313D System Installation and Maintenance 3

Question 1

What does a micron gauge measure during the evacuation of an air conditioning system?

Accepted Answer

Absolute pressure in the system

Answer

A micron gauge measures absolute pressure in microns of mercury (µm Hg), allowing technicians to verify that the system has been evacuated to an acceptable vacuum level.

Question 2

A residential AC system is short-cycling on high pressure. Which maintenance action should the technician perform FIRST?

Accepted Answer

Check and clean the condenser coil for blockage or dirt

Answer

A dirty or blocked condenser coil reduces heat rejection, causing high-side pressure to rise and the system to trip on the high-pressure limit.

Question 3

When performing a seasonal startup on a residential central air system, which task should be completed BEFORE energizing the system?

Accepted Answer

Checking the disconnect and inspecting wiring for damage

Answer

Before energizing any system at startup, technicians must inspect the disconnect, electrical connections, and wiring to identify any damage that could cause a hazardous condition.

Question 4

A crankcase heater on a residential compressor is used primarily for what purpose?

Accepted Answer

To prevent refrigerant migration and liquid slugging during the off cycle

Answer

The crankcase heater keeps the compressor oil warm during the off cycle to prevent refrigerant from migrating into and mixing with the compressor oil, which could cause liquid slugging on startup.

Question 5

When installing ductwork for a new residential AC system, what is the purpose of using mastic sealant instead of standard duct tape?

Accepted Answer

Mastic provides a durable, long-lasting airtight seal that duct tape cannot maintain over time

Answer

Mastic sealant creates a permanent, flexible, airtight bond at duct joints, whereas standard duct tape degrades and loses adhesion over time, allowing air leaks.

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

313D System Installation and Maintenance 3