313D System Installation and Startup Questions and Answers

Question 1

During a new split system installation, the technician notes the liquid line is 3/8" and the suction line is 7/8".
The line set length is 50 feet.
The manufacturer's instructions state the outdoor unit comes pre-charged for a 15-foot line set.
What is the most critical next step for the technician regarding the refrigerant charge?

Accepted Answer

Add a calculated amount of refrigerant based on the additional line set length and diameter.

Answer

Release the factory charge and allow the system to run for 30 minutes before checking pressures.

Answer

Recover the factory charge and weigh in a new charge based on the nameplate value only.

Answer

Assume the factory charge is sufficient for the longer line set length.

Question 2

A technician is performing a deep vacuum evacuation on a newly installed residential air conditioning system. After achieving a vacuum of 400 microns, the technician isolates the system from the vacuum pump. The micron gauge reading slowly rises and then stabilizes at 1,500 microns. What does this indicate?

Accepted Answer

The system is leak-free but still contains moisture.

Answer

There is a small leak in the system.

Answer

The vacuum pump oil is contaminated and needs to be changed.

Answer

The micron gauge is faulty and requires calibration.

Question 3

Which of the following is a critical reason for installing a P-trap at the base of a long vertical suction line riser in a split-system air conditioner installation?

Accepted Answer

To ensure proper oil return to the compressor.

Answer

To prevent liquid refrigerant from flooding the evaporator coil on startup.

Answer

To reduce unwanted noise and vibration during operation.

Answer

To provide a location for future system access and service.

Question 4

During the commissioning of a new residential AC system with a TXV metering device, which charging method provides the most accurate results and is recommended by most manufacturers?

Accepted Answer

Subcooling method, measured at the liquid line service valve.

Answer

Superheat method, based on indoor wet-bulb and outdoor dry-bulb temperatures.

Answer

Feeling the suction line temperature by hand to ensure it is 'beer can cold'.

Answer

Setting pressures to a standard chart without considering temperatures.

Question 5

A technician is installing a new condensing unit on an unlevel gravel bed. What is the proper first step to ensure long-term reliability of the unit?

Accepted Answer

Pour a new, level concrete pad or install a high-impact plastic pad.

Answer

Use shims to level the existing gravel bed before placing the unit.

Answer

Proceed with the installation as the unit's internal components can handle a slight angle.

Answer

Place wooden blocks under the unit's feet to achieve a level position.

Question 6

Which of the following documents is essential for determining the correct equipment size and capacity for a new residential air conditioning installation?

Accepted Answer

A Manual J load calculation report.

Answer

The local building permit application.

Answer

The homeowner's previous utility bills.

Answer

The manufacturer's warranty registration form.