Heat pump with freeze-up prevention

Apparatus for conditioning a fluid temperature-wise comprising:

• a. a fluid handler and fluid path means for circulating said fluid in a path in heat exchange relationship with a refrigerant fluid;
• b. at least two refrigerant heat exchangers;
• a first of the heat exchangers being disposed in the path of the fluid such that the fluid is passed in heat exchange relationship therewith, and a second of the refrigerant heat exchangers being at least disposable in a heat exchange fluid circuit for circulating the refrigerant in heat exchange relationship with a heat exchange fluid and at least disposable in a path of ambient air for circulating said refrigerant in heat exchanger relationship with the ambient air;
• c. at least one compressor connected into a refrigerant circuit for efficiently compressing the refrigerant from its inlet pressure to its discharge pressure under conditions of operation of the refrigerant circuit;
• d. at least one throttling valve connected at the inlet of a heat exchanger in which liquid refrigerant is being vaporized,
• e. a refrigerant circuit serially connecting said heat exchangers, throttling valve and compressor and defining a flow path for said refrigerant;
• f. means for selecting the heat exchangers and direction of flow of refrigerant therethrough for selecting a particular mode of operation of the heat pump;
• g. refrigerant disposed in said refrigerant circuit and adapted to be circulated in a selected flow path for transferring heat at a coeffecient of performance greater than one;
• h. a source of heat exchange fluid;
• i. heat exchange fluid circulating means for circulating said heat exchange fluid in a heat exchange circuit and in heat exchange relationship with said refrigerant;
• and
• j. a heat exchange circuit serially connecting said heat exchange fluid source, circulating means and second refrigerant-heat exchange fluid heat exchanger;
• and
• k. control means having means to sense ambient dew point temperature and refrigerant temperature in said second heat exchanger for effecting circulation of said heat exchanger fluid through said second heat exchanger to keep the temperature of evaporating refrigerant above the lowest of dew point temperature of ambient air and 32.degree. F.;
• whereby said heat exchange fluid can be circulated through said second heat exchanger to keep said second heat exchanger operating efficiently as an evaporator.