单选题Before starting an air compressor, It should be （）.AturnedBoil level checkedCfilled with waterDA and B
单选题
Before starting an air compressor, It should be （）.
A
turned
B
oil level checked
C
filled with water
D
A and B
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If the head pressure of a reciprocating refrigeration compressor is excessiveA.the relief valve should open before the high pressure cutoutB.the relief valve should open and allow the excess refrigerant to flow to the receiverC.the high pressure cutout switch should operate before the relief valve opensD.you should close the discharging valve
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