153 Copyright by Goodheart-Willcox Co., Inc. Aft er studying this chapter, you will be able to: • Explain the importance of refrigerant fl ow and pressure control in the evaporator. • Explain the construction and purpose of thermostatic expansion valves. • Explain the construction and purpose of evaporator pressure control devices. • Identify the major types of evaporator pressure control devices. • Explain the construction and purpose of compressor clutch control devices. • Identify the major types of compressor clutch control devices. • Explain the construction and purpose of high and low pressure cutoff switches. • Explain the purpose of pressure relief valves. ambient air switch ambient temperature switch capillary tube clutch cycling control piston cutout switch duty cycle duty solenoid electronic expansion valve electronic orifi ce tube equalizer evacuated bellows fl exible diaphragm H-block high pressure cutoff switch high temperature cutout switch hot gas valve low pressure cutoff switch pilot operated absolute (POA) valve pressure cutoff switch pressure cycling switch pressure transducers sensing bulb superheat spring temperature cutoff switch temperature cutout thermistor thermostatic temperature cycling switch trinary cutoff switch Technical Terms Chapter 10 Control Valves and Switches