NATE Electrical and Controls 2

Question 1

A contactor coil is rated at 24V AC. If the supply voltage to the coil drops to 18V AC, what is the MOST likely result?

Accepted Answer

The contactor may chatter or fail to fully close

Answer

The contactor operates normally

Answer

The contactor coil burns out immediately

Answer

The contactor opens the circuit

Question 2

What is the function of a run capacitor in a PSC (permanent split capacitor) motor?

Accepted Answer

Improve power factor and running efficiency

Answer

Provide starting torque only

Answer

Protect against overcurrent

Answer

Store energy during power outages

Question 3

What does a lockout/tagout (LOTO) procedure require before servicing electrical HVAC equipment?

Accepted Answer

Isolating and de-energizing the power source and verifying zero energy state

Answer

Lowering thermostat setpoint to off

Answer

Wearing rubber-soled shoes

Answer

Switching the system to cooling mode

Question 4

On a cooling thermostat, which terminals are energized when the system is calling for cooling?

Accepted Answer

R and Y

Answer

R and W

Answer

R and G

Answer

R and O

Question 5

What does a megohmmeter (megger) measure?

Accepted Answer

Insulation resistance of motor windings

Answer

AC line frequency

Answer

Capacitor microfarad rating

Answer

Contactor coil impedance

Question 6

Which type of transformer is commonly used to step down 240V line voltage to 24V for HVAC control circuits?

Accepted Answer

Step-down isolation transformer

Answer

Autotransformer

Answer

Current transformer

Answer

Step-up transformer

Question 7

A motor draws 8 amps at 240V. What is the approximate power consumption in watts?

Accepted Answer

1,920 watts

Answer

1,200 watts

Answer

960 watts

Answer

2,400 watts