A programmable electronic thermostat is provided for controlling operation of a multistage heating apparatus comprising a heat pump and auxiliary heat. A salient feature is a program which provides for economical recovery from a setback temperature. The program includes logic which determines, at the...http://www.google.de/patents/US4828016?utm_source=gb-gplus-sharePatent US4828016 - Programmable electronic thermostat with means for enabling economical recovery
