4.0.1 — General Learning Outcomes

Upon successful completion of this section, the apprentice will be able to:

• Identify filter-driers, sight glasses, and moisture indicators; explain their function and location; and diagnose a restricted drier using temperature and pressure checks.
• Describe the function of suction-line/liquid-line heat exchangers and liquid receivers; explain receiver sizing and safe service practices; and recognize post-service valve-position faults.
• Explain how oil separators and suction accumulators protect compressors; diagnose oil separator and accumulator failures; and apply piping best practices that support reliable oil return.
• Describe the operation of pressure controls, EPRs, CPRs, and head pressure regulators; select appropriate pressure relief devices; and respond correctly to a relief event.

4.0.2 — Section 4 — Lessons at a Glance

Section 4 covers the accessory devices that protect refrigeration system components from the most common failure-causing contaminants and conditions.

4.0.3 — Accessory Device Quick Reference

Each major accessory type in Section 4 serves a distinct function within the refrigerant circuit. Use this grid as a quick index before each lesson.