Bill Nielsen
Inter-Provincial Teaching
3rd and 4th Class Stationary Engineering

5. COMPRESSORS: 

a. State the main types of refrigeration compressors and give a brief description of each type stated.

b. Explain the application and the types of ‘booster’ compressors.

c. State and provide a brief description of the main types of prime movers used to drive refrigeration compressors

d. State the difference between ‘hermetic’ and ‘open-type’ reciprocating compressors.

e. Describe the methods used to prevent leakage of refrigerant at the compressor shaft, and prevent liquid refrigerant from entering compressor.

f. List and provide a description of the different methods employed to control the ‘capacity’ of refrigeration compressors.

g. Sketch and describe a two-stage centrifugal chiller. 

6. CONTROLS AND ACCESSORIES: 

a. List and describe the six types of refrigerant metering devices used to control the flow of refrigerants.

b. Sketch and fully describe the operation of a thermostatic expansion valve.

c. Define primary control and secondary control.

d. Describe the function, principle of operation, and the location(s) of the following operational controllers:

I. Temperature and/or pressure actuated.

II. Humidity actuated.

III. Evaporator pressure regulator.

IV. Cooling water regulating valve.

e. List the “limiting” and “safety” controls used in a refrigeration system, and describe the operation of each type listed.

f. State the function of, and the location, of the following components in a system:

I. Oil separators and suction strainers.

II. Suction traps, strainer-driers.

III. Moisture indicators, crankcase heaters.

IV. Oil stills, purge and charging valves.

V. Pressure relief devices.

g. Describe the type of piping/tubing allowed for the different types of refrigerants.

h. Describe the use of receivers in a refrigeration system, their location, and the Code required safety fittings attached.

i. Describe the methods employed to control humidity inside skating rinks. 

7. CONDENSERS AND COOLING TOWERS: 

a. List and describe the different types of air-cooled and water-cooled condensers.

b. Sketch and fully describe the evaporative type condenser, explain the effects of humidity on this type of condensers’ operation.

c. List the main factors on which the rate of heat transfer is dependent on in a cooling tower.

d. Explain the need for water treatment and provide a brief description of the water tests required. 

8. EVAPORATORS AND COOLING COILS: 

a. List and describe the different types of evaporators.

b. Describe the differences between a ‘dry expansion’ and a ‘flooded expansion’ evaporator.

c. Explain the operation of chillers and cooling coils. 

9. OPERATION AND MAINTENANCE: 

a. Describe the refrigeration leak test required prior to starting up a newly installed refrigeration system, and describe how refrigerant leaks are detected in a plant that is in operation.

b. Describe how you would startup and shut down a single-stage refrigeration system.

c. Describe how to purge air from an operating system, how refrigerant is added to a system, and how to add oil to a running compressor.

d. State some common reasons for the following:

I. Failure of a compressor to start, compressor short cycling.

II. Continuous running of the compressor when not required, system not cooling as required.

III. Discharge pressure too high, or too low; suction pressure too high, or too low.

e. Describe the maintenance normally performed on compressors, refrigeration plant pumps, valves, metering devices, evaporators, and condensers to ensure safe and continuous operation.

f. Describe the precautions to be taken when draining oil separators to prevent unsafe conditions.

g. List and describe methods used to defrost evaporators.

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