Deck 14: Automatic Control Components and Applications

Question 1

A helix coil is used in some applications to sense temperature in a moving air stream.

Answer 1

True

Question 2

A low pressure control has a "high event" and a "differential" setting. The technician wants the system to turn on at 28 psig and shut down at 2 psig. What would be the proper settings?

A) High event: 28 psig, differential: 2 psig.
B) High event: 2 psig, differential: 2 psig.
C) High event: 28 psig, differential: 26 psig.
D) High event: 2 psig, differential: 28 psig.

Answer 2

C

Question 3

The difference between system overshoot and system lag is called ____.

A) room temperature
B) temperature rise
C) temperature swing
D) room swing

Answer 3

C

Question 4

The heater in the thermostat control circuit in the cooling mode is active when the ____.

A) cooling contact is open
B) cooling contact is closed
C) fan switch is open
D) fan switch is closed

Question 5

To prove that the combustion blower motor is operating before ignition, a ____ would be used.

A) toggle switch
B) pressure differential switch
C) push button switch
D) sail switch

Question 6

The purpose of a heat anticipator is to ____.

A) anticipate a sudden rise in temperature
B) keep the thermostat warm
C) reduce the temperature swing of a conditioned space
D) ensure that the system transformer does not overheat

Question 7

If the suction pressure of a system is 60 psig and the oil pump outlet is 85 psig, what is the net oil pressure?

A) 60 psig
B) 25 psig
C) 85 psig
D) 145 psig

Question 8

To obtain an accurate reading of a fluid in a large pipe, a technician should ____.

A) strap a dial-type pocket thermometer to the pipe
B) use a digital thermometer in a glass of ice water
C) use a permanently mounted thermometer in a well
D) Any of the above will work fine.

Question 9

Where would a water regulating valve that is controlling head pressure be installed?

A) Water circuit at inlet of condenser.
B) Discharge line at outlet of compressor.
C) Suction line.
D) Liquid line close to the condenser.

Question 10

Oil pressure safety controls measure the difference in pressure to establish ____.

A) the compressor is running
B) the oil pump is running
C) that negative oil pressure is present
D) that positive oil pressure is present

Question 11

The cold anticipator is wired in ____ with the mercury bulb cooling contacts and is energized during the off cycle.

A) parallel
B) series
C) sequence
D) opposition

Question 12

To properly set the heat anticipator, the ____  must determine what the current flow is through the heating control circuit when the furnace is operating in a steady state condition .

A) manufacturer
B) homeowner
C) electrician
D) heating technician

Question 13

The cold anticipator starts the cooling system early to allow the air-conditioning system to get up to capacity when needed.

Question 14

To control ice build-up on a heat pump outdoor coil in the heating cycle, a ____ is attached to a large diaphragm.

A) toggle switch
B) micro-switch
C) push button switch
D) sail switch

Question 15

The heat anticipator in the thermostat control circuit in the heating mode is active when the ____.

A) heating contact is open
B) heating contact is closed
C) fan switch is open
D) fan switch is closed

Question 16

The heat anticipator in a thermostat prevents the temperature in the conditioned space from rising above the thermostat setting.

Question 17

When a water regulating valve is used to control the head pressure of a water-cooled system, the valve's spring is acting against which pressure to modulate the water flow?

A) Head pressure of the system.
B) Water pressure.
C) Suction pressure.
D) Atmospheric pressure.

Question 18

Line voltage thermostats have heavier contacts and use which type of sensing element?

A) Bimetal.
B) Bellows.
C) Remote bulb.
D) All of the above.

Question 19

What is meant by the term "detent"?

A) Slow motion of a contact to ensure good electrical contact.
B) Rapid making and breaking of a contact.
C) The compensation furnished by heaters in the thermostat.
D) The control of the blower in the air handler.

Question 20

The advantage of using a thermistor-type thermometer over a mercury-filled thermometer for measuring refrigerant line temperature is that the thermistor-type does not have to be insulated.

Question 21

The term used to describe when the temperature of a heated room rises above the thermostat's set point is ____________________.

Question 22

What type of control would be used to cycle compressors on and off in response to evaporator pressures that indirectly control box temperatures?

Question 23

The term used to describe when the temperature of a heated room falls below the thermostat's set point is called ____________________.

Question 24

Explain the most accurate way to measure the current through the heat anticipator.

Question 25

Explain why the thermistor type sensor is normally embedded in the motor windings.

Question 26

Many natural gas fired heating units operate at a manifold pressure of 3.5 in. WC .

Question 27

High pressure control contacts are normally ____________________ type.

Question 28

Where is the thermistor motor overload device usually positioned?

Question 29

An oil pressure safety control usually has a 90-second time delay built into it. Why?

Question 30

A dual pressure control is actually a low pressure control and a high pressure control connected in parallel with each other.

Question 31

List four reasons why low voltage controls are usually found on residential air conditioning systems?

Question 32

The heater that functions in a thermostat in the cooling mode is called the ____________________.

Question 33

What device may be used to ensure that air is flowing through a duct before an electric strip heater is energized?

Question 34

The heater that functions in a thermostat in the heating mode is called the ____________________.