EPA 608 Type III practice questions

Question 1

Which refrigerants are used in low-pressure appliances?

Accepted Answer

R-11 and R-123. Low-pressure appliances (mostly centrifugal chillers) use R-11, R-123, R-113 or R-245fa: saturation pressure below 45 psia at 104°F.

Question 2

Under normal operation, the evaporator of a low-pressure chiller runs:

Accepted Answer

Below atmospheric pressure (in a vacuum). Because the low side is in a vacuum, leaks pull air and moisture INTO the system instead of letting refrigerant out.

Question 3

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

Accepted Answer

To remove air and other noncondensables from the system. Air leaks into the low-pressure side and collects at the top of the condenser. The purge unit removes it.

Question 4

Where does the purge unit take its suction from?

Accepted Answer

The top of the condenser. Noncondensables are trapped at the top of the condenser, so the purge unit draws from there.

Question 5

Excessive purge unit operation is a sign of:

Accepted Answer

A leak that is letting air into the system. If the purge runs a lot, air is leaking in. Find and fix the leak.

Question 6

What is the required recovery level for a low-pressure appliance, using equipment made after Nov 15, 1993?

Accepted Answer

25 mm Hg absolute. 40 CFR 82.156 Table 1: low-pressure appliances = 25 mm Hg absolute with recovery equipment made before or after Nov 15, 1993. That is about 29 in. Hg vacuum on a gauge. (Older study guides list 25 in. Hg for pre-1993 equipment.)

Question 7

For a NON-major repair on a low-pressure appliance, it must be pressurized to no higher than:

Accepted Answer

0 psig. Instead of evacuating, a low-pressure appliance is raised to atmospheric pressure (0 psig) for a non-major repair.

Question 8

Which methods are allowed to raise the pressure of a low-pressure system for a non-major repair?

Accepted Answer

Controlled hot water or a built-in heating device such as Prevac. Heat raises the refrigerant pressure without adding gas that would later need to be purged.

Question 9

For refrigerants that boil at or below 85°F (like R-123), may nitrogen be used to raise the pressure for a repair?

Accepted Answer

No; methods that need later purging, like nitrogen, are not allowed. 40 CFR 82.156(a)(1)(ii): for refrigerants boiling at or below 85°F, do not use nitrogen. For refrigerants boiling above 85°F, heat first, then nitrogen may finish raising pressure to atmospheric.

Question 10

What is the preferred order for pressurizing a low-pressure system for a leak test?

Accepted Answer

Hot water or a heating device (like Prevac) first, then nitrogen. Using the refrigerant's own vapor pressure (by heating) is preferred; nitrogen is the next option.

Question 11

What is the maximum leak test pressure for a low-pressure centrifugal chiller?

Accepted Answer

10 psig. Do not exceed 10 psig: the rupture disc on the evaporator typically bursts at 15 psig.

Question 12

At what pressure does the rupture disc on a low-pressure chiller evaporator typically open?

Accepted Answer

15 psig. The rupture disc protects the shell from over-pressure and is typically set at 15 psig.

Question 13

What is the high-pressure cut-out setting of a recovery device used on low-pressure appliances?

Accepted Answer

10 psig. The recovery unit's high-pressure cut-out is set at 10 psig, below the 15 psig rupture disc.

Question 14

Why should the water in a chiller be circulated (or drained) during refrigerant evacuation?

Accepted Answer

To prevent the water in the tubes from freezing. As pressure drops, the refrigerant temperature drops below freezing and can freeze and burst the water tubes.

Question 15

Before draining oil from a low-pressure chiller, the oil should be heated to:

Accepted Answer

130°F. Heating the oil to 130°F drives out dissolved refrigerant so less is released with the oil.

Question 16

When recovering from a low-pressure chiller, what should be recovered first?

Accepted Answer

The liquid. Remove the liquid first (it is most of the charge), then recover the remaining vapor.

Question 17

After the liquid is removed from a large low-pressure chiller, why must the vapor also be recovered?

Accepted Answer

A large chiller can hold many pounds of refrigerant as vapor. Even after liquid removal, the vapor in a big shell can amount to a lot of refrigerant (on the order of 100 lb in very large chillers).

Question 18

When recharging a low-pressure chiller that is in a deep vacuum, what should be introduced first?

Accepted Answer

Vapor. Charging vapor first raises the pressure above the point where water in the tubes would freeze. Then switch to liquid.

Question 19

Through which valve should a centrifugal chiller be charged?

Accepted Answer

The evaporator charging valve. Centrifugals are charged through the evaporator charging valve (low point of the evaporator).

Question 20

After reaching the required recovery vacuum on a low-pressure appliance, why wait a few minutes?

Accepted Answer

If the pressure rises, refrigerant is still in the system or the oil. A pressure rise means liquid refrigerant or refrigerant in the oil is still boiling off. Continue recovery.

Question 21

Under ASHRAE Standard 15, an equipment room with an R-123 chiller must have:

Accepted Answer

A refrigerant sensor (monitor) for R-123. R-123 is more toxic than many refrigerants, so a refrigerant-specific sensor with alarm and ventilation is required.

Question 22

What is required in every mechanical equipment room under ASHRAE 15, no matter which refrigerant?

Accepted Answer

An oxygen deprivation sensor (or refrigerant monitor). All refrigerants can displace oxygen, so the room needs a sensor with an alarm.

Question 23

What is the leak rate threshold for a low-pressure COMFORT COOLING chiller with 50 lb or more of ODS refrigerant?

Accepted Answer

10% per year. Same leak rates as other appliance types: comfort cooling 10%, commercial refrigeration 20%, industrial process refrigeration 30%.

Question 24

If a chiller exceeds the allowed leak rate, it must be repaired within:

Accepted Answer

30 days (120 days if an industrial process shutdown is needed). 40 CFR 82.157(d): repair within 30 days of the refrigerant addition, or 120 days if an industrial process shutdown is required.

Question 25

An appliance that leaks 125% or more of its full charge in one calendar year must be:

Accepted Answer

Reported to EPA by March 1 of the following year. Chronically leaking appliances (50 lb or more) need a report describing the leak repair efforts.

Question 26

Which repair on a chiller is a MAJOR repair?

Accepted Answer

Removing the condenser or evaporator. Major = removing the compressor, condenser, evaporator or auxiliary heat exchange coil, or uncovering more than 4 sq. in. of flow area for more than 15 minutes.

Question 27

Why does a leak in a low-pressure chiller cause the refrigerant to become contaminated?

Accepted Answer

Air and moisture are drawn in because the system runs in a vacuum. Moisture with refrigerant forms acids that damage the motor and metals. That is why leaks must be found quickly.

Question 28

R-123 boils at about what temperature at atmospheric pressure?

Accepted Answer

About 82°F. R-123 boils at about 82°F (R-11 at about 75°F), so at room temperature it is close to atmospheric pressure.

Question 29

Which certification is required to service a centrifugal chiller that uses R-123?

Accepted Answer

Type III (or Universal). Low-pressure appliances require Type III certification.

Question 30

Why is a pressure-temperature (PT) chart useful on a low-pressure chiller?

Accepted Answer

Comparing saturation pressure with temperature shows noncondensables or the wrong refrigerant. If the condenser pressure is higher than saturation pressure for its temperature, air is present.

EPA 608 Type III Practice Test – Low-Pressure Chillers