313D Electrical Systems and Controls 3

Question 1

A residential AC system uses a dual run capacitor. Which terminals are typically labeled on this component?

Accepted Answer

C (common), FAN, HERM

Answer

L1, L2, and ground

Answer

Start, run, and common

Answer

High, low, and neutral

Question 2

What is the function of a hard start kit (potential relay and start capacitor) added to an existing AC compressor?

Accepted Answer

Increase starting torque to help the compressor start under difficult conditions

Answer

Reduce running amperage during normal operation

Answer

Replace the dual run capacitor permanently

Answer

Provide overcurrent protection to the compressor

Question 3

An ECM blower motor in a residential air handler is different from a PSC motor because it:

Accepted Answer

Uses a variable-speed DC motor controlled by an integrated module

Answer

Requires a larger run capacitor

Answer

Operates on 24V DC only

Answer

Cannot be used with variable refrigerant flow systems

Question 4

When using a clamp-on ammeter to measure compressor current, you clamp around only one power conductor. Why?

Accepted Answer

To measure the current in one leg without cancellation from opposing current flow

Answer

To avoid damaging the meter at high amperage

Answer

Because the other conductor carries 24V control voltage

Answer

Both conductors must be clamped for accurate readings

Question 5

A high-pressure switch in a residential AC system is wired in series with the:

Accepted Answer

Compressor contactor coil circuit

Answer

Condenser fan motor run capacitor

Answer

Indoor blower relay

Answer

Low-voltage transformer primary

Question 6

What reading would indicate a shorted run capacitor when tested with a capacitance meter?

Accepted Answer

Reading of 0 µF or OL (overload/short)

Answer

Reading slightly above the rated µF value

Answer

Reading significantly below the rated µF value

Answer

Infinite resistance reading

Question 7

In residential AC electrical schematics, a dashed line between two components typically indicates:

Accepted Answer

A mechanical linkage or shared enclosure

Answer

A high-voltage conductor

Answer

A ground wire

Answer

A field-installed wire by the installer