current, when the electrode current exceeds a predetermined upper current limit. A resettable counter is provided for limiting the number of automatic attempts which can be made to reduce the electrode current. Normal periodic actuation of the humidistat resets the counter to avoid reaching the predetermined count through long-term acquisition of isolated over-current occurrences.

Abstract: A controller for controlling an electrode boiler steam humidifier, of the type operable from a source of polyphase alternating current, is provided. A plurality of current loop transformers, coupled to the boiler electrodes, sense the individual currents drawn in each phase of the polyphase alternating current. A plurality of full-wave bridge rectifiers individually couple the secondaries of the current lube transformers to the input of a voltage amplifier such that the output of the amplifier is indicative of the highest of the currents sensed in each phase of the boiler electrode current. When the output of the voltage amplifier exceeds a predetermined threshold, a control effect is produced such that operation of the humidifier is controlled in accordance with the highest of the individual phase currents drawn through each of the boiler electrodes.

Abstract: An electronic control for positioning the damper in the air supply duct of a variable air volume system having a motor to open and close the damper, a thermostat circuit sensing temperature in a conditioned space and developing a voltage signal indicative of the temperature in the space relative to the thermostat setting, an electronic air flow sensing circuit sensing air flow into the conditioned space and developing a voltage signal indicative of air velocity, a circuit processes both signals and applies the difference between them to an electronic variable timer which effectively varies the motor speed (by varying the motor duty cycle) so said damper is moved slower as equilibrium between the space temperature and the set point of the thermostat is approached. The same voltage signals are fed into a logic circuit to determine the direction of motor rotation to determine whether the damper opens or closes.