单选题If a refrigeration system compressor crankcase is sweating, you should （）.A add refrigerant to the systemB adjust the thermal expansion valve to the proper settingC adjust the float valve to the proper holding pressureD open the hand expansion valve

Low compressor head pressure in a refrigeration system can be caused by ___.

A.insufficient condenser cooling water

B.excessive condenser cooling water

C.air in the refrigeration system

D.excessive refrigerant in the system

The sensing line for the low pressure cutout switch to a refrigeration system is located ______.

A.in the chill box(冰箱)

B.before the receiver

C.on the suction side of the compressor

D.on the discharge side of the compressor

If the refrigeration compressor crankcase is sweating, the cause may be due to

A.a shortage of refrigerant

B.the compressor running continuously

C.liquid refrigerant returning to the compressor

D.the compressor short cycling on the high pressure cutout

Sweating of the refrigeration system compressor crankcase is caused by_______ .

A.too much superheat

B.insufficient superheat

C.suction pressure too low

D.excessive refrigerant returning to the compressor

Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur when the compressor

A.has run continuously for a long period

B.suction pressure is below normal

C.oil level is below normal

D.starts after a long idle period