Load-shedding circuit e.g. switching off storage heater - has cross-branch connecting control contact in parallel with PTC, and self-latching contact with NTC resistances

摘要

A through-flow heater (1) has a load-shedding relay (2) whose winding (3) when energised holds a first control contact (4) open. Delay is introduced by a holding relay (5) with a self-latching contact (7) and a second control contact (8) which is wired to the three-pole relay (9,11) protecting the storage heater (14). Transient movements of the first control contact (4) are nullified by NTC and PTC resistance (15,16) in series with the self-latching contact (7). USE/ADVANTAGE - Load protection delayed sufficiently to ensure that it is not actuated unnecessarily by voltage variations of very short duration. Switches off one electrical appliance, e.g. storge heater, when other appliance, e.g. throughflow heater, is switched on.