單項選擇題The refrigeration system low pressure cutout switch is actuated by （）.

A.an electric system manager
B.a sensing bulb at the tail coil of the evaporator
C.pressure changes in the suction line
D.failure of the king solenoid valve


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1.單項選擇題Hydraulic machinery failures are commonly caused by contamination of the hydraulic fluid and （）.

A.fluid friction
B.fluid turbulence
C.component misalignment
D.pressure surges

2.單項選擇題When you adjust a thermostatic expansion valve, （）.

A.refrigerant must be bled off the sensing line before adjustments are made
B.all refrigerant must be pumped into the receiver before adjustments are made
C.time must be allowed for conditions to stabilize in the evaporator before further adjustments are made
D.all refrigerant must be routed through the dehydrator while changing the superheat setting

3.單項選擇題If a centrifugal pump were continually operated with the discharge valve closed, the （）.

A.motor controller overload would open
B.pump would eventually overheat
C.relief valve would continuously cycle open
D.motor would overheat

4.單項選擇題A double suction centrifugal pump impeller has been installed in the reverse direction, and will （）.

A.have a greater head capacity
B.operate with increased impeller efficiency
C.discharge through the suction side of the pump casing
D.require more power to run the shaft

5.單項選擇題Hydraulic machinery failures are commonly caused by misalignment of the system components and by （）.

A.hydraulic fluid contamination
B.excessive fluid friction
C.turbulent fluid flow
D.fluid pressure surges