EPA 608 Type III — low-pressure: free practice test

25 questions · Type III — low-pressure. Pick an answer for each, then check. Explanations cite the rule each question tests.

1. 1. A low-pressure appliance uses a refrigerant with a boiling point above:

   −50°C0°C10°C at atmospheric pressure50°C

2. 2. Required evacuation level for a low-pressure appliance using recovery equipment made after 11/15/1993:

   0 psig10 in Hg25 mm Hg absolute (≈ 29 in Hg vacuum)4 in Hg

3. 3. Because low-pressure chillers run in a vacuum, the most common contaminant that enters through leaks is:

   OilAir and moisture (non-condensables)Refrigerant of another typeNitrogen

4. 4. A purge unit on a low-pressure chiller functions to:

   Add refrigerant automaticallyRemove non-condensables and moisture from the condenser, venting a small de minimis amount of refrigerantRecover the full charge for serviceRaise system pressure for leak testing

5. 5. When pressurizing a low-pressure chiller for leak testing, the pressure must never exceed:

   10 psig, to protect the rupture disk (typically rated 15 psig)50 psig150 psigAny pressure is fine with nitrogen

6. 6. Refrigerant recovery from a low-pressure chiller should start with:

   Vapor recoveryLiquid recovery first — it is faster — then vapor with the recovery unit and chiller pumps runningOpening the drain valve to atmosphereHeating the oil sump only

7. 7. Water in the tubes of an evacuated low-pressure chiller can:

   Improve recoveryFreeze and rupture the tubes — keep water flowing or drain the tubes during evacuationBe ignoredRaise the rupture-disk rating

8. 8. After recovery, the chiller should be charged by introducing refrigerant as:

   Vapor first, to avoid freezing the water in the tubes, then liquidLiquid first at full speedNitrogen firstThrough the purge unit

9. 9. Which refrigerant is commonly found in older low-pressure centrifugal chillers?

   R-410AR-11 (CFC) and its HCFC replacement R-123R-32R-22

10. 10. A pressure of 25 mm Hg absolute is approximately:

    0 in Hg vacuum15 in Hg vacuum29 in Hg vacuum (near-full vacuum)40 in Hg vacuum

11. 11. R-11 boils at approximately what temperature at atmospheric pressure?

    −41°F0°F75°F (about 24°C)212°F

12. 12. R-123, the HCFC service replacement for R-11, has a low ASHRAE safety-group toxicity rating of B1. Machine rooms using it therefore require:

    Nothing specialA refrigerant vapor monitor/sensor and alarms, with self-contained breathing apparatus available per the mechanical code and ASHRAE 15Only a fire extinguisherOpen windows

13. 13. The rupture disk on a low-pressure chiller relieves at approximately:

    15 psig150 psig300 psig1 psig

14. 14. The rupture disk's relief piping should discharge:

    Into the machine roomOutdoors, away from occupied areas, per the mechanical codeInto the cooling towerInto the purge unit

15. 15. An excessive purge-unit run time (frequent purging) on a low-pressure chiller is the classic sign of:

    OverchargeAir leaking INTO the machine through low-side leaksA failed rupture diskToo much oil

16. 16. Before cutting into a low-pressure system for a major repair, the required evacuation is 25 mm Hg absolute. For opening for a MINOR repair where the system will not hold that vacuum, the technician may:

    Skip recoveryBring the system to atmospheric pressure using controlled means (e.g., nitrogen after recovery to 0 psig equivalent) per the rules for leaky appliancesPressurize to 50 psigOpen under deep vacuum

17. 17. Oil removed from a low-pressure chiller during service:

    Contains dissolved refrigerant, which must be recovered (e.g., by heating the oil to 130°F+ during recovery) before disposalIs refrigerant-freeCan be poured down the drainMust be returned to the machine

18. 18. During charging of an evacuated low-pressure chiller, liquid refrigerant added too early can:

    Speed the process safelyFlash and drop temperatures below freezing, cracking evaporator tubes filled with waterOverheat the compressorDamage the purge unit only

19. 19. Leak-testing a low-pressure chiller by pressurizing with heated refrigerant vapor or controlled warm water is preferred over nitrogen above 10 psig because:

    Nitrogen is illegalAny test pressure above ~10 psig risks the rupture disk (≈15 psig) and vessel ratingRefrigerant is cheaperWater finds leaks faster

20. 20. The recovery unit used on low-pressure systems differs from high-pressure recovery units in that it must:

    Have no compressorHandle deep vacuums and large vapor volumes (low-pressure refrigerants have high specific volume) — purpose-built machines are usedBe smallerRun on gasoline

21. 21. During liquid recovery from a chiller, running the chiller's water pumps is required to:

    Cool the compressorPrevent tube freeze-up as the evaporating refrigerant chills the vesselSpeed the purge unitCirculate oil

22. 22. After recovery, a low-pressure system that will stand open for repairs should be:

    Left under vacuumBroken to atmospheric with dry nitrogen and kept slightly positive/dry to limit moisture entryFilled with waterHeated to 200°F

23. 23. A 'prevailing vacuum' recovery ending pressure of 25 mm Hg absolute applies to equipment manufactured:

    Before Nov 15, 1993 (25 in Hg for older equipment... )On or after Nov 15, 1993 — older recovery equipment must reach 25 in Hg vacuumAny date — always 4 in HgOnly after 2020

24. 24. Which instrument proves a low-pressure chiller is holding its required deep vacuum after recovery?

    A compound gauge onlyAn electronic micron/absolute-pressure gauge read over time with the recovery unit valved offA P/T chartA sight glass

25. 25. If the standing vacuum on a recovered low-pressure chiller steadily rises toward atmospheric overnight, the cause is:

    Normal behaviorA leak admitting air, or refrigerant still outgassing from oil — locate and repair before opening or chargingThe micron gauge is brokenThe rupture disk operated