Refrigeration system with free-cooling

1. A system for cooling air for use with a liquid cooling fluid loop, the system comprising:

a first refrigerant circuit with an air-cooled first condenser, all heat generated by the first refrigerant circuit is rejected through the air-cooled first condenser;

a free-cooling loop with a free-cooling loop coil located upstream of the air-cooled first condenser of the first refrigerant circuit;

a second refrigerant circuit with a liquid-cooled second condenser, all heat generated by the second refrigerant circuit is rejected through the free-cooling loop coil of the free-cooling loop;

a control device for controlling the operation of the system between a first mode, a second mode, and a third mode;

wherein when operating in the first mode, only the free-cooling loop exchanges heat directly with liquid cooling fluid in the liquid cooling fluid loop to cool the liquid cooling fluid, when operating in the second mode, the first refrigerant circuit is engaged and the second refrigerant circuit is not engaged, and when operating in the third mode, the free-cooling loop interacts with the second refrigerant circuit to reject heat of the second refrigerant circuit through the free-cooling loop.

2. The system as recited in claim 1 , wherein the free-cooling loop includes a valve that directs free-cooling liquid to the second condenser of the second refrigerant circuit when the system is operating in the third mode.

3. The system as recited in claim 2 , wherein the valve of the free-cooling loop directs the free-cooling liquid to a heat exchanger which is positioned in-line with the liquid cooling fluid loop when the system is operating in the first mode.

4. The system as recited in claim 2 , wherein the first refrigerant circuit includes a first compressor, the first condenser, a first expansion device, and a cooler, the cooler cooperates with the liquid cooling fluid in the liquid cooling fluid loop to cool the liquid cooling fluid.

5. The system as recited in claim 4 , wherein the cooler includes two evaporators, a first evaporator positioned in the first refrigerant circuit and a second evaporator positioned in the second refrigerant circuit.

6. The system as recited in claim 5 , wherein the second refrigerant circuit includes a second compressor, the second condenser, and the cooler, the second compressor supplies pressurized refrigerant vapor to the liquid-cooled condenser, the liquid-cooled condenser cools and condenses the refrigerant.

7. The system as recited in claim 6 , wherein a second expansion device coverts high pressure liquid refrigerant to low pressure fluid, the cooler cools the liquid cooling fluid in the liquid cooling fluid loop as the low pressure fluid evaporates, absorbing heat from the liquid cooling fluid in the liquid cooling fluid loop.

8. The system as recited in claim 1 , wherein the free-cooling loop includes a glycol coil, a glycol pump, and a three-way valve that connects an outlet of the glycol pump to either a glycol-water heat exchanger or the second condenser of the second refrigerant circuit.

9. The system as recited in claim 8 , wherein a fan moves air through the glycol coil and the air-cooled first condenser of the first refrigerant circuit.

10. The system as recited in claim 1 , wherein free-cooling liquid provided in the free-cooling loop has a lower freezing point temperature than the liquid cooling fluid circulating provided in the liquid cooling fluid loop.

11. The system as recited in claim 1 , wherein free-cooling liquid provided in the free-cooling loop is a freeze-protected fluid to inhibit freezing during periods of low ambient temperatures.