Automatic selector for central heating programme - uses temp. sensors on outside wall to control heating when selected by programme clocks on basis of threshold crossings

摘要

Three thermostats (A,B,C) are located on the North face of a building and their demand value temps. are set to different values e.g. 3,10,16 deg.C. These thermostats are connected to an assembly of three clocks (P1,2,3) for mid season, winter and and weekly control. The mid season clock is programmed by switching tabs and cams to initiate minor heating cuts while the winter clock initiates major heating cuts. The third clock is programmed to cut the heating during the weekends when the building is only occupied during the week. Thsee clocks switch a relay coil (R) into circuit to close contacts (1,2,3) to connect the thermostats into circuits. A manually operated switch (4) is connected in parallel with the relay contacts to provide protection against freezing. Negative logic is used for the relay coil to close the contact of the power is removed by a breakdown.