Air-conditioning system

Claim 1

A heating and cooling unit for an air conditioned space comprising: (a) air heating and cooling means; (b) an air blower for directing air from the space into heat exchange relationship with the heating and cooling means; (c) a return air passage through which air from the space flows to the heating and cooling means; (d) a discharge passage through which the air is discharged to the space; and, (e) a control for governing operation of the heating and cooling means at least in part as a function of sensed air temperatures comprising: (i) a thermostatic actuator having an expansible and contractible bellows defining a chamber communicating with first and second fixed volume bulbs via capillary tubing, said bulb, chamber and capillary tubing filled with a thermally expansible and contractible liquid, one bulb disposed in heat transfer relationship with air which flows through said air return passage and a second bulb disposed in heat exchange relationship with air which flows through said discharge passage, said first bulb defining a substantially larger volume than said second bulb, and said bellows chamber volume determined by the heat content of said liquid; (ii) a linkage member moved in response to expansion and contraction of said bellows with the linkage member position determined by the heat content of the fill liquid as reflected by expansion or contraction of said bellows volume; (iii) a cooling control switch means having a first condition in which cooling of the air is effected and a second condition in which cooling of the air is terminated, said cooling control switch means operated to said first condition in response to a linkage member position indicative of a first heat content of said liquid and operated to said second condition in response to a linkage member position indicative of a second heat content of said liquid which is less than the first heat content; and (iv) a heating control switch means having a first condition in which air heating is initiated and a second condition in which air heating is terminated, said heating control switch means operated to said first condition in response to said linkage member being positioned at a location indicative of a third heat content of said liquid and operated to said second condition in response to a linkage member position indicative of a fourth heat content of said liquid greater than said third heat content and less than said first heat content.