Bivalent point and hybrid switchover

A bivalent point or hybrid switchover is the control condition in a hybrid heat-pump system that decides when a boiler or other supplementary heat source should help or take over from the heat pump. In home-heating paperwork, it may be shown as an outdoor-temperature threshold, a changeover point, a control philosophy or a hybrid-controller setting based on heat demand, flow temperature, tariffs or fuel costs. The term is separate from the hybrid heat pump itself, the boiler, heat-loss calculations, emitter sizing, defrost operation, thermostat settings, Boiler Upgrade Scheme eligibility, MCS certification, DNO approval and any promise of lower bills, lower carbon emissions or uninterrupted comfort.