Patent GB-478415-A (GB)
Title: Improvements in temperature control systems
IPC: F24D19/10
Filed: 1937-06-25
Abstract: 478,415. Automatic control systems. VAPOR CAR HEATING CO., Inc. June 25, 1937, No. 17755. Convention date, June 25, 1936. [Class 38 (iv)] Temperature.-Heating means B and cooling means C are automatically controlled by thermostatic means N, within a space to maintain the temperature within that space substantially constant so long as outside temperature lies within certain limits, but when these are exceeded thermostatic means M subject to outside temperature brings into action thermostats H, L, also within the space to step up the inside temperature as the outside temperature falls below or rises above those limits. The system described comprises a fan 5 circulating air past the heater B and cooler C into a space defined by walls 1 having outlets 2 for exhausting a portion of the air and means for withdrawing air past a thermostat L ; make-up air from outside passes over a thermostat M which, within the limits of temperature referred to, connects a supply conductor 14 to the contacts 94 and 111 of the two thermostats N. These control respectively a heating winding 30 of a thermal switch G controlling a valve D for supplying heating medium and a heating winding 57 modifying the action of a thermostat L controlling, through a relay K, a valve J in the supply of cooling medium. While the outside temperature remains in this intermediate zone a rise of inside temperature will close at contact 111 the circuit of the heater 57 ; the thermostat L is thus caused to energize the relay K and the valve J is opened to effect cooling. Should the inside temperature fall the circuit of the heater 30 will be opened at contact 94 whereupon the switch G will energize the valve D to admit heating fluid. The thermostats N thus maintain inside temperature within certain limits by selective intermittent control of the valves J, D. When the outside temperature rises beyond the intermediate zone the thermostat M disconnects the circuits through the contacts 94, 111 and the thermostats N become ineffective. The supply conductor 14 is connected instead to the heater 30 direct whereby the valve D supplying heating fluid is maintained closed and the heating winding 57 is fully energized so that the thermostat L will be effective to control the valve J so as to prevent the inside temperature from rising beyond the upper limit; as the outside temperature continues to rise however, resistances 78 are progressively inserted in series with the heating winding 57 and the limit of inside temperature thus rises progressively also. As the outside temperature falls below the intermediate zone the thermostats N are rendered ineffective as before by the thermostat M but the circuit of a heating winding 40 on the thermostat M is fully energized to cause this thermostat to permit such operation of the relay F and valve D as will maintain an inside temperature somewhat above that existing in the intermediate zone of outside temperature. Progressive decrease of outside temperature will insert resistances 68, 69 in circuit with the heater 40 to cause progressive increases in the inside temperature limit.