Disclosed are cascade refrigerant systems for providing cooling of air located in an enclosure that is occupied by or which will be exposed to humans or other animals during normal use, wherein systems includes; (1) a first, relatively low temperature heat transfer circuit having a first evaporator located within the enclosure and a first heat transfer fluid in the low temperature heat transfer circuit; (2) a second heat transfer circuit located substantially outside the enclosure comprising a second heat transfer fluid; (3) a heat exchanger which serves as the condenser in the low temperature circuit thermally coupled with the high temperature circuit by virtue of rejecting heat into the second heat transfer fluid; and (4) in the high temperature loop of a heat exchanger which transfers heat from the second heat transfer fluid exiting from a high temperature condenser to the portion of the second heat transfer fluid which is traveling to the suction side of the compressor.