3. Open the shutoff valves of the water-cooled condenser.

4. Make certain the liquid line solenoid valve(s) is on automatic control.

5. Open the liquid line shutoff valve.

6. Back-seat the compressor suction and discharge valves.

7. Close the system master electrical disconnect switch.

8. Start the system.

9. After the system has operated for 15 to 20 minutes, check the compressor oil level sight glass, oil pressure, and the liquid line sight glass. If satisfactory, readjust the system temperature controller to the proper temperature setting.

SAFETY WARNINGS

Most units used for comfort air conditioning operate using R-12 or R-22 refrigerants that are not toxic except when decomposed by a flame. If the liquefied refrigerant contacts the eyes, the person suffering the injury must be taken to a doctor at once.

Should the skin come in contact with the liquefied refrigerant, the skin is to be treated as though it had been frostbitten or frozen. Refer to NAVEDTRA 13119,

Standard First Aid for Treatment of Frostbite.

Do not adjust, clean, lubricate, or service any parts of equipment that are in motion. Ensure that moving parts, such as pulleys, belts, or flywheels, are fully enclosed with proper guards attached.

Before making repairs, open all electric switches controlling the equipment. Tag and lock the switches to prevent short circuits or accidental starting of equipment. When moisture and brine are on the floor, fatal grounding through the body is possible when exposed electrical connections can be reached or touched by personnel. De-energize electrical lines before repairing them, and ground all electrical tools.

Q9. What are the two types of self-contained air-conditioning units?

Q10. Who normally operates a window air-conditioning unit?

Q11. Floor units are often referred to as what type of unit?

Q12. What type of unit cools and heats by reversing its cycle?

Q13. The reversing valve changes the direction of hot gas from what component to what other component in the system?

Q14. Heat pumps operating below 45F develop what problem on the outside coils?

Q15. When the capacity of a heat pump matches the heat loss, it has reached what point?

Q16. What are the two most common evaporators used for water chiller systems?

Q17. Dry-expansion evaporators are controlled by what type of expansion valve?

Q18. Why is a tube-within-a-tube condenser popular?

Q19. Condensers can be cleaned in what two ways?

Q20. Refrigerant coils should be cleaned at least how often?

MAJOR SYSTEM COMPONENTS AND CONTROLS

Learning Objectives: Recognize and understand different types of cooling towers, compressors, and controls. Understand basic maintenance requirements for cooling towers. In this section, cooling towers and compressors which are the two major components of an air-conditioning system are discussed. In addition, the major control elements of an air-conditioned system are also covered.

COOLING TOWERS

Cooling towers are classified according to the method of moving air through the tower as natural draft, induced draft, or forced draft (figs. 7-19 and 7-20).

Natural Draft

The natural draft cooling tower is designed to cool water by means of air moving through the tower at the low velocities prevalent in open spaces during the summer. Natural draft towers are constructed of cypress or redwood and have numerous wooden decks of splash bars installed at regular intervals from the bottom to the top. Warm water from the condenser is