HVAC Review

Question 1

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

Answer 1

Second stage heating

Question 2

What is the ‘R’ terminal?

Answer 2

24V supply

Question 3

What Is the ‘W’ terminal for?

Answer 3

Heat

Question 4

What is the ‘G’ terminal for?

Answer 4

The fan

Question 5

What is the ‘Y’ terminal for?

Answer 5

Cooling

Question 6

What is the ‘C’ terminal for?

Answer 6

Common

Question 7

Heating systems are rated according the amount of what?

Answer 7

Energy input into the system

Question 8

True or false

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

Answer 8

True

Question 9

Convection is heat transfer in which form?

Answer 9

Through air

Question 10

Four reasons for automatic control

Answer 10

Comfort, economy, convenience, safety

Cecs

Question 11

What is a closed loop system?

Answer 11

A system that uses feedback to make a process automatic

Question 12

What is high limit control generally set at?

Answer 12

80 - 100 degrees celsius

Question 13

What are the typical fan settings

Answer 13

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

Question 14

List three types of contacts used in thermostats

Answer 14

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

Question 15

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

Answer 15

In series

Question 16

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

Answer 16

In parallel

Question 17

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

Answer 17

In parallel with he fan control switch

Question 18

What is a common name for a manual override switch?

Answer 18

Summer switch

Question 19

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

Answer 19

Spiral type
Strip type
Disc type

Question 20

What is the open circuit voltage of a thermocouple?

Answer 20

26-32 mVdc

Question 21

What is the closed circuit voltage of a thermocouple?

Answer 21

7.5-15 mVdc

Question 22

What does hrv stand for?

Answer 22

Heat recovery ventilator

Question 23

High efficiency furnaces are also know as what?

Answer 23

Condensing furnaces

Question 24

What does afue stand for?

Answer 24

Annual fuel utilization fee

Question 25

What is the afue of a mid efficiency furnace?

Answer 25

80 -90%

Question 26

Gat device proves the operation of the cab?

Answer 26

The air prove controller

Question 27

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

Answer 27

Hot Surface ignition Direct Spark Intermittent pilot

Question 28

True or false | The combustion air prove controller is a normally open pressure switch

Answer 28

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

Question 29

List four types of humidifiers that can be installed on furnaces

Answer 29

Standing water absorbent Rotating drum Rotating disk Flow through

Question 30

Another term for hot water heat is?

Answer 30

Hydronic heat

Question 31

List some Common terminal heat exchange units

Answer 31

Radiators, unit heaters, radiant panels

Question 32

What is the maximum capacity for a class 2 transformer

Answer 32

100 va

Question 33

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

Answer 33

Direct spark ignition Hot surface ignition Standing pilot flame

Question 34

List the five main components of a cooling system

Answer 34

``` Condenser coil Evaporator coil Refrigerant Compressor Refrigerant control valve (TX valve) ```

Question 35

What is the purpose of the evapourator

Answer 35

Absorbs heat from the air blowing through its fins

Question 36

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

Answer 36

To cool the compressed hot refrigerant vapour

Question 37

List 3 types of rcv's

Answer 37

Thermostatic expansion valve Thermal electric valve Automatic expansion valve

Question 38

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

Answer 38

Evapourator 2 speed blower Compressor and condenser

Question 39

List 3 major sections of an HVAC system

Answer 39

Heating Cooling Ventilation

Question 40

True or false | A flame proving circuit has an approximate circuit current value of 1.5 to 4 micro amps

Answer 40

True

Question 41

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

Answer 41

True

Question 42

True or false | The location of air conditioning equipment a disconnect means within site and 1m from equipment

Answer 42

False Within 3 28-604

Question 43

A direct fired MUAU has how many heat exchangers?

Answer 43

None motha fucka

Question 44

List 3 reasons for heat trace

Answer 44

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

Question 45

List the four main types of heat tracing systems

Answer 45

Self regulating variable resisting Series fixed Parallel fixed Skin effect

Question 46

What is an AHU?

Answer 46

Air handling unit

Question 47

What is an RTU?

Answer 47

Roof top unit

Question 48

What is an MUA?

Answer 48

Make up air unit | 1 unit that replaces exhausted air

Question 49

What is a VAV?

Answer 49

Variable air volume box

Question 50

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

Answer 50

False | It is normally closed