Unit 42

Question 1

What are disadvantages of oversizing equipment

Answer 1

1-cost more to manufacture, purchase, install and maintain
2-cost more to operate because of large motors and other electrical loads
3-requires larger air distribution systems which cost more
4-will cool or heat quicker resulting in more system starts and stops
5-poor dehumidification
6-could increase mold growth

Question 2

Disadvantages of under sizing equipment

Answer 2

1-Will not maintain space temperature
2-long run times
3-power bills go up
4-strips run more in winter

Question 3

In summer we have heat blank to the structure

Answer 3

Gain

Question 4

In the winter we have heat blank to the structure

Answer 4

Loss

Question 5

To size equipment properly the process is called

Answer 5

Heat loss heat gain Manual J

Question 6

2 methods of calculations used on structures

Answer 6

Total envelope and room by room

Question 7

Why do we perform load calculations on houses

Answer 7

To have proper size heating and air systems

To match the house for temperature and humidity requirements

Question 8

What is the rule of thumb for sizing HVAC systems in this area

Answer 8

600 square feet per ton

Question 9

Name 4 things that must be considered before a load is done on the structure

Answer 9

How accurate for the result have to be
How accurate does the temperature control need to be
How critical does the humidity control need to be
Is an equipment rebate being applied for

Question 10

Give 6 disadvantages in using a rule of thumb to size your HVAC equipment

Answer 10

Does not take into account the geographic location of the house
Type of material used in construction
Slope of the roof and the color of the roof and materials
Orientation of the hous
Types of windows and doors
Number of windows and doors

Question 11

What is the disadvantage of using the manufacturers equipment simplified load sheet

Answer 11

May not be accepted where rebates are involved

Question 12

What is the most accepted form of heat gain, heat loss in our industry

Answer 12

Manual J

Question 13

What kind of problems could come about from a poor system design and end up in court

Answer 13

Could have structure damage
Mold related issues
Health related issues

Question 14

Factors needed to calculate a load on a structure would be

Answer 14

The difference between the indoor and outdoor temperature

Type of construction materials used

Question 15

The indoor design temperature for manual j for heating and cooling is

Answer 15

Heating-70

Cooling-75

Question 16

What is design temperature for the summer and winter

Answer 16

Summer
Indoor-75
Outdoor 95

Winter
Indoor-70
Outdoor-24

Question 17

What is the daily range

Answer 17

The average difference between the daily high and daily low temps for a given location

Question 18

R value shows what

Answer 18

Thermal resistance of insulation materials, higher r values harder for heat to pass through

Question 19

R value of 38 gives what U value

Answer 19

.026 1/38

Question 20

How is the U value expressed

Answer 20

BTU’s per hour per degree Fahrenheit per square foot

Question 21

List areas that heat can be gained or lost through the structure

Answer 21

Exposed walls, windows, doors, roofs, ceiling cavaliers, partition panels, below grade walls, slab and basement floors, floors above unconditioned spaces, cracks in the structure

Question 22

What is sheathing

Answer 22

Relatively thin panel installed on the outside of the wall or roof framing and covered by brick, stone, siding or shingles

Question 23

What is the gross wall area

Answer 23

Area of a wall before any windows or doors are cut into it

Question 24

What is the net wall area

Answer 24

A term used to describe the area of the wall after the doors and windows are cut into the wall

Question 25

What is the formula for heat transfer

Answer 25

Q= U value x TD x Area

Question 26

Define the term below grade

Answer 26

Walls or portions of a wall that are below ground level

Question 27

The term slab on grade is

Answer 27

The house is on a slab which is on ground level

Question 28

Insulation around the perimeter is expressed in blank and not U values

Answer 28

F values which is btus per running door per degree Fahrenheit

Question 29

What does the 1.08 represent in the CFM formula

Answer 29

It is a constant, 1.08xCFMxTD. Is an estimate of how many cubic feet of air are entering the structure each minute

Question 30

ACH stands for

Answer 30

Air changes per hour

Question 31

How do we determine the volume of a house

Answer 31

LxWxH. Once you find the CFMs then use formula 1.08xCFMxTD

Question 32

The rate at which heat loss happens as air passes through a duct in an unconditioned space is determined by

Answer 32

Temperature of air in the duct
Temperature of the air in the unconditioned space
Amount of insulation on the duct work

Question 33

What other internal heat gain do we have in a structure

Answer 33

Occupants
Appliances
Lighting
Plants
Fish tanks
Other heat generating elements

Question 34

Heat gain can occur in many ways which are

Answer 34

Through exposed walls
Through doors
Through roofs, walls, floors and ceilings
Through windows 
From people, appliances, lighting
Through cracks in structure
Through duct runs through attic

Question 35

The sum of heat gain on a structure is

Answer 35

Conduction Loads
Internal loads
Solar loads
Infiltration loads

Question 36

Two things that are important when getting the heat gain factors for windows

Answer 36

Make sure you’re using the correct table

Get the correct orientation of the windows

Question 37

List other things that would impact the solar load on the house

Answer 37

Amount of shading
Overhangs
Extras on the window itself
Internal shading

Question 38

When we are calculating heat gain what is the estimate figure we use for people

Answer 38

Number of bedrooms plus 1

Question 39

How many BTUs of sensible and latent is used for people

Answer 39

Total heat gain is 430 BTUs
Sensible 230 BTUs
Latent 200 BTUs