GB526986A - Improved thermal control devices for automatic temperature regulation - Google Patents

Abstract

526,986. Automatic control systems for heating installations. LANDIS & GYR AKT.-GES. March 30, 1939, No. 10006. Convention date, Jan. 17. [Class 38 (iv)] Temperature.-Restoration of a thermostat controlling a heating installation is obtained without hunting by varying, in dependence upon the operation of the thermostat, the effect of an associated heating coil. Thermostat B associated with a flow pipe 1 comprises a bimetallic strip 11 and contacts 12, 13 arranged to energize either of motors 4 or 5 to rotate a valve 2 in the desired direction. An external thermostat A provided with a heating coil 8 connected through contact 7 to the power supply 9, 10 operates intermittently to provide pulses of current through a heating coil 19 of thermostat B. When conditions are stable the mean heating effect of coil 19 is such that the movable contact of member 11 remains in the mid position. If, due to an increase in temperature of pipe 1 or an increase in the mean heating effect of coil 19 caused by a rise in the temperature affecting thermostat A, contact 12 is closed and motor 4 and relay 14 are energized. Motor 4 rotates valve 2, through reduction gearing, towards the closed position and the contact 16 of relay 14 open-circuits resistance 21 in series with the heating coil 19. This causes a reduction in the heating effect of the coil 19 on an accelerated return of thermostat B. If the temperature change is in the reverse direction contact 13 closes to energize motor 5 to open valve 2 and also energize relay 15 to short-circuit resistance 20 over contacts 17. The resultant increased heat output of coil 19 causes the element 11 of the thermostat to return quickly to its mid position. In a modified arrangement, Fig. 2 (not shown), the thermostat A is not employed and the main thermostat is placed in the space whose temperature is to be controlled ; its heating coil being connected directly to the supply.