Patent GB-645472-A (GB)
Title: Weighted average temperature control
IPC: F24D19/10
Filed: 1946-03-07
Abstract: 645,472. Automatic air temperature control systems. VAPOR HEATING CORPORATION. March 7, 1946, No. 7205. Convention date, April 16, 1945. [Class 38 (iv)] A thermostat controlling the air entering a space has an auxiliary heating winding which is closed by the thermostat controlling the temperature of the air within the space. General description.-The invention is des. cribed as applied to a railway carriage having two rows of compartments, A, in Fig. 1. Each compartment is heated by an individual steam radiator C, while all the compartments are traversed by a current of temperature controlled air. The radiators Care each controlled by an individual thermostat G inside the compartment, the datum of which is manually selectable, while the air stream temperature is a function of the temperature condition of all the compartments. An external thermostat V, interrupts the supply to all the radiators C when the external temperature is above 50  F. All thermostats are of the mercury column type and the system is changed from the " standby " to the " in-service " condition by means of the manual switch M6. Compartment temperature control.-A thermostat G, Fig. 6, is adapted to short-circuit relay winding 15 when the temperature reaches a predetermined value. De-energization of relay 15 energizes relay E to close the steam valve D of the radiator C. The thermostat G is affected both by the ambient temperature and the heating winding 18, the current in which can be adjusted by a variable resistance 37, to vary the operating temperature of the relay 15. When relay 15 is energized, winding 18 is also supplied over resistance 58, so that relay 15 is de-energized when the ambient temperature is below the setting of 37, the current supplied over resistance 58 thereupon ceases, and thermostat G being effected to operate at a lower level, it thereupon energizes relay 15 again ; this intermittent operation continues until the ambient temperature corresponds to the setting of 37 and precludes the ambient temperature rising above the setting of 37. A switch 39 permits the replacement of the variable resistances 37 by fixed resistances whereby all compartments may be operated at the same temperature. Control of temperature of circulated air.-Air is circulated from a blower L, Figs. 1, 2 through coolers S, S<SP>1</SP> and heaters K, K<SP>1</SP> to ducts H, I from which it flows through grilles J, into the compartments A and through the grilles J<SP>2</SP>, through the return duct to the blower. Thermostats O, O<SP>1</SP> in the supply ducts H, I control the operation of the heaters K, K<SP>1</SP> while thermostats R, R<SP>1</SP>, Fig. 6, in the return duct control the coolers S, S<SP>1</SP>. Thermostats O, O<SP>1</SP> have their heating windings 24, 24<SP>1</SP> supplied over contacts 30 of relay 28, resistances 76 and contacts of relay 15, so that as relays 15 de-energize (i.e. as each compartment reaches its datum temperature) the associated resistance 76 raises the current through the windings 24, 241 and the level at which the heaters K, K<SP>1</SP> are switched off is lowered. Similarly, the thermostats R, R<SP>1</SP> in the return duct, and controlling the coolers S, S<SP>1</SP> have their heating windings put in circuit with resistances 76 so that as the compartments are satisfied the level at which the coolers are switched on is reduced until when thermostats R, R<SP>1</SP> make contact with electrodes 23, 23<SP>1</SP> relays 21, 21<SP>1</SP> are operated to switch on the coolers. Relays 21, 21<SP>1</SP> also supply additional current to windings 22, 22<SP>1</SP> and 24, 24<SP>1</SP> of thermostats R, R1, O, O<SP>1</SP> so that a rapid contraction of the mercury therein is avoided. If thermostats R, R<SP>1</SP> make contact with electrodes 25, 25<SP>1</SP>, relays 20, 20<SP>1</SP> are de-energized to switch out the heaters K, K<SP>1</SP>. Thermostats 0, O<SP>1</SP>, R, R<SP>1</SP> when operated supply their heating windings with additional current, so that, as for thermostats G, they open and close intermittently until the temperature in their vicinity corresponds to the temperature at which they should operate, to prevent overshooting. Operation when car is waiting to enter service.-Manually operated switches M1, M2, M3, M5, Fig. 6, are opened, switch M6 is closed so that the external thermostat V, is connected to control relay 19 which controls relay 19a operating the main steam valve 20a, Fig. 1. Switch M5 is opened to de-energize the relays E to open the compartment steam valves D. Thus the main steam valve 20a is closed when the external temperature exceeds 50 F. Operation when car is,put into service.-Switch M1 is closed to start the blower motor M ; switch M5 is closed to place the compartment radiators under the control of the compartment thermostats, switch M2 is closed to energize relays 20, 20<SP>1</SP> so that their de-energization is under the control of thermostats O, O<SP>1</SP> in the supply ducts H, I, Fig. 1. Operation when external temperature rises above 50 F.-External thermostat V deenergizes relay 19 and relay 19a is energized to close the main steam valve 20a, if relays 20, 20<SP>1</SP> are energized. Contacts 78, 84 close and a circuit is completed to contact 81 of thermal switch R. With the car temperature sufficient to cause the mercury column of switch R to engage the contact 23 and with a predetermined number of room thermostats G satisfied and therefore supplying current to heater 22 through resistors 76, the cooler S is operated, in addition to the heater K, the duct air being first cooled in S and then passed through the heater K. With the mercury bridging the contacts 81, 23 of switch R, relay Y closes and thereupon : (1) compressor motor 89 is started ; (2) cooled inlet valve is opened ; (3) additional current is supplied to heater coil 22 of thermal switch R to prevent a large contraction of the mercury column unless a large drop of car temperature occurs. When the mercury column of switch R engages the contact 25, solenoid 20 of relay M is short-circuited to de.-energize relay P and thereby render radiator K inopera. tive. Cooled air is therefore only delivered to the room A. Wattage control.-In order to maintain the settings of all thermostats fixed, in the event of a fluctuation of the supply voltage, all thermostat heating windings are connected in series with the contacts 31 of a relay 28 which is controlled by a thermostat the heater 27 of which is supplied directly from the mains and the mercury column of which normally is maintained close to the outer contact. In a modification (not shown), two thermal switches R are employed in parallel on a low voltage system and the auxiliary heaters for these and the thermometer O are connected in parallel. Specification 645,536 is referred to.