Air Conditioning Repair Installation and Service Procedures 5

Question 1

During a system commissioning, the technician measures a wet-bulb temperature of 67°F entering the evaporator and a dry-bulb of 75°F. What is the approximate entering relative humidity?

Accepted Answer

About 55%

Answer

A 67°F wet-bulb with 75°F dry-bulb corresponds to approximately 55% relative humidity, which is typical summer indoor design conditions.

Question 2

What is the most common cause of a newly installed air handler producing excessive noise at startup?

Accepted Answer

Blower wheel set screw not tightened or wheel rubbing the housing

Answer

A loose blower wheel set screw allows the wheel to wobble or shift, causing scraping or rattling noise that disappears once the set screw is properly torqued.

Question 3

When charging a system by weight, the technician should zero the refrigerant scale:

Accepted Answer

Before connecting the hose, with the empty hose weight accounted for

Answer

Zeroing the scale with the hose already attached accounts for the hose weight, so the display shows only the refrigerant transferred rather than hose plus refrigerant.

Question 4

A condensing unit is located in a pit below grade level. What is the primary concern with this installation?

Accepted Answer

Hot air discharge will recirculate into the unit, reducing efficiency and capacity

Answer

A condensing unit in a below-grade pit tends to trap its own hot discharge air, causing high head pressure, reduced efficiency, and potential high-pressure lockout.

Question 5

After replacing a TXV on an R-410A system, the technician finds the superheat is 25°F instead of the target 10°F. What is the most likely cause?

Accepted Answer

The TXV sensing bulb is not properly clamped to the suction line

Answer

An improperly secured TXV sensing bulb reads ambient temperature instead of suction line temperature, causing the valve to restrict flow and drive up superheat.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

Air Conditioning Repair Installation and Service Procedures 5