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HVAC > Principles Of Automatic Heating And Cooling Controls > Flashcards

Principles Of Automatic Heating And Cooling Controls Flashcards

1
Q

What is meant by the term cold?

A

Cold is the relative lack of heat

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2
Q

What is the approximate definition of BTU?

A

British Thermal Unit

- The amount of heat required to raise the temperature of 1 pound of water by 1 degree F.

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3
Q

Heat transfer in an object is always from hot to cold.

True or False?

A

True

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4
Q

Convection is the way heat is transferred by…

A

Fluids

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5
Q

Referring to heating/cooling systems, list 4 factors that affect human comfort.

A

Temperature
Humidity
Air movement
Radiation

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6
Q

In a closed loop system, feedback is optional.

True or False?

A

False.

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7
Q

A device that reacts to changes in a variable condition is referred to as:

  1. a relay device
  2. a controlling device
  3. an igniting device
  4. a load device
A

Controlling device

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8
Q

A limit or safety device detects dangerous conditions in the system.

True or False?

A

True

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9
Q

A control circuit for a residential heating system is an example of a closed loop control system.

True or False?

A

True

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10
Q

The heat exchanger:

  1. contains the heated air that is distributed by the ducts
  2. is a mechanical device that opens to allow heated air into a room
  3. is an electrical device that opens a damper to allow heated air into a room
  4. is a steel enclosure that transfers heat to the air distributed by the ducts
A
  1. is a steel enclosure that transfers heat to the air distributed by the ducts
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11
Q

In a domestic gas furnace the fan motor starts when:

  1. the room thermostat contacts close to call for heat
  2. the main burner gas valve opens
  3. the air in the plenum warms up to a preset temperature
  4. the thermocouple produces sufficient voltage to pull in the relay
A
  1. the air in the plenum warms up to a preset temperature
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12
Q

If the plenum gets to hot the high limit device will shut off the fan motor.

True of False?

A

False

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13
Q

In a properly operating domestic gas furnace the fan motor could keep running after the main burner shuts off.

True of False?

A

True

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14
Q

A schematic diagram is used to show

  1. the location of components
  2. the relative size of components
  3. the logical operation of components
  4. the electrical rating of components
A
  1. the logical operation of components
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15
Q

If you wanted to find out the relative position of components in a heating system and the wiring between them, you would look at

A

A wiring diagram

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16
Q

A schematic diagram is drawn with

  1. Power on and at 20 degrees C
  2. Power off and no heat
  3. Power on and no heat
  4. Power of and at 20 degrees C
A
  1. Power off and no heat
17
Q

An example of a load device is

  1. A thermostat
  2. An N.O. contact
  3. A high limit switch
  4. A relay coil
A
  1. A relay coil
18
Q

An example of a controlling device is

  1. a heater
  2. a pressure switch
  3. a motor
  4. Both 1 and 3
A
  1. a pressure switch
19
Q

A gas fired furnace in a single dwelling always needs a properly labeled disconnect switch near the furnace

True or False?

A

False

Rule 26-806

20
Q

A residential furnace is allowed to have the light in the furnace room on its supply circuit.

True or False?

A

False

Rule 26-806

21
Q

The 24V Class 2 control wiring to the thermostat for residential gas fire heating systems can utilize LVT cable.

True or False?

A

True

Rule 16-210
Table 19

22
Q

In a forced air furnace the sensing element for the fan is mounted in the heat exchanger.

True or False?

A

False

23
Q

People may feel cold even if the temperature is 20 degrees C

a) False
b) True, if the humidity is to high
c) true if the humidity is to low
d) true if there is insufficient air movement over the body

A

c) true if the humidity is to low

24
Q

When control devices in a domestic heating system are connected such that any “1” device could deactivate the main gas valve the devices would be connected in

Series or Parallel?

A

Series

25
Q

A forced air system relies on gravity to circulate the warm air.

True or False?

A

False

26
Q

Two control devices are connected in series to control one load device. One control device is closed and the other is open.
The load device will be:

a) On
b) Off
c) On or Off depending on something
d) Not working properly

A

b) Off

27
Q

A human body can lose heat by radiation if it is to close to a cold wall.

True or False?

A

True

28
Q

Low relative humidity can make a room feel colder than it actually is.

True or False?

A

True

29
Q

In a forced air gas furnace, the smoke and exhaust gasses are found:

a) inside the heat exchanger
b) in the plenum
c) at the registers
d) in the duct

A

a) inside the heat exchanger

30
Q

If the temperature becomes dangerously high in a domestic forced air furnace, which device should safely shut down the heating equipment.

a) the high limit
b) the fan limit
c) auxiliary contact
d) thermocouple

A

a) the high limit

31
Q

Rules pertaining to the installation of HVAC systems and equipment are grouped into one section of the code book?

True or False?

A

False

32
Q

Convection is a method by which heat is transferred through solids.

True or False?

A

False

33
Q

Thermostatically controlled heating systems are considered _______ loop systems

A

Closed

34
Q

A heating thermostat symbol on a schematic should be shown

a) N.C. and opens on a rise of temperature
b) N.O. and closed on a drop in temperature
c) N.O. and closes on a rise in temperature
d) None of the above

A

a) N.C. and opens on a rise of temperature

35
Q

Controlling devices react to changes in variable conditions such as temperature, pressure or humidity.

True or False?

A

True

36
Q

What is meant by the term heat?

A

Heat is energy in transfer

HVAC (9 decks)

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