A refrigeration system comprising: a first refrigeration loop comprising: at least one first compressor fluidly connected to a first suction line and a first discharge line; at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line; a condenser operable to receive refrigerant from the at least one second compressor; a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line; a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; the refrigeration system being characterised by a heat exchanger operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; and a valve disposed between the first evaporator and the first suction line, wherein: the first suction line receives refrigerant from the first evaporator when the valve is in a first position; the second suction line receives refrigerant from the first evaporator when the valve is in a second position; and the at least one first compressor is bypassed when the valve is in the second position; and a second refrigeration loop comprising: at least one third compressor; the heat exchanger operable to receive refrigerant from the third compressor; and a third evaporator operable to receive refrigerant from the heat exchanger and discharge refrigerant to the at least one third compressor. a first refrigeration loop comprising: at least one first compressor fluidly connected to a first suction line and a first discharge line; at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line; a condenser operable to receive refrigerant from the at least one second compressor; a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line; a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; the refrigeration system being characterised by a heat exchanger operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; and a valve disposed between the first evaporator and the first suction line, wherein: the first suction line receives refrigerant from the first evaporator when the valve is in a first position; the second suction line receives refrigerant from the first evaporator when the valve is in a second position; and the at least one first compressor is bypassed when the valve is in the second position; and at least one first compressor fluidly connected to a first suction line and a first discharge line; at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line; a condenser operable to receive refrigerant from the at least one second compressor; a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line; a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; the refrigeration system being characterised by a heat exchanger operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; and a valve disposed between the first evaporator and the first suction line, wherein: the first suction line receives refrigerant from the first evaporator when the valve is in a first position; the second suction line receives refrigerant from the first evaporator when the valve is in a second position; and the at least one first compressor is bypassed when the valve is in the second position; and the first suction line receives refrigerant from the first evaporator when the valve is in a first position; the second suction line receives refrigerant from the first evaporator when the valve is in a second position; and the at least one first compressor is bypassed when the valve is in the second position; and a second refrigeration loop comprising: at least one third compressor; the heat exchanger operable to receive refrigerant from the third compressor; and a third evaporator operable to receive refrigerant from the heat exchanger and discharge refrigerant to the at least one third compressor. at least one third compressor; the heat exchanger operable to receive refrigerant from the third compressor; and a third evaporator operable to receive refrigerant from the heat exchanger and discharge refrigerant to the at least one third compressor.