Thermostat with load relay cycling feature

Abstract

A thermostat for an environmental control load that includes a temperature sensor, a timer, and a controller, and a method of controlling the thermostat that allows temporary system outages including, but not limited to, outages caused by lockouts or failure of pulsed relays to operate, to be corrected automatically, by the thermostat itself. The environmental control load may include a heating system such as a heat pump or a millivolt heating system, although the thermostat and its method of operation could also be employed with cooling systems, or heating and cooling systems. The controlled load may be one that has a 'lockout' mode to prevent activation when a problem is detected, such as a reduction in gas pressure. The temperature sensor detects whether, for example, a request for heat issued by the controller has been satisfied, or alternately, if the ambient temperature has risen within some period of time, usually about two hours. If the ambient temperature has not satisfied this condition within two hours, the environmental control load is turned off, and then on, to recycle and overcome the lockout condition, if the load is resettable and the condition causing the lockout has passed. This resetting may occur only once, or may be repeated after another period of time, with the repetitions optionally being limited in number. The thermostat can safely be used without noticeable degradation in service even with nonrecyclable systems.