Electricity Unit 14 Review

A heating and cooling system will operate properly using jumper wires to manually complete the control circuits at the low-voltage thermostat, but the system will not operate with the jumper wires removed, the _______________ is the likely cause of the malfunction.

• Control transformer

• Thermostat

• Contactor

• Control wiring

A motor with a rating of 15 full load amps is protected by a line voltage overload that keeps opening at a current draw of 14 amps, indicating the overload is ___________.

• Good

• Shorted

• Weak

• Too large for the motor

A reading of line voltage across the contacts of a sequencer indicates the contacts are _______________.

• Open

• Shorted

• Closed

• None of the choices are correct

An electric heating system controlled by a sequencer is not heating. If the technician reads 240 volts across each contact of the sequencer and zero volts across the sequencer element, which of the following is likely the cause of the malfunction?

• The sequencer contacts are stuck open

• The thermostat is not sending 24 volts to the sequencer element

• The sequencer element is open

• The sequencer contacts are stuck closed

For a technician to determine if a pressure switch is faulty, the technician needs to know __________________.

• The function of the pressure switch

• The pressure settings of the switch

• The pressure in the refrigeration system

• All of the choices are correct

Motors are very important loads in heating, cooling, and refrigeration equipment because they are used to rotate ___________________.

• Fans

• Compressors

• Pumps

• All of the choices are correct

The internal overload used on most modern single-phase hermetic compressors is in the _____________ terminal of the motor.

• Common

• Run

• Start

• All of the choices are correct

What can a technician use to interpret the meaning of the flashing light codes given by the LED on an integrated furnace control board?

• Integrated furnace diagnostic module

• Diagnostic code legend found on the furnace or online from the manufacturer

• Wiring schematic diagram

• All of the choices are correct

What can help a technician troubleshoot and diagnose problems associated with a gas furnace using electronic controls?

• Chart showing the normal operating sequence

• Troubleshooting chart

• Wiring schematic diagram

• All of the choices are correct

What is a method of checking the flame rectification circuit to sense the flame in gas furnaces?

• Check for DC microvolts using a voltmeter

• Check for DC microamps by placing a microammeter in series with the flame rod or system ground

• Check for DC amps by placing the amp-on ammeter around the wire to the flame rod

• Check to see if 24 volts is being supplied to the flame sensor using an AC voltmeter