Document 6R0XdaKr3Lw3axRoaer6bVe4E

American Society of Heating and Ventilating Engineers Guide ujjj' --Ml perature of the air introduced to the ventilated spaces will fa\[ . falling temperature reaches the temperature for which the multiple thermostat is set, this thermostat will then begin to function and nf steam to enter the heaters so that the temperature of the air introPdermit will be prevented from continuing to fall, below the minimum des"ui ced point. The fan discharge thermostat, therefore, functions as a mi.n'i'rahlf temperature control and prevents the introduction of air at temp"earnai'mal which would produce drafts and faulty distribution. Very accurateatmel trol of room temperatures is accomplished by this arrangement, sinceth direct radiation serves as a heating effect and the air introduced s degrees below room temperature furnishes the necessary coolingseveral to prevent overheating. effect: Chapter 20--Automatic Heat and Humidity Control position of the valve under control. In hot water heating syscsiKotieor example; the water temperature may be maintained in proigon to the outdoor temperature. This type of control may be applied f(esttowkaetresroarntdo sdteisatmrichtesatetianmg ssyysstteemmss,. and to gas burners, oil burners' (^gch C.onctroonl trol of steam valves has been found to assist in efficient wJ-^tion 0f the heating plant. Centrally-located,, manually-operated S0^es are used in this connection to operate valves in steam risers or jjnes feeding certain sections of the building. Outdoor air, vent `Y S3 YS&/S&/S/S////A ^J?2h?//^/7////7777k Fig. 11. Use of Pilot Thermostat with Ventilating System Two-Temperature Control This is used when it is desired to control at two distinct temperatures by means of a single instrument. For example, a temperature of approxi mately 70 F may be desired during the day, while some lower temperature is satisfactory during the night. Shifting from the high to the low tem perature may be accomplishedEither at the thermostat or at some remote point by means of a switch. Weather-Compensating Control ` Weather-compensating thermostats have been developed for controlling the temperature of the heating medium with respect to the outdoor tem perature. This type of control makes use of two liquid-filled bulbs con nected by means of capillary tubing to a common Bourdon tube which operates a mercury tube switch. This switch opens and closes an electric circuit, which in turn operates a motorized valve. One bulb is placed outdoors and the other is attached to a riser near the boiler. Expansion of the liquid in the bulb in contact with the riser moves the Bourdon tube to its off position and the outdoor temperature then determines the 310 .'Fig. 12. Electric Thermostat Applied to Oil Burner for Heating System Vand recirculating dampers in connection with ventilating systems may <f?o advantage be conveniently operated from some central point. ' RESIDENCES ..".In residence heating, the thermostats should be located in represen tative or key places; never, of course, on an outside wall or near a window, npr too close to radiators or in a drafty hallway. They should be located on-a wall of the room which has the greatest number of hours of occu pation, preferably .the living room. . Fig. 12 illustrates a hot water heating system with thermostatic control. ' Thermostat No. 1 asks for heat and gets it unless thermostat No. 2 (claiming the heating medium is already too hot, prevents it. Thermostat 3 will shut down everything regardless of No. 1 and No. 2, if once ,, having been warm it gets cold, indicating that the pilot flame is out; or J| following operation of the burner it does not get warm promptly, indicating that, ignition has failed. . >',/Fig. 13 illustrates a steam or vapor plant performing the dual service. . Either the room thermostat or the tank thermostat may cause the open- . 311