Integrated heat pump system

In a heat pump system containing an indoor fan coil unit and an outdoor fan coil unit that are selectively connected on one side to either the suction line or the discharge line of a compressor by a reversing valve and on the other side by a liquid line containing an expansion valve whereby the flow of refrigerant through the system can be reversed to provide either cooling or heating to an indoor comfort zone, the improvement comprising

• a liquid to refrigerant heat exchanger having a water circuit that is in heat transfer relation with a first refrigerant condensing circuit and a second refrigerant evaporating circuit whereby energy in the condensing circuit is transferred into the water circuit and energy in the water circuit is transferred into the evaporating circuit,
• said condensing circuit being connected at one side to the discharge line of the compressor and at the other side to the reversing valve whereby a portion of the energy in the refrigerant leaving the compressor is available to heat water passing through the water circuit,
• said water circuit being connected into a hot water system,
• said evaporating circuit being connected into an evaporator line that is joined at one end to the liquid line between the indoor fan coil unit and the expansion valve and at the other end to the suction line of the compressor,
• a first control valve positioned in the liquid line between the evaporator line and the indoor fan coil unit,
• a second control valve in the evaporator line positioned between the liquid line and the evaporating circuit, and
• control means for normally holding the first valve in an open condition and the second valve in a closed condition when heating or cooling is being provided to the comfort zone and for periodically closing said first valve and opening said second valve to defrost the outdoor coil whereby energy in the hot water system is used to evaporate refrigerant as it is being returned to the compressor through the refrigerant evaporating circuit.