Central heating system circulation pump switching control - using counter indexed by shutting down pulses for mixer valve

摘要

The central heating system has a mixer valve (4) adjusted via a setting pulse supplied in dependence on the difference between the actual and required temps. The shutting down pulses are used to index a counter, reset by the opening up pulses, with the circulation pump (5) switched off when a predetermined count value is reached and switched back on again by the next opening up pulse. The burner for the central heating boiler (1) may be shut-down when the circulation pump (5) is switched off. Pref. a module N counter is used, having a divisi on factor of N, its reset gate receiving the opening up pulses via an OR gate. When the count reaches the full value the counting input is switched to the output to provide a continuous pulse, maintained until the counter is reset.