GB644129A - Temperature control apparatus - Google Patents

Abstract

644,129. Automatic temperature-control systems. VAPOR HEATING CORPORATION. June 12, 1947, No. 15554. Convention date, June 15, 1946. [Class 38 (iv)] In a temperature-control apparatus employing two thermostats E and F, controlling the temperature of a space D between upper and lower limits respectively, each has an auxiliary heater G, H, the energization circuit to the heater G being broken by the action of either thermostat whereas the circuit to the heater H is continuously energized, the heating current thereto being increased upon de-energization of the heater G. The thermostat E is arranged so that above a predetermined temperature a relay El is de-energized so as to complete a circuit to the field winding 14 of a motor K causing it to operate in a sense to close a valve 10 controlling a supply of hot air. At the same time the energizing circuit of the auxiliary heater G is broken so that the temperature of the thermostat falls and the current previously passing through the heater G is transferred to the heater H to ensure that the contacts of the thermostat F remain closed and that the relay F<SP>1</SP> remains de-energized. Consequently a step-by-step control is effected by means of the thermostat E. When the temperature falls to a value such that the heater G is no longer able to cause deenergization of the relay E<SP>1</SP>, the contacts of thermostat F break, causing energization of a relay F<SP>1</SP> and consequent energization of the motor K in the reverse direction to open the valve 10. Energization of the relay F<SP>1</SP> causes the heater G to be de-energized and the main circuit of the heater H to be completed so that the temperature of the thermostat rises. A further step-by-step control is thus obtained by means of the thermostat F until the additional heat of the heater H is no longer required to cause closure of the thermostat contacts. The temperature control is then passed back to the thermostat E. Both auxiliary heaters have a supply circuit through a variable resistance I, equal amounts of current being supplied to both heaters. When, however, the circuit to heater G is broken the full current is supplied to heater H. If the supply of hot air is insufficient to heat the space D to the required temperature an auxiliary heating device C is switched on by operation of a limit switch 34 when the valve 10 is fully open. Also energization of a further motor L controlling a supply of cool air is effected by a limit switch 27 when the valve 10 is fully closed, if the temperature of the space D is above that required.