Patent ID: 8385729

Claim:
Liquid heating apparatus comprising: first apparatus operative to transfer refrigerant heat to a liquid; second apparatus operative to transfer electrical heat to the liquid; and a control system having a heating mode operative, in a heating cycle initiated in response to a sensed demand for liquid heating, to: (1) initially utilize said first apparatus, at the start of the heating cycle, to transfer refrigerant heat to the liquid while preventing operation of said second apparatus for a predetermined lockout time period, (2) thereafter utilize said second apparatus to supplement the refrigerant heating of the liquid with electrical heating thereof if the heating demand has not been satisfied by the previous refrigerant heating of the liquid, and then (3) terminate the operation of both the first heating apparatus and the second heating apparatus at the end of the heating cycle when the demand for liquid heating is satisfied, the lockout of the second apparatus during each heating cycle in said heating mode being initiated only at the start of such heating cycle.