313D Electrical Schematics and Controls 4

Question 1

What is the purpose of a transformer in the residential AC control circuit?

Accepted Answer

To step down 240V line voltage to 24V for the low-voltage control circuit

Answer

The control transformer steps down 240V (or 120V) line voltage to 24V AC, which powers the thermostat and control circuit components safely.

Question 2

A run capacitor shown in a schematic is connected in series with which motor winding?

Accepted Answer

Start winding (auxiliary winding)

Answer

The run capacitor is wired in series with the start (auxiliary) winding to create a phase shift that maintains running torque and efficiency in single-phase motors.

Question 3

When reading a pictorial wiring diagram, a wire shown going to a splice or junction with a dot indicates:

Accepted Answer

An electrical connection between crossing or meeting wires

Answer

A solid dot at a wire junction on a schematic indicates an electrical connection is made at that point, as opposed to wires that cross without a dot (no connection).

Question 4

In a residential AC system, the 'G' terminal on the thermostat controls:

Accepted Answer

The indoor blower fan relay

Answer

The G terminal sends a 24V signal to energize the indoor blower fan relay, allowing the fan to run independently for ventilation without calling for cooling or heating.

Question 5

What does a solid triangle or arrow symbol on a schematic pointing into a wire or component indicate?

Accepted Answer

Direction of conventional current flow or signal direction

Answer

An arrow or triangle on a schematic indicates the direction of conventional current flow or the direction of a signal, helping trace circuit operation.

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

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

313D Electrical Schematics and Controls 4