GB591458A - Automatic system for controlling the temperature of a space - Google Patents

Abstract

591,458. Automatic control systems. VAPOR CAR HEATING CO., Inc. Aug. 16, 1944, No. 15634. Convention date, Aug. 9, 1943. [Class 38 (iv)] Temperature.-A thermostat, responsive to a space temperature subject to automatic control by mechanism adjusted at upper and lower temperature limits of a temperature range, has an auxiliary electric heater and means to vary the heating current to change the effective relation between the temperature range and the temperature of the space without change in the range. A mercury column control thermostat 17, Fig. 1, has contacts 29, 30 respectively causing the opening of a relay 18 and the closing of a relay 19. These relays when closed energize a reversible motor 15 in series which increase and decrease respectively the heat applied to the space in which the thermostat 17 is installed. The range of temperature between contacting at 29 and 30 is fixed by the construction of the thermostat but current supplied to a heating winding 27 may be varied to change both effective temperatures equally by adjusting a series resistance 23 or a shunt resistance 21. When relay 18 operates by contact at 29 a resistance 20 is connected in parallel with resistance 21 to increase the heating of coil 27 and when relay 19 is operated by closure .at contact 30 all auxiliary heat is removed by opening of the back contact of this relay and intermittent action of the relays and motor 15 results. Fig. 1 shows a master thermostat 16 also subject to the space temperature. This thermostat has an auxiliary-heater and a contact 25 adapted to place a resistance 22 in shunt with its heater and causes intermittent closure at contact 25. The heating circuits of both thermostats are in series so that the master thermostat adjusts the mercury in the control thermostat except when above contact 30 and below contact 29 while the control thermostat adjusts the mercury in the master thermostat. Fig. 1 shows the motor 15 adjusting a damper 14 determining the relative proportions of cooled and heated air directed into a space. Figs. 2 and 3 (not shown) relate to the application of the invention to the control of a damper regulating the flow of air through a casing surrounding a cooling coil in an oil circulating system associated with an engine crank case, the master and control thermostats being responsive to the temperature in the circulating pipe. The higher temperatures involved necessitate higher currents in the auxiliary thermostat heaters and a relay is interposed in the heater circuits to present destructive sparking at the upper contacts of the thermostats. Fig. 4 (not shown) illustrates a modification of the system of Fig. 1 having no master thermostat.