EPA TYPE III Certification Study Guide - HET-190 - Basic Systems - Purge Unit - Leak Detection and Repair - Recovery Basics

Oct 4, 2026

Uploaded by nayy☆

EPA TYPE III Certification Study Guide HET-190 covers low-pressure refrigeration systems used in chillers and related equipment. It explains how to charge an evacuated system with vapor only at first to prevent freezing, how rupture discs protect low-side pressure, and where key components such as the evaporator charging valve and discharge paths are located. It also addresses oil-acid testing after failures, purge-unit operation to remove non-condensables, hydrostatic and vacuum leak testing methods with safeguards, and fundamentals of refrigerant recovery and push-pull procedures, including pressure limits to protect safety devices.

LanguageEnglish

CategoryExam

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

Basic Systems

Purge Unit

Leak Detection and Repair

Recovery Basics - Type III

Recovery Procedures - Type III

EPA TYPE III Certification Study Guide HET-‐190 Basic Systems 1. Type III certification is for equipment that uses low-‐pressure refrigerant (e.g. R-‐123, R-‐11) . 2. Low-‐pressure units are mostly chillers. A chiller is a refrigeration unit that cools water or other liquid (not air) . The chilled liquid is used to cool large buildings or for industrial processes. 3. Chillers are usually charged with liquid refrigerant through a charging valve in the evaporator. 4. Initially (first), charge the evacuated system with vapor only. This is to prevent the water in the system from freezing. a. Watch the gauge pressure. b. Convert gauge pressure to temperature using a P-‐T chart. c. When the pressure corresponds to a temperature above about 36°F (just above the freezing point of water), liquid refrigerant can be charged. 5. Chillers have a rupture disc as a safety device to relieve excessive pressure on the low side of the system. [To rupture means to tear or break open with force.] 6. The rupture disc is usually set to open at 15 psig. 7. The rupture disc is installed on the low side of the system, in the suction line, between the evaporator and the inlet to the compressor. 8. The rupture disc discharges (vents) to the outdoors. 9. The chilled water pump should be running during refrigerant recovery. This prevents the water from freezing as refrigerant pressure is reduced. 10. A chiller evaporator consists of refrigerant lines enclosed in a shell. Water circulates in the shell, around the refrigerant lines. Cutaway view of a chiller shell, exposing refrigerant lines to view. Whitman, W. C. et al. (2009) . Refrigeration and Air Conditioning Technology. 6th Ed. Fig. 48-‐41, pg. 1270. HET-‐190 – ESL Support TYPE III Study Guide page 2 11. The lowest access point on a low-‐pressure unit is the evaporator charging valve. 12. If a unit has had a leak or major component failure, an oil sample should betaken and tested for acids. 13. If a system is not fully evacuated, compressor head pressure can rise. 14. If a low-‐pressure system is idle (not operating), system pressure should be maintained slightly above atmospheric pressure to prevent air from entering the system. Purge Unit 15. Type III systems operate at pressures below atmospheric pressure. Leaks cause air and moisture to enter (not escape from) the system and cause problems. 16. Most leaks are around gaskets and fittings. The shaft seal on open (not hermetically sealed) compressors is a common location of leaks. 17. When air leaks into a chiller it accumulates at the top (highest point) of the condenser. It stays there because air is non-‐condensable. 18. Air and water vapor are removed by a purge unit (or system) . [To purge means to remove or to get rid of. A purge unit purges a system of non-‐condensables.] 19. The purge unit consists of a purge compressor, an oil separator and a purge drum. [A drum is a large storage container.] 20. The purge compressor pulls non-‐condensables and some refrigerant vapor from the evaporator and sends it to the oil separator. The oil is returned to the purge compressor. 21. In the purge drum, any refrigerant is separated from non-‐condensables. The refrigerant is returned to the system. The non-‐condensables are vented to the atmosphere. 22. High efficiency purge units minimize the loss of refrigerant to the atmosphere. Leak Detection and Repair 23. Common signs of leaking: (i) The purge system runs excessively; (ii) excessive moisture in the purge unit; (iii) high head pressure. 24. A hydrostatic test is used to check tubing for leaks. 25. Drain water circuits before testing. This ensures that moisture will not be drawn into the refrigerant circuit. HET-‐190 – ESL Support TYPE III Study Guide page 3 26. Test Type III equipment for leaks by increasing pressure in the system. Hot water (at a controlled temperature) in the chiller tubes, heating blankets or nitr

FAQs

What type of equipment qualifies for EPA TYPE III certification?

Type III certification applies to equipment that uses low-pressure refrigerant such as R-123 or R-11.

Why is vapor charged first when charging an evacuated system?

Charging the evacuated system with vapor only prevents the water in the system from freezing.

How do purge units help in Type III systems?

Purge units remove non-condensable gases and some refrigerant vapor; the separated refrigerant returns to the system while non-condensables are vented to the atmosphere.

Oct 4, 2026

Uploaded by nayy☆