Air conditioner

1. An air conditioner having a plurality of outdoor units and a plurality of indoor units connected via a common piping to transfer refrigerant therebetween, the air conditioner comprising:

a first outdoor unit to provide heat;

a second outdoor unit to defrost a heat exchanger of the second outdoor unit; and

a first refrigerant guide unit in the second outdoor unit to guide a flowing direction of the refrigerant;

wherein

the refrigerant discharged from the first outdoor unit is circulated through the heat exchanger of the second outdoor unit,

the second outdoor unit comprises:

a compressor to compress liquid refrigerant, and

a second bypass line; and

a third valve;

wherein a part of liquid refrigerant, which is transferred to the common piping from the heat exchanger, is directed to a suction inlet of the compressor through the third valve and the second bypass line.

2. The air conditioner as set forth in claim 1 , wherein the first refrigerant guide unit comprises:

a first bypass line; and

at least one valve to direct the refrigerant to an inlet of the heat exchanger.

3. The air conditioner as set forth in claim 2 , wherein the at least one valve is a three-way valve.

4. The air conditioner as set forth in claim 3 , wherein the three-way valve is provided on the first bypass line.

5. The air conditioner as set forth in claim 2 , wherein the at least one valve includes first and second valves.

6. The air conditioner as set forth in claim 5 , wherein at least one of the first and second valves is provided on the first bypass line.

7. The air conditioner as set forth in claim 1 , wherein the compressor is a scroll compressor.

8. An air conditioner having a plurality of outdoor units and a plurality of indoor units connected via a common piping to transfer refrigerant therebetween, the air conditioner comprising:

a first outdoor unit to provide heat;

a second outdoor unit to defrost a heat exchanger of the second outdoor unit; and

a first refrigerant guide unit in the second outdoor unit to guide a flowing direction of the refrigerant;

wherein

the refrigerant discharged from the first outdoor unit is circulated through the heat exchanger of the second outdoor unit,

the second outdoor unit further comprises a compressor to compress liquid refrigerant, and

a compression ratio of the compressor is set to be lower than a compression ratio of the compressor during a heating operation.

9. The air conditioner as set forth in claim 1 , wherein the second outdoor unit further comprises an expansion valve coupled to an outlet of the heat exchanger.

10. The air conditioner as set forth in claim 9 , wherein the outdoor expansion valve is opened to an opening level of approximately 100% in response to the defrosting of the heat exchanger.

11. An air conditioner comprising:

a first outdoor unit to provide heat;

a first compressor in the first outdoor unit;

a second outdoor unit to defrost a heat exchanger of the second outdoor unit;

a second compressor in the second outdoor unit;

a common piping connecting the first outdoor unit and the second outdoor unit;

a first refrigerant guide unit in the second outdoor unit to guide a flowing direction of refrigerant, wherein the refrigerant compressed by the first compressor is circulated through the heat exchanger; and

a second refrigerant guide unit in the second outdoor unit to guide a flowing direction of the refrigerant, wherein a part of the refrigerant circulated through the heat exchanger is circulated in the second outdoor unit,

wherein the second refrigerant guide unit comprises:

a second bypass line; and

a valve;

wherein the part of the refrigerant circulated in the second outdoor unit is liquid refrigerant, which is transferred to the common piping from the heat exchanger, and wherein the part of the refrigerant is directed to a suction inlet of the second compressor.

12. The air conditioner as set forth in claim 11 , wherein the first refrigerant guide unit comprises:

a first bypass line diverging from the common piping and connected to an inlet of the heat exchanger; and

a three-way valve provided on the first bypass line.

13. The air conditioner as set forth in claim 11 , wherein the second compressor is a scroll compressor to compress liquid refrigerant.

14. The air conditioner as set forth in claim 11 , wherein the second outdoor unit further comprises an expansion valve coupled to an outlet of the heat exchanger, the expansion valve being opened to an opening level of approximately 100% in response to defrosting the heat exchanger.