NOVELTY - The installation has a refrigerating unit comprising a compressor (7) that is driven by a heat engine (8) and an evaporator (13). A thermochemical cooling system (15) includes a vessel (23) containing a liquefied gas that is capable of combining with a reactive product contained in a reactor (17). The cooling system includes an evaporator (25) and a condenser (21). The evaporator of the cooling system is in thermal contact with a refrigerant circuit of the refrigerating unit upstream from the evaporator of the refrigerating unit.    USE - Installation for refrigeration and maintenance of temperature of an isothermal enclosure that is placed on a vehicle such as semi-trailer, for transport of goods in a cold state. Can also be used in a lorry.    ADVANTAGE - The evaporator of the cooling system is in thermal contact with the refrigerant circuit of the refrigerating unit upstream from the evaporator of the refrigerating unit, thus allowing to reduce power of the refrigerating unit, and hence reducing dimensioning of the refrigerating unit and reducing cost of the refrigerating unit. The installation decreases the power of the compressor and the motor that drives the compressor. The installation decreases pollution emitted by diesel engine of the vehicle, and reduces operating time at the time of temperature setting phase. The installation has a simple structure and provides savings on energy spent for regeneration of thermochemical system.    DETAILED DESCRIPTION - The product is a mixture of a reactive salt and natural expanded graphite. An INDEPENDENT CLAIM is also included for a method for refrigeration and maintenance of temperature of an isothermal enclosure.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an installation for refrigeration and maintenance of temperature of an isothermal enclosure.    Compressor (7)    Heat engine (8)    Evaporator of refrigerating unit (13)    Thermochemical cooling system (15)    Reactor (17)    Condenser (21)    Vessel (23)    Evaporator of cooling system (25)