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Controls [FINALIZED!] > [D2L] Final Review > Flashcards

[D2L] Final Review Flashcards

1
Q

What is the Branch pressure of a 2 pipe Thermostat

A

0-20psi

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2
Q

What control system has ultimate authority over all building functions?

A

Fire Alarm

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3
Q

A pilot duty overload interrupts the current to the motor directly?

A

False, it operates indirectly to protect the motor

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4
Q

Two Position Thermostats are analog

A

False, they are digital

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5
Q

How do low pressure controllers usually operate?

A

Close on Rise/Open on Fall

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6
Q

On a CONSTANT CUT IN, the thermostat is adjusted by the dial on the front. what does the adjusted number change?

A

the adjusted value subtracts from the set point

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7
Q

How many conductors in a CAT 5 cable

A

8

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8
Q

Advantage of 3 pipe controller over a 2 pipe controller is….

A

Greater capacity and ability to control multiple actuators

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9
Q

An actuator controls the dampers in an HVAC unit

A

True

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10
Q

Select all positions that works floating point control (Hint: There are 3 commands) (MULTI-SELECT)

1) switch 1 - ON ; switch 2 - OFF
2) switch 1 - OFF ; switch 2 - OFF
3) switch 1 - OFF ; switch 2 - ON
4) switch 1 - ON ; switch 2 - ON

A

1) switch 1 - ON ; switch 2 - OFF
2) switch 1 - OFF ; switch 2 - OFF
3) switch 1 - OFF ; switch 2 - ON

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11
Q

What is the difference between a line duty and pilot duty overload device?

A

Pilot duty interrupts the control current and line duty interrupts the line current

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12
Q

What type of control system are relays and contactors considered?

A

electromechanical

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13
Q

What is an electronic hygroscopic sensor made of? (MULTISELECT 3)

1) nylon ribbon
2) resistance change polymer
3) golf foil grid
4) human hair
5) thin-film polymer

A

resistance change polymer
gold foil grid
thin-film polymer

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14
Q

When the High limit trips on a furnace, it kills power to what?

A

Gas valve

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15
Q

In an electronic thermostat, the length of time it takes for the control point and the setpoint to equalize is called:

A

Deviation

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16
Q

Solenoid valves are multi-directional

A

False, it’s digital so just on/off

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17
Q

Only semi-hermetic compressors that have oil pumps, use an oil failure control

A

True

18
Q

How can you prevent damage to a solenoid coil if it is energized off its valve stem?

A

put a screw driver inside it

19
Q

Mixed air controllers are typically set to what temperature?

A

50F - 60F

20
Q

What do OFC’s protect in a system from insufficient lubrication?

A

Compressor

21
Q

Why is the crankcase heater energized for the compressor during the shut down period?

A

Prevent oil foaming on compressor startup

22
Q

What is an acceptable temperature dry bulb setpoint for a change-over thermostat?

A

50F – 60F

23
Q

In a freezer, the Fan Delay’s job is to…

A

Allow water to freeze on it after a defrost prior to the fans starting up

24
Q

Pick the two devices that are required for a pump-down control system (multiselect)

1) Thermostat
2) Contactor
3) Flow Controller
4) Pressure Controller

A

Thermostat
Pressure Controller

25
Q

What type of control is a cooling thermostat considered?

A

Direct acting

26
Q

A semiconductor relay has no moving parts, inexpensive, switch more quickly and have a longer life expectancy

A

True

27
Q

What are the two air flows that are being mixed by an Economizer?

1) Return
2) Supply
3) Mixed
4) Outdoor

A

Return
Outdoor

28
Q

Why do low temp refrigeration have oil return issues?

A

low density refrigerant suction vapour doesn’t carry oil with it as well

29
Q

What is a delay on break control best suited to monitor?

A

Short Cycling

30
Q

The condenser fan controller cycles the condenser fans in response to a discharge pressure, ambient temperature or liquid line temperature and thus maintains a minimum discharge pressure

T or F

A

True

31
Q

When a pump down control system thermostat first calls it sends power to the LLS solenoid allowing the refrigerant to do what?

A

Pressure to rise throughout the system and close the pressure control

32
Q

On a call for cooling what terminals will have 24V present?

A

G,R,Y

33
Q

What is the difference between a relay and a contactors?

A

Relays are under 15 Amps
Contactors are over 15 Amps

34
Q

For the Oil Failure Controller to operate correctly…

The crankcase pressure needs to be lower than the oil pump pressure to verify pressure difference

T or F

A

True

35
Q

What are the 3 common types of sensors?

1) humidity
2) flow
3) pressure
4) temp
5) level

A

humidity
pressure
temp

36
Q

A system without controller feedback is called an open loop

A

True

37
Q

Range is the Min and Max Setting of a controller

A

True

38
Q

What is the sequence of operation for a heating cycle in the carrier furnace from the residential heating videos?

A

(1) Thermostat R closes to W
(2) Inducer runs
(3) Pressure switches close
(4) HSI is energized
(5) Gas valve energized
(6) Flame signal is proven by the flame sensor
(7) Blower turns on after a determined time
(8) When the thermostat is satisfied, terminals R to W opens, inducer motor runs for additional 15 seconds, gas valve is de-energized and blower continues to run for an additional 90 seconds

39
Q

determine the expected feedback signal from a 2-10vdc control in response to a 85 % demand

A

8.80 vdc

40
Q

determine the control signal you would expect from a 20 % demand in a 4-20maDC control system

A

7.20 maDC

41
Q

what is the demand on an analog control receiving a 8vdc from a 2-10vdc control system

A

75%

42
Q

what is the demand on an analog control receiving a 15maDC from a 4-20madc control system

A

69%

Controls [FINALIZED!] (19 decks)

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