Heating systems – Automatic control – Water
Patent
1995-11-20
1998-09-01
Ford, John K.
Heating systems
Automatic control
Water
237 123B, 236 78D, 364162, 165269, F24D 300
Patent
active
057998698
ABSTRACT:
Apparatus for heating and cooling an enclosed operator space in an off-road vehicle controlling evaporator fan speed, compressor clutch and condenser fan operation, and having sensors for detecting operator space temperature and an evaporator freezing condition, the condenser fan motor fuse condition, and under or over pressure conditions in the compressor; the apparatus also controls the operation of a heat source such as a heat valve in a coolant path or an electric resistance heater. The evaporator fan speed is controlled by pulse-width modulating power to the fan motor and speed is displayed by a bar graph; a digital display of temperature and system diagnostics is also provided. Operation of the clutch is inhibited when the evaporator freezes. The apparatus includes an electronic temperature control circuit which has a first, narrow deadband within which actual temperature variations are ignored, and a second, wider deadband within which temperature variations must exist for a preset period of time before the apparatus will shift between COOL and HEAT modes.
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Shrakar, Mini & Microcumputer Control in Industrial Processes 1980 Tp 155.75 M53 (Copy in 236/78 d) pp. 82-83.
Fishbeck, Writing PID Control Loops Easily in Basic Control Engineering vol. 25 No. 10 pp. 45-47 Oct. 1978.
Eagle Engineering and Manufacturing, Inc.
Ford John K.
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