Electrical Controls

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Question 1

A fuse is used in an electrical circuit to

A	Protect the inductive load from an over current condition.
B	Protect against a ground fault condition
C	Protect the circuit wires from an over current condition
D	Protect against open circuits

Question 2

How are fuses rated?

A	In amps only
B	In volts only
C	In amps with a minimum voltage rating
D	In amps with a maximum voltage rating

Question 3

What will an ohmmeter measure when testing an open fuse?

A	Zero resistance
B	Infinite resistance
C	Measurable resistance
D	Continuity

Question 4

What type of sensing element is commonly found in fan and limit controls?

A	Copper
B	Helical invar
C	Bimetal
D	Mercury

Question 5

What is used to sense space temperature in electronic temperature controls?

A	Resistors
B	Transistors
C	Capacitors
D	Thermistors

Question 6

What is known about a liquid charged remote type temperature control?

A	Its bulb is both extremely sensitive and completely full of liquid
B	Its bulb is extremely sensitive, has some gas present, and always has liquid present
C	Its bulb is not extremely sensitive and is completely full of liquid
D	Its bulb is not extremely sensitive, has some gas present, and always has liquid present

Question 7

When installing_____________, its sensing bulb must always be the coldest part of the control.

A	The gas charged remote temperature control
B	The cross charged remote temperature control
C	The liquid charged remote temperature control
D	The bimetal type temperature control

Question 8

A temperature control that uses a positive temperature coefficient thermistor (PTCT)

A	Decreases resistance as temperature increases
B	Increases resistance as temperature increases
C	Must be level for proper operation
D	Must be installed near a supply air register for proper operation

Question 9

A heating thermostat

A	Opens on a drop in temperature
B	Opens on a rise in temperature
C	Energizes a heating system when its setpoint is below space temperature
D	De energizes a heating system when its setpoint is above space temperature

Question 10

The heat anticipator

A	Must be energized when the system is de- energized
B	Controls system lag
C	Controls system overshoot
D	Is wired in parallel with the heating thermometer

Question 11

When adjusting a heat anticipator on a thermostat

A	The heating and cooling control amperage must be measured
B	The heating and cooling control voltage must be measured
C	The cooling control amperage must be measured
D	The heating control amperage must be measured

Question 12

Choose the correct color code an its circuit for a heating and cooling thermostat

A	Red-heating circuit, yellow-cooling circuit, white-power source, green-fan relay
B	Red-fan relay, yellow-power source, white-heating circuit, green-cooling circuit
C	Red-power source, yellow-heating circuit, white-cooling circuit, green-fan relay
D	Red-power source, yellow-cooling circuit, white-heating circuit, green-fan relay

Question 13

How may wires does a two stage heating and two stage cooling thermostat commonly use?

A	4
B	6
C	8
D	10

Question 14

What is the purpose of automatic changeover on a heating and cooling thermostat?

A	It automatically changes the thermostat’s set point
B	It automatically changes the thermostat’s anticipation value
C	It automatically changes from heating to cooling
D	It automatically changes from first stage heating to second stage heating

Question 15

What is the definition of deadband?

A	Deadband is the point at which the thermostat is satisfied when in the heating cycle
B	Deadband is the point at which the thermostat is satisfied when in the cooling cycle
C	Deadband is the point at which the thermostat is satisfied when in the automatic cycle
D	Deadband is the point at which the thermostat is satisfied between stages when using a two stage thermostat

Question 16

An outdoor thermostat that is used on an electric heating system is commonly used to

A	Energize electric heaters if the outdoor temperature drops below a predetermined temperature
B	De energize the system if the temperature rises above a predetermined temperature
C	Switch the system to emergency heat if the temperature drops below a predetermined temperature
D	Energize electric heaters if the outdoor temperature rises above a predetermined temperature

Question 17

A cooling thermostat

A	Opens on a drop in temperature
B	Opens on a rise in temperature
C	Energizes a cooling system when its set point is above space temperature
D	De energizes a cooling system when its set point is below space temperature

Question 18

A cooling anticipator

A	Must be de energized when the system is de energized
B	Controls system lag
C	Controls system overshoot
D	Is wired in series with the cooling thermostat

Question 19

Outdoor thermostats are used on air conditioning systems to

A	Prevent short cycling of the compressor during the peak season
B	Prevent short cycling of the heating system during the air conditioning season
C	De energize the compressor during low ambient conditions
D	Energize the condenser fans during low ambient conditions

Question 20

What type of sensing element is the most accurate?

A	A helical bimetal
B	A refrigerant filled sensing element
C	A snap disc bimetal
D	A thermistor

Question 21

What type of sensing element is used in a programmable thermostat?

A	A Resistor
B	A Thermistor
C	. A Transistor
D	A Bi metal

Question 22

What is known about the anticipators that are located on a programmable thermostat?

A	The heating has a fixed setting and the cooling can either be fixed or adjustable
B	. The heating either has a fixed setting or can be adjustable and the cooling has fixed setting
C	The heating has a fixed setting only and the cooling has a fixed setting
D	The heating has a fixed setting only and the cooling is adjustable

Question 23

When using a heat pump type programmable thermostat, what cycle commonly uses an LED light?

A	The heating cycle
B	The cooling cycle
C	The emergency heat cycle
D	The first and second stage heating and cooling cycles

Question 24

When installing a programmable thermostat, what extra low voltage wire is commonly added to the circuit?

A	A second power supply wire
B	The emergency heat circuit
C	The secondary blower circuit
D	The common from the transformer

Question 25

How does a two stage thermostat control a heat pump during the heating cycle?

A	. The compressor is controlled by the first stage, and the auxiliary heaters are controlled by the second stage
B	The auxiliary heaters are controlled by the first stage, and the compressor is controlled by the second stage
C	The compressor and the auxiliary heaters are controlled by the first stage, and the gas fired system is controlled by the second stage
D	. The gas fired system is controlled by the first stage, and the compressor and auxiliary heaters are controlled by the second stage

Question 26

What is a battery used for on a programmable thermostat?

A	. To energize the thermostat’s LED lights
B	To control the automatic changeover cycle
C	. To save the system’s program if there is a loss of power
D	To energize the heat and cool anticipators

Question 27

When using a programmable thermostat, what is “temperature setback”?

A	It is the temperature setting of the thermostat during an occupied time
B	It is the temperature setting of the thermostat during an unoccupied
C	It is the point at which the temperature set point of the thermostat is between the heating and cooling cycle
D	It is the point at which the thermostat’s anticipation rate is set lower than the actual system current draw

Question 28

What is meant by the term intelligent recovery?

A	It is the feature that calculates the room temperature every 2 to 3 hrs
B	It is the use of thermostat anticipation for the increase of energy conservation
C	It is the gradual return of space temperature to the system’s set point after a system setback
D	None of the above

Question 29

The override feature on a programmable thermostat

A	Is used to temporarily bypass the heating control circuit
B	Is used to temporarily bypass the cooling control circuit
C	Is commonly accomplished by using the override or hold button
D	All of the above

Question 30

What is the purpose of the limit control on a heating system?

A	It controls the blower motor
B	It limits the amount of gas that is brought to the heat exchanger
C	It energizes the gas valve when the thermostat calls for heat and monitors space temperature
D	It de energizes the gas valve if the temperature of the heat exchanger becomes excessive

Question 31

The limit switch that is used on a forced air gas fired furnace is commonly

A	A closed bimetal switch
B	An open bimetal switch
C	A closed pressure sensitive switch
D	An open pressure sensitive switch

Question 32

A limit switch that is used on a forced air gas fired furnace

A	Can only be an automatic type of a reset
B	Can only be manual type of a reset
C	Can be an automatic or a manual type of a reset
D	Must be replaced if the switch opens to the circuit

Question 33

What is the purpose of a low pressure switch when it is used in an air conditioning system?

A	It makes the circuit to the compressor if the low side pressure drops too low
B	It breaks the circuit to the compressor if the high side pressure drops too low
C	It makes the circuit to the compressor if the high side pressure drops too low
D	It breaks the circuit to the compressor if the low side pressure drops too low

Question 34

The low pressure switch will

A	Close on a rise in pressure and open on a drop in pressure
B	Open on a rise in pressure and close on a drop in pressure
C	Close if the system has lost its refrigerant charge
D	Open if the condenser has a loss of airflow

Question 35

What is the purpose of the high pressure switch when it is used in an air conditioning system?

A	It makes the circuit to the compressor if the low side pressure rises too high
B	. It breaks the circuit to the compressor if the high side pressure rises too high
C	. It makes the circuit to the compressor it the high side pressure rises too high
D	It breaks the circuit to the compressor if the low side pressure rises too high

Question 36

The high pressure switch will

A	Close on a rise in pressure and open on a drop in pressure
B	Open on a rise in pressure and close on a drop in pressure
C	Close if the system has an excessive refrigerant charge
D	Open if the air filter near the indoor coil becomes plugged

Question 37

A reverse acting high pressure switch is used to?

A	Energize the compressor when the pressure of the system is within operable limits
B	De energize the compressor when the system’s pressure becomes excessive
C	De energize the condenser fans on a decrease of ambient temperature
D	De energize the condenser fans on an increase of ambient temperature

Question 38

What is the purpose of a relay?

A	It converts a power source from a high voltage to a low voltage
B	It controls a higher voltage circuit by a signal from a lower voltage circuit
C	It can only be used to control motor circuits
D	It changes an AC power supply to a DC power supply

Question 39

The contacts of a relay must never exceed

A	5 amps
B	10 amps
C	20 amps
D	40 amps

Question 40

When measuring the resistance of a relay coil and an infinite resistance is found, what is the problem with the relay?

A	The relay is in operable condition
B	The relay coil is shorted
C	The relay coil has continuity
D	The relay coil is burnt open

Question 41

What must be taken into consideration when replacing a relay?

A	Replace the relay with the same coil voltage and switch contact configuration
B	Replace the relay with the same coil amperage, contact voltage rating, and switch contact configuration
C	Replace the relay with the same coil resistance, contact voltage rating, and mounting bracket
D	Replace the relay with a higher coil resistance, the same amperage rating, and always add contacts for added load demands

Question 42

What is the major difference between a relay and a contactor?

A	A relay coil voltage is 24 volts and a contactor can be 24 or 120 volts
B	A contactor has more resistance across its coil
C	A contactor contact rating is higher than that of a relay
D	A contactor can be used in motor circuits and a relay cannot

Question 43

When testing a contactor with an ohmmeter, a good operating contactor will read

A	Zero resistance across the coil
B	Measurable resistance across the coil
C	Infinite resistance across the coil
D	Measurable resistance across the contacts

Question 44

What is the major difference between a contactor and a starter?

A	A starter incorporates built in overload protectors and a contactor does not
B	A starter is used on loads that are 460 v, and a contactor is used on loads that are 220 v
C	The starter coil voltage ranges from 220 to 460 volts, and a contactor is 24 volts
D	The contacts of a contactor will change positions immediately after the coil is energized and the changing of the starter contacts are delayed

Question 45

When measuring the resistance of a starter coil, zero resistance is found. What is the problem with the starter?

A	The starter is in operable condition
B	The starter coil is shorted
C	The starter coil has no continuity
D	The starter coil is burnt open

Question 46

Which type of overload protector is not incorporated in a starter?

A	A bimetal relay
B	A thermal relay
C	A molten metal relay
D	A potential relay

Question 47

When a timed delay relay is used during the heating cycle, what part of the circuit does it commonly control?

A	The gas valve circuit
B	The thermostat circuit
C	The blower circuit
D	The accessories circuit

Question 48

Why would a timed delay relay circuit be used on an air conditioning system?

A	To prevent short cycling of the condenser fans
B	To prevent short cycling of the compressor
C	To prevent short cycling of the indoor blower
D	To delay the operation of the condenser fan until high side pressure is established

Question 49

What type of time delay is commonly used to de energize a blower on a forced air heating system?

A	A normally closed delay on make
B	A normally open delay on make
C	A normally closed delay on break
D	A normally open delay on break

Question 50

What is the purpose of a sequencer?

A	It reduces inrush current by sequentially energizing and de energizing loads in an HVAC system
B	It reduces holding current by sequentially energizing and de energizing loads in an HVAC system
C	It reduces inrush voltage by sequentially energizing and de energizing loads in an HVAC system
D	It reduces resistance by sequentially energizing and de energizing loads in an HVAC system

Question 51

Sequencers are commonly found on

A	Residential gas fired furnaces
B	Commercial rooftop air conditioning systems
C	Residential air conditioning systems
D	Electric heating systems

Question 52

What component is often used in an electrical circuit as a sequencer?

A	A defrost timer
B	A magnetic switching relay
C	A microprocessor
D	A contactor

Question 53

On what system is a defrost timer commonly found?

A	A heat pump system
B	A commercial air conditioning system
C	A residential air conditioning system
D	A cooling tower system

Question 54

What are two methods that are used to control a defrost cycle?

A	Defrost timers and switching relays
B	Defrost timers and timed delay relays
C	Defrost timers and sequencers
D	Defrost timers and micro-processsors

Question 55

What is the purpose of a solenoid valve?

A	It controls the flow of current through a circuit
B	It controls the flow of a fluid
C	It allows a technician to read pressures on a manifold gauge set
D	It controls the amount of refrigerant in an evaporator coil

Question 56

An automatic pump down system uses

A	A high pressure switch, a thermostat, and a solenoid valve in its circuit
B	A high pressure switch, a compound gauge, and a solenoid valve in its circuit
C	A low pressure switch, a solenoid valve, and a thermostat in its circuit
D	A thermostat, a solenoid valve, and a reversing relay in its circuit

Question 57

What component is commonly used to control refrigerant flow in a heat pump system?

A	A reversing valve solenoid
B	A hot gas solenoid
C	A liquid line solenoid
D	A bypass solenoid

Question 58

What component is used to protect the compressor during low outdoor ambient conditions?

A	A subcooler
B	A crankcase heater
C	A thermal electric expansion valve
D	A de-superheat coil

Question 59

What is the purpose of the crankcase heater?

A	To increase oil viscosity during low ambient conditions
B	To increase the efficiency of a system during low ambient conditions
C	To prevent refrigerant migration into the compressor during low ambient conditions
D	To decrease oil viscosity for proper lubrication of internal components

Question 60

What is the BTU output of an electric heater that is rated at 1,500 watts?

A	5,118 Btu
B	4,710 Btu
C	478 Btu
D	440 Btu

Question 61

What controls the electric heating elements in an air to air heat pump system?

A	The first stage of a two stage of a two stage thermostat
B	The second stage of a two stage thermostat
C	The reversing valve relay
D	The anticipator relay

Question 62

Where are auxiliary strip heaters commonly located on an air to air heat pump?

A	In the return air duct before the indoor blower
B	In the return air duct after the indoor blower
C	In the supply air plenum before the indoor coil
D	In the supply air plenum after the indoor coil

Question 63

What component is commonly used as a flame roll out sensor on a gas fired furnace?

A	A diode
B	A transistor
C	An electric heating element
D	A fusible link

Question 64

How is a fusible link wired when it is in an electric heating system?

A	In parallel with the heating element
B	In series with the heating element
C	In parallel with the heating element relay coil
D	In series with the heating element relay coil

Question 65

A step down transformer is designed to

A	Take a lower amperage and increase it to a higher amperage
B	Take a higher amperage and decrease it to a lower amperage
C	Take a lower voltage and increase it to a higher voltage
D	Take a higher voltage and decrease it to a lower voltage

Question 66

On a step up transformer, the turn ratio from the primary side to the secondary side will be

A	Higher on the primary than on the secondary
B	Lower on the primary than on the secondary
C	The same on the primary as on the secondary
D	The same as a step down transformer

Question 67

If a transformer uses a 240 v primary winding that has 400 turns and a secondary that has 200 turns, what would be the voltage of the secondary winding?

A	200 v
B	120 v
C	480 v
D	None of the above

Question 68

When replacing a 24 volt control transformer that has the VA rating of 40, what is the maximum amperage of the control circuit?

A	06 amp
B	.6 amp
C	1.6 amp
D	9.6 amp

Question 69

When there is voltage at the primary side of a transformer and no voltage at the secondary, what could the problem with the transformer?

A	A bad secondary winding only
B	A bad primary winding only
C	A bad secondary or primary winding
D	A bad fuse at the power supply

Question 70

When measuring an open secondary winding of a transformer, what measurement will be obtained?

A	An infinite resistance
B	A measurable resistance
C	A zero resistance
D	continuity

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Electrical Controls

Electrical Controls

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