................ are snap-acting valves that open and close very fast when the electrical energy is applied to the coil.

• Contactors

• Condensers

• Relays

• Solenoid valves

Random defrost is accomplished .................

• with a timer

• using a high pressure control

• using a low pressure control

• when the system has enough reserve capacity to cool more than the load requirement

Defrost using internal heat is accomplished using ..............

• a sail switch

• electric heating elements

• hot gas from the compressor

• mullion heaters

When a system pumps down, where is the refrigerant stored?

• Condenser and receiver.

• Evaporator and compressor

• Condenser and compressor.

• Both a and c.

The normal position for a suction service valve during normal operation is ..........

• back-seated

• front-seated

• mid-seated

• Any of the three.

Two-temperature operation of a refrigeration system is necessary when .......

• the compressor must be protected from overloading

• more than one evaporator is used with a compressor

• the coil in the evaporator is excessively long

• a multi-circuit distributor is used

Frequently on smaller condensing units, one fan will run continuously and the other fan will be cycled on and off with a(n) .............

• ambient temperature controller

• ambient pressure valve

• thermal expansion valve

• thermal control valve

How does the receiver ensure that only 100% liquid refrigerant enters the liquid line?

• By means of a dip tube.

• It only allows refrigerant to enter the liquid line when it is filled with liquid.

• The spring-loaded relief valve opens

• None of the above are correct.

Which of the following is another type of low-ambient temperature head pressure control?

• Air volume control using shutters and fan cycling.

• Programmed defrost timer.

• Timer and liquid line solenoid for automatic pump down.

• Compressor internal heat.

The refrigeration compressor motor can be operated at about .................. % over its rated capacity without harm during the pulldown.

• 5

• 10

• 15

• 20