An integrated air conditioning system , comprising: a first air conditioning unit (10-1) having a first refrigeration circuit comprising a first evaporator with a first input (34-2) and a first output , a first compressor ; a second air conditioning unit (10-2) having a second refrigeration circuit comprising a second evaporator with a second input (34-2) and a second output , and a second compressor ; a first conduit fluidly connecting said first input with said second output; and a second conduit fluidly connecting said second input with said first output; said first and second conduits and said first and second evaporators form a working fluid circuit ; said first and second refrigeration circuits being in heat-exchange communication with said working fluid circuit ; characterised in that : the first refrigeration circuit comprises a first pump ; the second refrigeration circuit comprises a second pump ; the first refrigeration circuit is switchable between a cooling mode in which the first pump is bypassed and the first compressor urges refrigerant through the first refrigeration circuit and a free-cooling mode in which the first compressor is bypassed and the first pump urges refrigerant through the first refrigeration circuit; and in that the second refrigeration circuit is switchable between a cooling mode in which the second pump is bypassed and the second compressor urges the refrigerant through the second refrigeration circuit and a free-cooling mode in which the second compressor is bypassed and the second pump urges refrigerant through the second refrigeration circuit. a first air conditioning unit (10-1) having a first refrigeration circuit comprising a first evaporator with a first input (34-2) and a first output , a first compressor ; a second air conditioning unit (10-2) having a second refrigeration circuit comprising a second evaporator with a second input (34-2) and a second output , and a second compressor ; a first conduit fluidly connecting said first input with said second output; and a second conduit fluidly connecting said second input with said first output; said first and second conduits and said first and second evaporators form a working fluid circuit ; said first and second refrigeration circuits being in heat-exchange communication with said working fluid circuit ; characterised in that : the first refrigeration circuit comprises a first pump ; the second refrigeration circuit comprises a second pump ; the first refrigeration circuit is switchable between a cooling mode in which the first pump is bypassed and the first compressor urges refrigerant through the first refrigeration circuit and a free-cooling mode in which the first compressor is bypassed and the first pump urges refrigerant through the first refrigeration circuit; and in that the second refrigeration circuit is switchable between a cooling mode in which the second pump is bypassed and the second compressor urges the refrigerant through the second refrigeration circuit and a free-cooling mode in which the second compressor is bypassed and the second pump urges refrigerant through the second refrigeration circuit. the first refrigeration circuit comprises a first pump ; the second refrigeration circuit comprises a second pump ; the first refrigeration circuit is switchable between a cooling mode in which the first pump is bypassed and the first compressor urges refrigerant through the first refrigeration circuit and a free-cooling mode in which the first compressor is bypassed and the first pump urges refrigerant through the first refrigeration circuit; and in that the second refrigeration circuit is switchable between a cooling mode in which the second pump is bypassed and the second compressor urges the refrigerant through the second refrigeration circuit and a free-cooling mode in which the second compressor is bypassed and the second pump urges refrigerant through the second refrigeration circuit. <EOS>