[D2L] Final Review

Question 1

What is the Branch pressure of a 2 pipe Thermostat

Answer 1

0-20psi

Question 2

What control system has ultimate authority over all building functions?

Answer 2

Fire Alarm

Question 3

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

Answer 3

False, it operates indirectly to protect the motor

Question 4

Two Position Thermostats are analog

Answer 4

False, they are digital

Question 5

How do low pressure controllers usually operate?

Answer 5

Close on Rise/Open on Fall

Question 6

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

Answer 6

the adjusted value subtracts from the set point

Question 7

How many conductors in a CAT 5 cable

Answer 7

8

Question 8

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

Answer 8

Greater capacity and ability to control multiple actuators

Question 9

An actuator controls the dampers in an HVAC unit

Answer 9

True

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

What type of control system are relays and contactors considered?

Answer 12

electromechanical

Question 13

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

Answer 13

resistance change polymer
gold foil grid
thin-film polymer

Question 14

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

Answer 14

Gas valve

Question 15

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

Answer 15

Deviation

Question 16

Solenoid valves are multi-directional

Answer 16

False, it’s digital so just on/off

Question 17

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

Answer 17

True

Question 18

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

Answer 18

put a screw driver inside it

Question 19

Mixed air controllers are typically set to what temperature?

Answer 19

50F - 60F

Question 20

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

Answer 20

Compressor

Question 21

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

Answer 21

Prevent oil foaming on compressor startup

Question 22

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

Answer 22

50F – 60F

Question 23

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

Answer 23

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

Question 24

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

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

Answer 24

Thermostat
Pressure Controller

Question 25

What type of control is a cooling thermostat considered?

Answer 25

Direct acting

Question 26

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

Answer 26

True

Question 27

What are the two air flows that are being mixed by an Economizer? 1) Return 2) Supply 3) Mixed 4) Outdoor

Answer 27

Return Outdoor

Question 28

Why do low temp refrigeration have oil return issues?

Answer 28

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

Question 29

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

Answer 29

Short Cycling

Question 30

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

Answer 30

True

Question 31

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

Answer 31

Pressure to rise throughout the system and close the pressure control

Question 32

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

Answer 32

G,R,Y

Question 33

What is the difference between a relay and a contactors?

Answer 33

Relays are under 15 Amps Contactors are over 15 Amps

Question 34

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

Answer 34

True

Question 35

What are the 3 common types of sensors? 1) humidity 2) flow 3) pressure 4) temp 5) level

Answer 35

humidity pressure temp

Question 36

A system without controller feedback is called an open loop

Answer 36

True

Question 37

Range is the Min and Max Setting of a controller

Answer 37

True

Question 38

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

Answer 38

(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

Question 39

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

Answer 39

8.80 vdc

Question 40

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

Answer 40

7.20 maDC

Question 41

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

Answer 41

75%

Question 42

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

Answer 42

69%