Question 1

What type of appliances are covered by Type III certification?

Accepted Answer

Type III certification covers the maintenance, service, repair, and disposal of low-pressure appliances, such as centrifugal chillers.

Question 2

Which refrigerant is typically used in low-pressure chillers?

Accepted Answer

R-123 is a common HCFC refrigerant used in low-pressure centrifugal chillers. (Older units used R-11).

Question 3

What is the primary purpose of a purge unit on a low-pressure chiller?

Accepted Answer

Since low-pressure systems operate in a vacuum, air and moisture can leak IN. The purge unit runs to separate and remove these non-condensables from the refrigerant.

Question 4

At what pressure does the rupture disc on a low-pressure centrifugal chiller typically burst?

Accepted Answer

The rupture disc is a safety relief device set to burst at 15 psig to prevent over-pressurization of the low-pressure vessel.

Question 5

Where does air and moisture usually enter a low-pressure system?

Accepted Answer

Because low-pressure systems operate below atmospheric pressure (in a vacuum), leaks pull air and moisture INTO the system rather than pushing refrigerant out.

Question 6

When leak testing a low-pressure centrifugal with nitrogen, what is the maximum test pressure?

Accepted Answer

You must not exceed 10 psig when pressurizing a low-pressure system, as the rupture disc will burst at 15 psig.

Question 7

What is the required recovery vacuum level for a Type III appliance using recovery equipment manufactured after Nov 15, 1993?

Accepted Answer

For Type III appliances, the required recovery level is 25 mm Hg absolute pressure (which is a deeper vacuum than 25 inches Hg).

Question 8

When recovering liquid refrigerant from a chiller, you should remove liquid from the:

Accepted Answer

Liquid settles at the bottom. Recovering from the lowest access point (often the evaporator or condenser drain) ensures you get the liquid first.

Question 9

After removing the liquid refrigerant, what must be done next?

Accepted Answer

After liquid recovery, significant vapor remains. You must recover the vapor to the required vacuum level (25 mm Hg absolute) before opening the system.

Question 10

Why should you circulate water through the chiller bundles during refrigerant recovery?

Accepted Answer

As refrigerant boils off during recovery, it absorbs heat, potentially freezing the water in the heat exchanger tubes. Circulating water prevents this freezing.

Question 11

To raise the pressure of a low-pressure system for leak detection without using nitrogen, you can:

Accepted Answer

Heating the refrigerant (using warm water or heating blankets) raises the system pressure naturally, allowing leaks to be found without introducing nitrogen.

Question 12

A hydrostatic tube test kit is used to:

Accepted Answer

A hydrostatic tube test kit determines if a specific tube in the heat exchanger is leaking.

Question 13

What is the maximum leak rate allowed for 'Comfort Cooling' chillers containing 50 lbs or more of refrigerant?

Accepted Answer

Comfort cooling appliances (like chillers for AC) have a 10% annual leak rate threshold.

Question 14

High-efficiency purge units are designed to:

Accepted Answer

Modern high-efficiency purge units separate air from refrigerant more effectively, minimizing the amount of refrigerant vented with the air.

Question 15

When recharging a low-pressure system, you should introduce vapor first until the pressure reaches 16.9 inches Hg vacuum (saturation temp of 32°F) to prevent:

Accepted Answer

If liquid refrigerant is added into a deep vacuum, it will boil instantly, dropping the temperature below 32°F and freezing the water in the tubes. Vapor is added first to raise the pressure/temperature above freezing.

Question 16

ASHRAE Standard 15 requires that a machine room with a chiller must have:

Accepted Answer

ASHRAE 15 mandates a refrigerant sensor that activates an alarm and ventilation system if a leak is detected.

Question 17

If you suspect a leak in the water box of a chiller, you should:

Accepted Answer

Place the leak detector probe in the drain valve opening or check the water for refrigerant presence.

Question 18

The rupture disc on a low-pressure chiller is connected to:

Accepted Answer

The rupture disc is typically mounted on the evaporator or condenser shell to relieve excess pressure.

Question 19

When recovering refrigerant from a system with a major leak, you are only required to evacuate to:

Accepted Answer

If a leak makes it impossible to reach the deep vacuum levels, you evacuate to 0 psig to prevent pulling air into the recovery tank.

Question 20

Excessive running of the purge unit generally indicates:

Accepted Answer

The purge unit's job is to remove air. If it runs frequently, it means air is constantly entering the system through a leak.

Question 21

Before disposing of a low-pressure appliance, the refrigerant must be recovered to:

Accepted Answer

Disposal requires the same evacuation level as repair: 25 mm Hg absolute.

Question 22

Type III appliances typically use which type of compressor?

Accepted Answer

Low-pressure systems are almost exclusively large centrifugal chillers.

Question 23

When charging liquid refrigerant into a low-pressure system, the system pressure should be at least:

Accepted Answer

This corresponds to a saturation temperature of 36°F for R-123 (or 32°F generally), ensuring water won't freeze when liquid hits the tubes.

Question 24

If you are using a water-cooled recovery unit, you must:

Accepted Answer

Water left in the recovery unit condenser can freeze and burst the tubes if the unit is stored in a cold area or if recovery lowers the temperature significantly.

Question 25

What is the boiling point of R-11 at atmospheric pressure?

Accepted Answer

R-11 boils at approx 75°F. This is why it stays liquid at room temperature in an open container (though it evaporates).

Question 26

A chiller's rupture disc vents the refrigerant to:

Accepted Answer

The discharge from a rupture disc must be piped outdoors to prevent filling the machine room with toxic/asphyxiating gas.

Question 27

During evacuation of a system with large amounts of water, it may be necessary to:

Accepted Answer

Heating the system helps boil off the water and prevents it from freezing into ice, which would stop the dehydration process.

Question 28

Which test is used to determine if a tube is leaking?

Accepted Answer

While eddy current tests check wall thickness, a hydrostatic test (pressurizing the tube) confirms if it leaks.

Question 29

For a low-pressure system, the high-pressure cut-out control is typically set to:

Accepted Answer

The cut-out is set to 10 psig to shut down the compressor before the rupture disc blows at 15 psig.

Question 30

If you are repairing a leak in a chiller and you add 100 lbs of refrigerant, you must:

Accepted Answer

Any time refrigerant is added to a regulated appliance (≥50 lbs), the leak rate must be calculated to determine compliance with leak repair regulations.

Question 31

What is the definition of a 'Refrigerant Monitor'?

Accepted Answer

A refrigerant monitor senses refrigerant vapor in the machinery room air and triggers alarms/ventilation.

Question 32

When pressurizing a low-pressure system with nitrogen for a leak check, you should:

Accepted Answer

Exceeding 10 psig risks blowing the rupture disc (15 psig setting).

Question 33

In a low-pressure chiller, the purge unit takes its suction from the:

Accepted Answer

Air and non-condensables collect at the top of the condenser (highest point, coolest gas), so the purge unit draws from there.

Question 34

Which of the following safety precautions should be followed for low-pressure systems?

Accepted Answer

Standard safety protocols apply: PPE, ventilation, and safe handling.

Question 35

Under EPA regulations, an 'Initial Verification Test' is required:

Accepted Answer

An Initial Verification Test under EPA regulations is performed after the repair is completed but before the system is recharged or repressurized with refrigerant. This timing allows the technician to confirm that all repaired leak points are sealed before refrigerant is reintroduced. A Follow-up Verification Test is performed after the system has been recharged and returned to normal operating conditions.

Question 36

A typical advantage of low-pressure chillers is:

Accepted Answer

Centrifugal chillers (low pressure) are known for high efficiency in large cooling applications.

Question 37

When removing oil from a low-pressure system, the oil should be heated to:

Accepted Answer

Heating oil to 130°F helps release dissolved refrigerant, reducing the amount of refrigerant disposed of with the oil.

Question 38

If a low-pressure appliance is converted to a high-pressure refrigerant, the rupture disc must be:

Accepted Answer

High-pressure refrigerants operate well above 15 psig. The rupture disc must be replaced with a relief valve rated for the new design pressure.

Question 39

According to ASHRAE Standard 15, the use of a room sensor and alarm is required for:

Accepted Answer

ASHRAE 15 requires sensors for all refrigerant safety groups (A1, B1, etc.) in machinery rooms.

Question 40

A 'Controlled Hot Water' method for pressurization uses:

Accepted Answer

Hot water is used to warm the refrigerant and raise pressure for leak checking, but it must be controlled so pressure doesn't pop the rupture disc.

Question 41

Identify the low-pressure refrigerant from the list below:

Accepted Answer

R-123 is the standard low-pressure replacement for R-11.

Question 42

The maximum test pressure for leak testing a low-pressure chiller with nitrogen is:

Accepted Answer

10 psig is the safe limit to avoid bursting the 15 psig rupture disc.

Question 43

After recovering the liquid, about how much refrigerant vapor remains in a 350-ton R-123 chiller?

Accepted Answer

A significant amount of refrigerant (approx 100 lbs in a large machine) remains as vapor after liquid recovery, which is why vapor recovery is mandatory.

Question 44

When should the water pumps be turned on during recovery?

Accepted Answer

Pumps should run to keep water moving through the tubes, preventing localized freezing as refrigerant boils off.

Question 45

Recovery of refrigerant from a low-pressure appliance must start with:

Accepted Answer

Always recover liquid first to reduce the volume quickly, then switch to vapor recovery.

Type III (Low-Pressure) Practice Questions

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