GB1193711A - Improvements in or relating to the Control of Thermal Conditioning Systems - Google Patents

Abstract

1,193,711. Automatic temperature control systems. HONEYWELL Ltd. Feb. 16, 1968 [Feb. 24, 1967], No. 9080/67. Heading G3R. A system for heating or cooling providing a temperature in a space at a predetermined time comprises a timer for generating a set point signal which progressively approach a value representative of a determined temperature throughout an interval immediately preceding the determined time which signal is modified by a second signal representative of thermal conditions outside the space and means for comparing the modified set point signal with a signal representative of space temperature and producing an output signal when a comparison indicates two are equal, such output signal initiating operation of the system. The desired temperature at various periods during a day is represented by a dotted curve AJCD and the actual room temperature by a solid line curve ABCD. When the room temperature drops during say the night to point B the system cycles at this low temperature until point C is reached when a gradually increasing set point signal actuates a heating system so that at some determined time say 9 a. m. the determined temperature is reached in the room. The set point signal is derived from a resistor (8) Fig. 3 (not shown) which is positioned by a cam driven by a timing motor (9) the resistor forming one arm of a bridge circuit (2). A further bridge circuit includes an outside temperature sensor which modifies the set point signal so that it may follow, for example a dotted curve HD. When the outside temperature is higher as in these conditions the heat losses are smaller the room temperature may fall along a curve AE and heating will commence after point in time at E. The bridge circuit through an amplifier may operate a relay controlling a boiler and circulating pump but other types of heating systems e.g. ducted air with an electrical, oil fired or a gas fired source are envisaged. The system is also applicable to off peak electric storage heating systems in which the final temperature D may be arranged to be above a normal comfort zone as further energy is not available after the end of such off peak period. Switch on of such heaters is arranged to be earlier when the outside temperature is low. The signals may be represented by pneumatic as liquid pressure signals. During the day, the temperature may be maintained at a set value DA by thermostatic means (not shown) and the set point driven to a higher value HL than this by suitably shaping the cam.