Mark Controls Corporation

Wesley L Taylor

Harold P Adams

Warren R McNabb

James B Blanchard

A comparator for selecting from two air sources, air which requires less energy to condition includes a humidity and a temperature sections for comparing relative humidities and dry-bulb temperatures of air from each of the sources. Each section comprises two chambers separated from each other by a diaphram which is displaceable in the direction of the chamber having a lower pressure. A temperature post is attached to the diaphram of the temperature section and a humidity post is attached to the diaphram of the humidity section. The pressure in each of the chambers is determined by the pressure signal generated by a transmitter and it indicates the sensed condition. The post of the humidity section coacts with the post of the temperature section to give an output signal indicating which of the two air sources has a lower enthalpy except that when the humidity of the outside air is lower than that of the return air. In that instance, the temperature section alone determines the output signal. The output signal is either high or low. When the temperature post closes off a nozzle having supply pressure therein the output signal is high. When on the other hand, the temperature post is not closing said nozzle the output signal is low. The output signal is used to select air from the two air sources.

Comparator

An improved thermostat having two modes of operation selected by a pressure signal from a central source, which includes a separate set point for each mode of operation. Each set point has a scale which is clearly visible without removal of any parts of the thermostat. Each set point is also adjustable either by an adjuster that can be operated by occupants or only by authorized personnel having a tool fitting the opening in the set point adjustor. Adjustors can be provided with restrictors which limit set point adjustment to a predetermined range of temperatures and which can be adjustable by authorized personnel, or can be factory set.

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Glenview, IL, United States of America

Wesley L Taylor