Air Conditioning Repair Installation and Evacuation Procedures Questions and Answers

Question 1

What is the primary purpose of flowing a small amount of dry nitrogen through the copper tubing while brazing a line set during an AC installation?

Accepted Answer

To prevent the formation of copper oxide scale inside the tubing

Answer

To cool the joint rapidly for a stronger bond

Answer

To increase the internal pressure, forcing the brazing alloy into the joint

Answer

To purge any residual refrigerant from the new line set

Question 2

A technician is performing an evacuation on a newly installed system. After isolating the vacuum pump, the technician observes the vacuum level rises from 400 microns and stabilizes at 1,500 microns. What is the most likely cause of this behavior?

Accepted Answer

Moisture is still present and boiling off within the system

Answer

A large leak in the flare connections

Answer

A faulty micron gauge giving an incorrect reading

Answer

The vacuum pump oil needs to be changed

Question 3

To ensure the most accurate reading of the system's vacuum level, where should the micron gauge be placed?

Accepted Answer

As far away from the vacuum pump as possible within the system

Answer

Directly on the vacuum pump inlet port

Answer

On the center port of the charging manifold

Answer

On the high-pressure side service valve only

Question 4

During a new split-system installation, which of the following practices is critical for ensuring proper oil return to the compressor and preventing liquid slugging, especially with long line sets?

Accepted Answer

Ensuring the suction line is fully insulated and properly supported

Answer

Ensuring the liquid line is insulated along its entire length

Answer

Using a pipe bender to create sharp 90-degree turns

Answer

Installing the suction line with a continuous downward slope from the evaporator to the condenser

Question 5

When pressure testing a new R-410A system for leaks, what is the appropriate substance and procedure?

Accepted Answer

Pressurize with dry nitrogen to a pressure recommended by the manufacturer, typically around 250-450 PSIG.

Answer

Pressurize with compressed shop air to 100 PSIG, as it is readily available and inexpensive.

Answer

Introduce a small amount of R-410A and then pressurize with oxygen to make leaks easier to find.

Answer

Pressurize with dry nitrogen to the system's operating pressure as listed on the data plate.

Question 6

Which of the following setup combinations will achieve the fastest and most thorough evacuation of a refrigeration system?

Accepted Answer

A 2-stage vacuum pump with large diameter (3/8" or 1/2") hoses and Schrader core removal tools.

Answer

A 2-stage vacuum pump with standard 1/4" charging hoses connected to the service ports.

Answer

A single-stage vacuum pump with 3/8" hoses and the Schrader cores left in place.

Answer

A 2-stage vacuum pump with 1/4" hoses connected directly to the service valves, bypassing the manifold.