HVAC

Question 1

Thermostat mounted above floor height?

Answer 1

1.3m- 1.5m

Question 2

3 types of thermostats

Answer 2

Lien voltage
Low voltage
Electronic

Question 3

Line voltage thermostat explain

Answer 3

Acts as on/off switch to heater SPST OR DPST

CAN ONLY HAVE OFF SETTING IF ALL UNGROUNDED CONDUCTORS OPEN IN CCT WHEN OFF

Question 4

Low voltage thermostat advantage

Answer 4

Stepped down for safety purpose less voltage

Cheaper wiring small wire size required

Question 5

What is max breaker size for heating cct in residential base board heating

Answer 5

30amp

Question 6

Unit heaters explain

Answer 6

Heater and blower fan - can be mounted on ceiling or on wall. Not allowed to be faced towards surface that could reach 90c heat

Question 7

Electric furnace explain

Answer 7

Blower heater forces air through duct work in floor.

Mounted vertical or horizontal on floor or on walls

Question 8

Gas furnace explain

Answer 8

Same principle as electric furnace. Blows air through ducts in floor.

Usually in basement of house
Use thermopile to provide small voltage to keep pilot light lit

Question 9

What prevents combustible gases from circulating around house

Answer 9

Heat exchanger (used on gas furnace)

Question 10

Heating cable set explain

Answer 10

Underfloor heat / concrete heat trace etc.

150-300mm spacing for floor heat
DO NOT SHORTEN CABLE - fire danger as decreases resistance and heats up to unsafe temperature

Question 11

Geothermal systems explain

Answer 11

Take air from 7m underground to heat.

Open loop= draws water from well or hot spring

Closed loop = circulated filtered water

Question 12

What does damper do

Answer 12

Regulated air flow

Question 13

Types of fans

Answer 13

Centrifugal and axial

Question 14

Types of axial fans

Answer 14

Propeller
Tube-axial
Vaneaxial

Question 15

Valves definition

Answer 15

Regulate flow of water through coils

Question 16

Gas cannot flow without pilot flame- how to make this safety

Answer 16

Thermopile provides small voltage to keep open gas valve when heated by the flame. If flame goes out thermopile cannot create voltage and contact will
Close to gas valve killing the gas intake

Question 17

Electrical air cleaners

Answer 17

Used electrostatic to remove dust/pollen

DANGER FROM ELECTRIC SHOCK - must be interlocked with blower

DANGER - OZONE ACCUMLATION

Question 18

Electric duct heaters

Answer 18

Used with central blower fan to serve two or more zones in building. Used in large commercial and industrial.

Question 19

Plenum heaters explain

Answer 19

Electric heater used to reduce oil consumption and cheaper energy bills

Question 20

Domestic water heaters explain

Answer 20

Electric boilers hydronic system- uses water to pump through radiators around house. Uses natural convection to heat

Question 21

5 components

Answer 21

Evaporator
Expansion valve
Compressor
Condenser
Refrigerant

Question 22

Dx meaning

Answer 22

Direct expansion

Question 23

How does hvac work

Answer 23

Uses evaporation and condensation of refrigerant.

Question 24

Heat pump switch from cool to heat

Answer 24

Switch the condenser and the evaporator around

Question 25

What class is hvac controls

Answer 25

Class 2 Class 1= threat of fire and death

Question 26

Advantages of computer based controls

Answer 26

Precise control Reliable Flexibility

Question 27

Evaporator job

Answer 27

Absorbs heat from the air in a room/space

Question 28

Compressors job

Answer 28

Increase the pressure of refrigerant and transfer to condenser

Question 29

Expansion valve job

Answer 29

Removes pressure from liquid refrigerant to allow change in state from liquid to Vapor

Question 30

Condensers job

Answer 30

Release heat that has been absorbed by the room out the outdoors