EPA 608 Type III Practice Test 3 — Questions and Answers
Question 1: Which refrigerant is the primary replacement for R-11 in new low-pressure centrifugal chillers?
- R-22
- R-134a
- R-123 (Correct answer)
- R-410A
Correct answer: R-123
R-123 (HCFC-123) is the primary retrofit and replacement refrigerant for R-11 in centrifugal chillers. It has a much lower ODP (0.02) than R-11 (ODP 1.0) while operating at similar pressures, allowing existing chiller equipment to be converted. R-134a is used in some medium-pressure centrifugal chillers but operates at higher pressures than R-11 and R-123 systems.
Question 2: What specialized safety equipment is required when working on R-11 or R-123 centrifugal chiller systems?
- Full hazmat suit and Level A protection
- Supplied air respirator or SCBA when entering confined spaces where concentrations may exceed exposure limits (Correct answer)
- High-voltage rubber gloves due to electrostatic charge in low-pressure refrigerants
- Chemical splash goggles and an activated carbon respirator only
Correct answer: Supplied air respirator or SCBA when entering confined spaces where concentrations may exceed exposure limits
R-11 and R-123 have higher toxicity ratings (ASHRAE Class B). When working in enclosed machine rooms or confined spaces where refrigerant concentrations could reach dangerous levels, technicians must use supplied-air respirators or self-contained breathing apparatus (SCBA). Half-face air-purifying respirators are not adequate for high-concentration emergency situations in confined chiller rooms.
Question 3: A centrifugal chiller's purge unit log shows an increase in air removal over the past month. What does this indicate?
- Normal variation based on load changes in the building
- Increasing system leak rate allowing more air infiltration (Correct answer)
- The refrigerant charge is decreasing and should be topped off
- The purge unit is malfunctioning and recovering too much gas
Correct answer: Increasing system leak rate allowing more air infiltration
Increasing purge unit operation on a centrifugal chiller is a key indicator of an increasing leak rate. As leaks allow more air to enter the vacuum-side system, the purge unit must run more frequently to remove the accumulated non-condensables. Technicians and building operators should monitor purge unit logs as an early leak detection tool — rising purge rates require immediate leak investigation.
Question 4: What unique challenge does a power outage present to a centrifugal chiller system operating at low pressure?
- The compressor may restart in reverse rotation, causing damage
- Air can infiltrate through mechanical seals when the compressor stops and system pressure equilibrates below atmospheric (Correct answer)
- High pressure will build in the condenser when cooling water flow stops
- The refrigerant will solidify in the evaporator without constant circulation
Correct answer: Air can infiltrate through mechanical seals when the compressor stops and system pressure equilibrates below atmospheric
When a centrifugal chiller loses power, the compressor stops and system pressure equilibrates. If the system pressure rises above local atmospheric pressure during warmup (some refrigerants), refrigerant may vent. More critically, as the system cools, pressure may drop below atmospheric again, potentially drawing air through shaft seals. Proper startup procedures after power outages include checking for air infiltration.
Question 5: What distinguishes a centrifugal compressor from a reciprocating compressor used in large chiller systems?
- Centrifugal compressors use pistons; reciprocating compressors use impellers
- Centrifugal compressors raise refrigerant pressure using rotating impellers (kinetic energy); reciprocating compressors use pistons (positive displacement) (Correct answer)
- Centrifugal compressors can only be used with low-pressure refrigerants; reciprocating compressors work with high-pressure refrigerants only
- Centrifugal compressors are oil-free while reciprocating compressors require no lubrication
Correct answer: Centrifugal compressors raise refrigerant pressure using rotating impellers (kinetic energy); reciprocating compressors use pistons (positive displacement)
Centrifugal compressors use high-speed rotating impellers to accelerate refrigerant gas, converting kinetic energy to pressure (dynamic compression). Reciprocating compressors use pistons moving in cylinders to compress gas by positive displacement. Centrifugal compressors are better suited to large tonnage low-pressure applications, while reciprocating designs are used across smaller to medium capacity high-pressure systems.
Question 6: Under EPA regulations, when may a low-pressure chiller system owner defer required leak repairs?
- Never — all leaks must be repaired within 30 days of discovery
- When the system is due for retirement within 1 year and continued operation is economically justified
- When annual leak rate is below the 30% threshold after accounting for recovered refrigerant (Correct answer)
- Repair may be deferred indefinitely if refrigerant is fully recovered between each service visit
Correct answer: When annual leak rate is below the 30% threshold after accounting for recovered refrigerant
EPA Section 608 requires owners of appliances with over 50 lbs of charge to repair leaks when the annual leak rate exceeds the applicable threshold (10% for comfort cooling, 20% for commercial refrigeration, 30% for industrial process). If the measured leak rate is below the threshold (below 30% for industrial process refrigeration), repair is not immediately required, though continued monitoring is necessary.
EPA 608 Type III Practice Test 3
Which refrigerant is the primary replacement for R-11 in new low-pressure centrifugal chillers?