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Home Inspection > AC/Cooling > Flashcards

AC/Cooling Flashcards

1
Q

Two main parts of air conditioning units and locations of them

A
  1. Evaporator. In ductwork above furnace or in a fan coil in the attic
  2. Condenser. outdoors.
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2
Q

What is refrigerant?

A

A liquid/gas that moves heat

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3
Q

Refrigerant enters evaporator as a

A

Cold liquid 75%
Gas 25%

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4
Q

Refrigerant enters evaporator as a cold liquid. It removes heat from the house air which is blown across

A

The Cooling coil by a fan

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5
Q

As house air cools, water in the house

A

Condenses, reducing humidity

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6
Q

Compressor does what

A

Squeezes gas (high-pressure) raising temperature above outdoor temperatures

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7
Q

What enters condenser coil?

A

Hot gas

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8
Q

After hot gas enters condenser coil, what happens

A

The fan blows outdoor air across the coil, removing heat from the gas

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9
Q

As it cools, what happens to refrigerant

A

Condenses into a liquid

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10
Q

Does liquid or gas move indoors for AC

A

Liquid 75%
Gas 25%

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11
Q

liquid moves indoors and goes through a

A

Pressure reducing device

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12
Q

Liquid moves indoors and go through pressure reducing device, which does what

A

Cools the liquid below temperature of House air

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13
Q

Liquid passing through evaporator coil does what

A

It is evaporated into a gas again, removing more heat and humidity from house

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14
Q

Step-by-step process of A/C from compressor

A

Compressor
Hot gas
Fan
Liquid high temperature, high-pressure
Expansion device
Liquid low temperature low pressure
Evaporator coil in Plenum
Gas, low temperature, low pressure
Suction line
Back to compressor

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15
Q

Describe a compressor

A

Pump that moves refrigerant when it is a gas, raising its temperature

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16
Q

What is the heart of an A/C system and where is it located?

A

Compressor. Outdoors in condenser cabinet.

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17
Q

older and newer compressor types

A

Older= piston type
Newer = scroll type

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18
Q

Do not operate AC compressors below these temperatures

A

65°F or 16°C

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19
Q

Some compressors have these that must be on 12 to 24 hours prior to compressor starting up

A

Crank case heaters

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20
Q

What do crank case heaters do?

A

Make sure there is no liquid refrigerant mixed with lubricating oil

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21
Q

Compressor life, expectancies for moderate and hot climates

A

Moderate 10 to 15 years
Hot 8 to 10 years

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22
Q

These are 30 to 50% of the cost of an entire system

A

Compressors

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23
Q

Compressor should be level within how many degrees

A

10

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24
Q

What should be next to a compressor unit?

A

Disconnect for servicing

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25
Q

Where does an evaporator coil sit?

A

In ductwork, downstream of heat exchanger, or in an attic in a fan coil unit

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26
Q

Evaporator coil does what

A

Moves heat from house to refrigerant in the coil

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27
Q

What does condenser coil do

A

Removes heat from refrigerant to outside air

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28
Q

Describe the AC coils

A

Copper or aluminum tubing with thin fins to enhance heat transfer
(Fins are delicate and can be damaged by power washers )

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29
Q

What might be the cause of coils getting iced up

A

If airflow is restricted by a dirty air filter, air might not move quickly enough across the coils and cause ice up

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30
Q

Where should condenser units not be located?

A

Under decks or surrounded by shrubs (restricted airflow)

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31
Q

Where should condenser units not be

A

Near exhaust vents

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32
Q

What is required if a coil is in an attic?

A

An extra condensate pan (“attic drip pan”)

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33
Q

Condensate is ideally discharged directly outside. If discharging into a plumbing stack, what is required

A

A trap

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34
Q

Why should primary and auxiliary condensate lines not “Y” together?

A

Both could be affected by blockage

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35
Q

Why should drip pans have their own drain line?

A

Common drain lines between condensate tray and drip pan, may cause a flood if it plugs

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36
Q

What might the consequence be of the drain discharging into a plumbing stack?

A

It may allow sewer gases to back up into the house through the AC system

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37
Q

Describe the function of fans

A

Move air across coils, picking up or giving off heat

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38
Q

Should condenser fans be covered in the winter

A

Yes

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39
Q

Indoor fans are often furnace fans modified for increased airflow. Why?

A

Colder air is harder to push across evaporator coil, so to speed fans are used. (higher speed in the summer.)

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40
Q

How many CFM’s for AC air movement

A

400 to 450 CFM’s

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41
Q

What does CFM stand for?

A

Cubic feet per minute

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42
Q

Which are the small and large refrigerant lines for

A

Large= gas
Small = liquid

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43
Q

Which refrigerant lines are insulated and why?

A

Larger gas, refrigerant line to prevent condensation, and increase efficiency

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44
Q

What is the return line called?

A

Suction line

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45
Q

Is the suction line bigger or smaller?

A

Bigger

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46
Q

Does the suction line have gas or liquid?

A

Gas

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47
Q

Liquid line carries warm or cold liquid

A

Warm

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48
Q

Suction line should slope

A

Down towards condensing unit at quarter inch per foot

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49
Q

Where are refrigerant lines most often damaged

A

Where they pass through the walls of a house

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50
Q

What should you look for when looking for a refrigerant leaks?

A

Oil residue. Refrigerant will boil off.

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51
Q

House air passing across a cold evaporator coil does what

A

Condenses as it cools

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52
Q

Condensate should not discharge below what

A

Into the space below a floor slab

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53
Q

What is the possible issue with adding an AC system to an existing furnace

A

Ductwork designed for heating systems may be undersized

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54
Q

Where are humidifiers mounted?

A

On furnace ductwork, near the AC, between supply and return

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55
Q

Why is a damper needed in humidifier ductwork?

A

For the summer to prevent short-circuiting of the air flow

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56
Q

What is needed when switching between heating and cooling systems

A

Rebalancing of distribution systems by the duct dampers, supply registers, or return grills

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57
Q

Why should the ductwork in attics be insulated?

A

To prevent heat transfer in the attic with a vapour barrier on the outside to prevent condensation

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58
Q

What is the ramification of switching back-and-forth repeatedly from heating and cooling?

A

Can damage compressors

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59
Q

Describe how water cooled AC works

A

Just like air cooled. Coil in house ductwork evaporates a liquid refrigerant into a gas and draws heat out of the house. Gas is compressed to raise temperature.

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60
Q

What is the difference in operation between water cooled AC and air cooled AC

A

Instead of blowing outside air across the gas to cool, it, water is moved across the condenser coil. (doesn’t have to be outside.)

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61
Q

Once water has cooled the gas back into a liquid in a water, cooled AC, what happens to the water?

A

Warm water is disposed and not drinkable

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62
Q

Water cooled coil does the same function as what on air cooled

A

Same function as outdoor coil. Condenses, refrigerant.

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63
Q

Why is recirculating pool water not recommended on water cooled AC

A

Due to corrosion risks from chlorine

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64
Q

What are the three AC system types?

A
  1. Central.
  2. Independent- ducted
  3. Independent.- ductless
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65
Q

In houses with no ductwork, this AC system is added for AC only (no heat)

A

Independent ducted

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66
Q

In an independent duct system, where is the indoor coil located?

A

In the attic

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67
Q

What are the two types of independent ductless AC systems

A

Split system
Single Component system

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68
Q

Describe an AC split system (independent ductless)

A

Condenser cabinet with the compressor, condenser coil, and the fan on the ground or the roof (same as in a central split system)

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69
Q

Where are the evaporator coil and house air fan located in independent ductless split systems

A

Inside the home

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70
Q

Water cooled split systems have these for their interior component

A

Condensate collection and discharge system

71
Q

Water cooled split systems have how many refrigerant lines joining what

A

Two refrigerant lines, joining outdoor condenser unit to evaporator inside the home

72
Q

What are water cooled split systems also called

A

Mini splits

73
Q

Why are split systems quieter?

A

compressor is remote

74
Q

Split systems can be multizone. Up to how many evaporators

A

Four

75
Q

Single component water cooled AC systems are also called

A

Through wall
Package systems

76
Q

Describe a single component AC systems

A

Self contained systems with condenser, compressor, evaporator in the same cabinet

77
Q

Do split systems or single component systems include supplementary heating elements

A

Single component

78
Q

What could be the problem with single component AC systems in small rooms

A

Air can bounce off walls or furniture, and create short cycling

79
Q

Do AC and heat pumps have rated cooling capacity

A

Yes. Both are expressed in tons.

80
Q

How much is a ton of cooling?

A

12,000 BTUs per hour

81
Q

What is one BTU

A

Amount of heat required to raise the temperature of a pound of water by 1°F

82
Q

Typical AC systems are what size

A

Two and 5 ton

83
Q

Cooling systems are sized by

A

Calculating the heat gain for the house

84
Q

Heat gain depends on

A

Climate, size and configuration of house, insulation, types of windows

85
Q

Cooling systems are sized to keep the house

A

15 to 20°F cooler than outdoors

86
Q

AC provides 1 ton of cooling for every
(Moderate climates)
(Hot climates)

A

Moderate= 700 -1000 ft.²
Hot= 450-600 square feet

87
Q

Is it better to undersize or oversize AC and why?

A

Under sizing can perform better because oversizing can short cycle and not remove enough humidity

88
Q

AC life expectancy

A

15 years

89
Q

What is an evaporative cooler?

A

Simple AC that pushes outdoor air into the home after adding water to the air to coolant

90
Q

Where can evaporative cooler be mounted?

A

On the exterior wall or the roof

91
Q

Do evaporative coolers have a return duct

A

No

92
Q

Where are evaporative coolers used?

A

Warm, dry climates (southwest)

93
Q

The high volume low speed blower in evaporative cooler does what

A

Draws outside air into the house through a moist cooling pad. As air passes over wet media, water absorbs heat from the air.

94
Q

Describe the mechanics of evaporative cooler

A

Rotary tank cooler has a metal screen drum that rotates through a tank of water

95
Q

Evaporative coolers don’t work well when

A

The outside air is humid

96
Q

Why should an evaporative cooler not be interconnected with heating duct work?

A

Moist air can cause rot

97
Q

How are central AC systems typically installed

A

In a split system with condenser at building exterior in the evaporator adjacent to the interior furnace equipment

98
Q

Why do some central ACs have electric heaters on compressors?

A

To keep lubricating oil from absorbing refrigerant

99
Q

A reading of what percentages of RLA is normal

A

60 to 90%
More = refrigerant overcharged or bad compressor

100
Q

How high above the ground should be condenser be

A

4 inches

101
Q

Frost on lines or coils could be from

A

Insufficient airflow (filter debris)

102
Q

Where can condensate be discharged?

A

Into laundry, tub, if proper air break is maintained

103
Q

What is suggested to reduce cold air loss?

A

Trap

104
Q

If furnace or evaporator unit is installed in an attic above a finished ceiling, what is necessary

A

A secondary condensate line

105
Q

Evaporator coil should be located where

A

On the down flow side of the heat exchanger

106
Q

Describe heat at a molecular level

A

Molecules bump into each other under pressure, causing heat

107
Q

What is vaporization?

A

Liquid becomes gas
(greatest expansion).
(greatest cooling)

108
Q

What does CFC stand for?

A

Chlorofluorocarbons (banned due to fucking the ozone)

109
Q

Three approved gases

A

Butane, propane, pentane

110
Q

Do fridges or AC create cold

A

No. They move heat.

111
Q

Most critical device on refrigerators, and why

A

Throttling device. (capillary tube.) evaporates liquid.

112
Q

What is the cooling cycle of fridges called?

A

Vapour compression cycle

113
Q

What does COP stand for and what is the equation?

A

Coefficient of performance
Output Divided by Input
(heat absorbed divided by power in)

114
Q

What happens when condensation happens on evaporator coil and what can solve this?

A

Results in frost, impeding process. Heating rods solve this.

115
Q

Where do capillary tubes run on high-efficiency fridges

A

Inside evaporator exit tube

116
Q

Does refrigerant temperature rise in the evaporator?

A

No. It’s phase changes.

117
Q

Why is it necessary for the evaporator exit tube absorb heat?

A

To ensure pure vapour is running back to the compressor. Liquid moves up the capillary tube from the condenser.

118
Q

Describe the function of digital inverter compressor’s

A

Variable speed to avoid shutting on and off
AC converted to DC
Variable frequency to control motor speed

119
Q

What is a ton of cooling?

A

1 ton= 2000 pounds of ice
The amount of heat to melt a ton of ice in 24 hours
(12,000 BTU)

120
Q

What is the equation to come up with 12,000 BTUs for a ton of cooling?

A

144 BTUs per pound
X 2000 pounds
= 288,000 BTU
Divided by 24 hours
=12,000 BTU

121
Q

What is the Latent heat of condensation?

A

Every pound of ice melted (at 32°F or 0°C) that becomes water requires 144 BTUs per pound

122
Q

How many CFM’s per ton on average?

A

400 CFM per ton

123
Q

What is CFM a measurement of?

A

Volume

124
Q

How many cubic feet of air per pound

A

13.33 ft.³.

125
Q

What is specific heat of air?

A

Heat needed to raise temperature of 1 pound of a substance 1°F
(.244 BTU)

126
Q

One cubic foot of air weighs

A

0.741 pounds

127
Q

Why is ice solid?

A

Heat is a form of energy. (molecules in motion.) molecules are in less motion and are somewhat bonded together.

128
Q

Describe sensible heat

A

If heat is added, or removed, it changes the temperature of the substance

129
Q

What is latent heat?

A

If heat is added or removed, it changes the state of the substance

130
Q

Describe saturation

A

When a substance is in the form of both liquid and vapour
If heat is added or removed, it will change state

131
Q

Describe changing state

A

Takes a lot of heat energy
Energy that is either gained or released

132
Q

What is boiling?

A

Changing state (liquid to vapour)

133
Q

What is superheat?

A

Once the liquid has changed completely into vapor, adding more heat will increase the temperature.

134
Q

What is the equation for superheat? (vapour form.)

A

Measured temperature - saturation temperature = superheat (vapour form)

135
Q

What is sub cooling?

A

Once the vapour has changed completely into liquid, removing more heat will decrease temperature

136
Q

What is the equation for sub cooling?

A

Saturation temperature - measured temperature = sub cooling

137
Q

If you compress, a gas, temperature and pressure increase. What happens to its volume?

A

Volume reduces

138
Q

At what state does the liquid move through at the metering device

A

Saturation point (25% vapour 75% liquid)

139
Q

Refrigerant moves through evaporator coil, changing state more and removing heat from air. What point is it at?

A

Latent (50/50)

140
Q

After the evaporator, what heat does the refrigerant pick up

A

Sensible heat (no longer latent) 100% vapour going back to compressor as gas - superheat

141
Q

What kind of heat does refrigerant let off after compressor

A

Sensible heat, condensing back into liquid as fan, cooled it off and dumped into outdoor air

142
Q

What point is refrigerant at through condenser coil?

A

Saturation point until it is liquid

143
Q

How do you figure out AC unit size

A

Model number divided by 12

144
Q

Should you pull out the disconnect while AC unit is running

A

No

145
Q

Possible reasons for icing

A

Low refrigerant, clogged or airflow issue

146
Q

Describe the compressor

A

Converts low pressure low temperature gas to high pressure high temperature

147
Q

Is condensation on a condenser OK?

A

Yes

148
Q

Which is the larger tube on a condenser unit?

A

Suction line. Should be cool and insulated.

149
Q

Describe the evaporator

A

Receives low pressure, low temperature liquid and absorbs heat until all the liquid has been vaporized

150
Q

What is before the evaporator coil and what does it do?

A

Expansion valve reduces pressure temperature in changes to vapour

151
Q

Where is the condensate tray

A

Evaporator coil

152
Q

When in cooling mode, if there is a return on top and bottom floors, which one should you close

A

Bottom one. Reduces cold air being sucked back into return.

153
Q

If return is it outside of the room, what does a gap under the door ensure

A

Room won’t become pressurized and can properly cool

154
Q

These switches turn off compressors as a safety device

A

Pressure sensing switchers

155
Q

Why is a time delay (3-7 mins) on a compressor needed?

A

Time delay after shut off, allows pressure to neutralize because pressure at the discharge side is way higher and suction side is Low

156
Q

What does an accumulator do?

A

Stores liquid refrigerant to prevent it from coming into compressor

157
Q

Approximately how many amps per ton

A

6 to 7

158
Q

What does LRA stand for?

A

Locked rotor amperage (current drawn, if locked) 5-6 times more

159
Q

Are you required to inspect all AC units

A

No. (Window units)

160
Q

Types of heat pumps

A

Water to water
Water to air
Air to air
Bivalent

161
Q

Purpose of emergency heat switch

A

Bypass outdoor temperature sensor

162
Q

Ice builds up on outdoor section of a heat pump because

A

outdoor air has high relative humidity

163
Q

Latent heat point temperature of ice into water

A

0 degrees C or
32 degrees F

164
Q

Latent heat point temperature of water into steam

A

100 degrees C or
212 degrees F

165
Q

Materials that coils are made of

A

Aluminum fins with copper tubing

166
Q

What is latent heat of vaporization?

A

Warm house air boils cold liquid refrigerant into gas at evaporator coil

167
Q

Temperature drop across inside coil after running for 15 minutes

A

15 to 20°F

168
Q

Define slugging

A

When liquid refrigerant enters compressor instead of gas

169
Q

Should evaporator coil be installed upstream or downstream of furnace heat exchanger

A

Downstream. (Not on the return side.)

170
Q

If condensate line is under negative pressure (upstream of blower) what is required

A

Trap

171
Q

Do you close the humidifier damper in the summer or winter?

A

Summer

172
Q

Flexible ducts should be 4 inches away from

A

Hot equipment

173
Q

What is the number for free on

A

R22

174
Q

System where the compressor is in a different location from the outdoor coil are called

A

Triple split

Home Inspection (13 decks)

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