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HVAC > HVAC Review > Flashcards

HVAC Review Flashcards

1
Q

The terminal labeled ‘W2’ on a seven-wire thermostat is used to connect to what?

A

Second stage heating

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2
Q

What is the ‘R’ terminal?

A

24V supply

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3
Q

What Is the ‘W’ terminal for?

A

Heat

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4
Q

What is the ‘G’ terminal for?

A

The fan

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5
Q

What is the ‘Y’ terminal for?

A

Cooling

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6
Q

What is the ‘C’ terminal for?

A

Common

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7
Q

Heating systems are rated according the amount of what?

A

Energy input into the system

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8
Q

True or false

A t stat is a controlling device that provides feedback to a load device

A

True

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9
Q

Convection is heat transfer in which form?

A

Through air

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10
Q

Four reasons for automatic control

A

Comfort, economy, convenience, safety

Cecs

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11
Q

What is a closed loop system?

A

A system that uses feedback to make a process automatic

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12
Q

What is high limit control generally set at?

A

80 - 100 degrees celsius

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13
Q

What are the typical fan settings

A

Fan on 49 - 60
Fan off 32 -38
Differential 17-22

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14
Q

List three types of contacts used in thermostats

A

Mercury ( most popular)
Spring activated or snap action exposed
Glass enclosed magnet and armature snap acting

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15
Q

How is the anticipator connected with the thermostat in a heating system?

A

In series

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16
Q

How is the anticipator connected with the thermostat in a cooling system?

A

In parallel

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17
Q

Where would a manual override switch be installed in a heating system?

A

In parallel with he fan control switch

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18
Q

What is a common name for a manual override switch?

A

Summer switch

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19
Q

What are the 3 main types of bi metallic temp sensing devices?

A

Spiral type
Strip type
Disc type

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20
Q

What is the open circuit voltage of a thermocouple?

A

26-32 mVdc

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21
Q

What is the closed circuit voltage of a thermocouple?

A

7.5-15 mVdc

22
Q

What does hrv stand for?

A

Heat recovery ventilator

23
Q

High efficiency furnaces are also know as what?

A

Condensing furnaces

24
Q

What does afue stand for?

A

Annual fuel utilization fee

25
Q

What is the afue of a mid efficiency furnace?

A

80 -90%

26
Q

Gat device proves the operation of the cab?

A

The air prove controller

27
Q

List the 3 types of electronic ignition systems may be used with efficient furnaces

A

Hot Surface ignition
Direct Spark
Intermittent pilot

28
Q

True or false

The combustion air prove controller is a normally open pressure switch

A

False
Normally closed
Acts on a negative air pressure ( suction pulls it in to close contacts)

29
Q

List four types of humidifiers that can be installed on furnaces

A

Standing water absorbent
Rotating drum
Rotating disk
Flow through

30
Q

Another term for hot water heat is?

A

Hydronic heat

31
Q

List some Common terminal heat exchange units

A

Radiators, unit heaters, radiant panels

32
Q

What is the maximum capacity for a class 2 transformer

A

100 va

33
Q

List the 3 types of ignition devices that may be used for hot water heating systems

A

Direct spark ignition
Hot surface ignition
Standing pilot flame

34
Q

List the five main components of a cooling system

A 
Condenser coil 
Evaporator coil
Refrigerant
Compressor
Refrigerant control valve (TX valve)
35
Q

What is the purpose of the evapourator

A

Absorbs heat from the air blowing through its fins

36
Q

What is the purpose of the condenser in a cooling system?

A

To cool the compressed hot refrigerant vapour

37
Q

List 3 types of rcv’s

A

Thermostatic expansion valve

Thermal electric valve

Automatic expansion valve

38
Q

Adding a cooling system to an existing residential furnace requires the addition of what 3 mechanical components?

A

Evapourator
2 speed blower
Compressor and condenser

39
Q

List 3 major sections of an HVAC system

A

Heating
Cooling
Ventilation

40
Q

True or false

A flame proving circuit has an approximate circuit current value of 1.5 to 4 micro amps

A

True

41
Q

In a cooling system a high pressure sensor is connected to the discharge side of the compressor. This high pressure sensor is a normally open pressure switch

A

True

42
Q

True or false

The location of air conditioning equipment a disconnect means within site and 1m from equipment

A

False
Within 3
28-604

43
Q

A direct fired MUAU has how many heat exchangers?

A

None motha fucka

44
Q

List 3 reasons for heat trace

A

To melt ice and snow
Keep pipes and valves from freezing
Keep liquids inside of pipes at a maintained temp

45
Q

List the four main types of heat tracing systems

A

Self regulating variable resisting
Series fixed
Parallel fixed
Skin effect

46
Q

What is an AHU?

A

Air handling unit

47
Q

What is an RTU?

A

Roof top unit

48
Q

What is an MUA?

A

Make up air unit

1 unit that replaces exhausted air

49
Q

What is a VAV?

A

Variable air volume box

50
Q

In a cooling system, the high pressure sensor is a normally open pressure switch.
True or false

A

False

It is normally closed

HVAC (3 decks)

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