CH-boiler control

If you still alter your central heating system"s boiler thermostat according to the season (many people nowadays leave it at the same — fairly high - setting throughout the year), this may cause the boiler to be switched on and off too frequently when the weather is unseasonly cold (see figure la). This problem may be resolved by the pres- ent circuit which prevents the boiler being switched on for some time, td, after the switch-off temperature, T2, has been reached. After tdhas lapsed, the boiler temperature, T, should have dropped well below the switch-on temperature, T, (see figure lb). The circuit in figure 2 is an extension of the central heating monitor (Elektor, July/August 1984, p. 7-30) and formed part of the electronic gas meter (Elektor, November 1984, p. 11-59). The make contacts of a relay 7-28 CH boiler control la elektor july/august 1985 lb quent change of logic level at the out- put selected by Si causes the reset of the bistable via N 4. This is the end of td...