EPA 608 Type III Practice Test 3

Question 1

Which refrigerant is the primary replacement for R-11 in new low-pressure centrifugal chillers?

Accepted Answer

R-123

Answer

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?

Accepted Answer

Supplied air respirator or SCBA when entering confined spaces where concentrations may exceed exposure limits

Answer

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?

Accepted Answer

Increasing system leak rate allowing more air infiltration

Answer

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?

Accepted Answer

Air can infiltrate through mechanical seals when the compressor stops and system pressure equilibrates below atmospheric

Answer

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?

Accepted Answer

Centrifugal compressors raise refrigerant pressure using rotating impellers (kinetic energy); reciprocating compressors use pistons (positive displacement)

Answer

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.

EPA 608 609 Practice Test

EPA 608 609 Practice Test

EPA 608 Type III Practice Test 3