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Third Year > Residential Hvac Design > Flashcards

Residential Hvac Design Flashcards

1
Q

The output of of heating equitment should be ?

A

100% to 140% of the houses total heat loss

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2
Q

The output of cooling equitment should be?

A

80%to 125% of the houses total heat gain

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3
Q

List four factors that you must consider when designing an hvac system ?

A

Proper duct size

Ducts running through uncondioted
space

Zoning for houses with special heating and cooling needs

Combustion and dilution air

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4
Q

What must be done to a duct that runs through an unconditioned space ?

A

Insulate the duct

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5
Q

How far away from the wall should a supply air outlet be located ?

A

8”

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6
Q

What is the minimum number of return air inlets allowed per floor ?

A

1

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7
Q

How much return air should be collected from the basment ?

A

50% of the supply airflow to the basement

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8
Q

List five areas where return air may not be installed

A

Kitchens
Bathrooms
Laundry rooms
Utility rooms
Enclosed crawl spaces

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9
Q

What is the heating airflow proportioning factor ?

A

the cfm required to deliver one btuh of heat at the heating flow rate

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10
Q

Where would u find the heating load for each room when performing a duct design for a regular job ?

A

Heat loss/gain calculation sheets

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11
Q

Is it considered good trade practice to have more than one return air inlet per floor ?
(True or false)

A

True

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12
Q

Which branch run is used to determine esp apportioning factor ?

A

Supply

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13
Q

What is the acceptable air velocity for the main supply air trunk ?

A

700fpm to 900fpm

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14
Q

Before selecting a furnace or ac unit for a residence what must be done first ?

A

Heat loss calc

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15
Q

One ton of cooling equals how many btuh

A

12000 btuh

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16
Q

When calculating air flow rates for cooling what are the manufacturers recommended air flow rates ?

A

400cfm per ton of cooling

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17
Q

What three factors is airflow rates based on ?

A

Heating cfm
Cooling cfm
Act

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18
Q

With heating cfm cooling cfm and act what do we do our duct design off of ?

A

The largest out of the three

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19
Q

When designing an hvac system what must it be designed to meet ?

A

Local building codes and standards

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20
Q

List four factors that must be considered when designing a residential hvac system?

A

Proper duct size
Ducts running through unconditioned spaces
Zoneing for houses with special heating and cooling
Combustion and dilution air

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21
Q

When sizing ductwork why is it important that the volumes stay within a certain range ?

A

Comfortable air circulation within the appropriate temp rise for the selected equipment

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22
Q

What must be done to a duct that passes through an unconditioned space ?

A

Sealed air tight with tape or sealer and insulated

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23
Q

Where should the vapour barrier be placed when insulating a duct and why ?

A

Warm side of the insulation to prevent condensation

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24
Q

Where should the vapour barrier be placed when insulating a duct and why ?

A

Warm side of the insulation to prevent condensation

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25
Q

If a supply air branch measures more than fifty feet in length what should be done to the cfm allowed for this register ?

A

Should be sized 10% more airflow (cfm) than which was allowed for this diffuser

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26
Q

What should be done when designing a residential hvac system in a home that has large differences in the heat loss or heat gain in diffrent areas ?

A

Install zone systems

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27
Q

Where can u find the combustion and dilution air requirements ?

A

Csa
Cga
Equitment insulation codes
Provincial codes

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28
Q

What is important to remember when locating supply air outlets ?

A

Always one exposed wall or window must be bathed with warm air from a supply outlet

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29
Q

What is the recommended maximum cfm per register ? (Supply)

A

100cfm
3kw
10,000 btuh

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30
Q

Where should the outlets be located for a heating and cooling system ?

A

Outer perimeter and should bathe atkeast one exterior wall

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31
Q

Which type of rooms would not have a perimeter outlet?

A

Kitchens bathrooms and utility rooms

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32
Q

What should be installed in the supply air outlets that are located in finished areas ?

A

Provide diffuser with an adjustable air damper for supply outlets that are installed in a finished areas

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33
Q

If a branch line does not have an adjustable diffuser what must be done to the branch line ?

A

Adjustable damper installed on branch and must have indacator that shows positions of the damper

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34
Q

How far off the exterior walls should a supply outlet be located ?

A

8”

35
Q

Why would we install supply air outlets away from exterior walls as opposed to haveing them flush with the exterior wall?

A

So they do not interfere with the drapes

36
Q

Where should supply air outlets be placed in an entry way ?

A

Where no one can walk on the outlet

37
Q

When would a walk in closet be required to have a supply air outlet?

A

When it has a heat loss greater than 1000BTUH

38
Q

If a walk in closet is not required to have a supply air where would we add the heat loss that is needed to actually heat this room ?

A

Added into the adjacent room

39
Q

How many supply air outlets are needed for a crawl space ?

A

Enough to distribute heat evenly and to compensate for heat loss

40
Q

What must be installed in a crawl space supply air ?

A

Diffuser or lockable damper

41
Q

How many supply registers are required for an unfinished basment ?

A

Must have atkeast one supply air outlet for every 430ft squared of the floor area

42
Q

Where should return air inlets be located to avoid short circuiting of the warm air in a residential home ?

A

Centrally or on the interior walls should

43
Q

Where are return air inlets generally located in a residential application?

A

Lower wall or in the floor

44
Q

Why would we want to install a high low return air inlet ?

A

For instances that use heating and cooling

45
Q

What are the minimum code requirements for return air inlets in a home ?

A

One return air inlet be provided on each floor

46
Q

What would be the advantages to having more than minimum code requirements for return air inlets in a house?

A

Eliminates cold drafts
No need for undercutting doors
Eliminates temp differences

47
Q

What are theee ways to return air from a room in a house ?

A

Return air in room
Door grille
Undercut doors

48
Q

What are theee ways to return air from a room in a house ?

A

Return air in room
Door grille
Undercut doors

49
Q

How much return air should be moved on each floor of a house

A

The total volume of air supplied to the level besides the basment only 50%

50
Q

Why is it good trade practice to only return 50% of the supply air back to the duct system in a basement?

A

Ensure it will keep a positive pressure and may help to prevent back drafting of natural draft appliances

51
Q

Where should the remainder of the return air be taken from ?

A

Uppermost level

52
Q

List 5 room types that return air inlets should not be installed in ?

A

Kitchens
Bathrooms
Laundry rooms
Utility rooms
Enclosed crawl spaces

53
Q

List 5 room types that return air inlets should not be installed in ?

A

Kitchens
Bathrooms
Laundry rooms
Utility rooms
Enclosed crawl spaces

54
Q

Why do the 5 rooms not get return airs in them?

A

Undesirable odours and moisture that could spread throughout the house

55
Q

Why is it not good trade practice to install two return air grills back to back on a wall to draw air from two rooms ?

A

May allow sound and or light to travel room to room

56
Q

Why can a vertical return air duct not serve more than one floor in a residential application

A

Prevent cold air from travelling from one floor to another

57
Q

How is ventilation air introduced into a house ?

A

Ducting of some type

58
Q

What two things must be considered when Introducing fresh air into a residential hvac system ?

A

Fresh air inlet size
Mixed air temp

59
Q

What requirements must be met when installing a ventilation air inlet connection to an hvac duct system ?

A

Connection shall be between the nearest return air branch connection and the blower

Connection shall be at least 10’ from blower or connected useing an acceptable mixing device

60
Q

What should be installed in a fresh air duct to control the proper amount of ventilation air into a home ?

A

Damper

61
Q

At what mixes air tempature could you possibly void the warranty on a heating appliance?

A

60 degrees F
16 degrees C

62
Q

What two things must be done first before you can design a duct system properly ?

A

Calculate heat loss and heat gain

63
Q

What are some examples of components that a furnaces blowers external static pressure must over come?

A

Filters
Coils
Ducts

64
Q

Where can we find the pressure drop or losses needed to design a heating/cooling system?

A

Manufactures spec sheets

65
Q

What must be done to a heating appliance that is located in an area that could be considered high altitude ?

A

Derate the furnace

66
Q

When calculating the pressure drop on an air conditioning coil, there will always be a wet and dry value, which if the two will we use in our calculations and why ?

A

Wet because it is always the greater of the two

67
Q

Why must we account for accessories added to the plenum or main trunk duct ?

A

They cause pressure drops

68
Q

Why is it important to know the availabile design pressure v

A

It’s the factor that is used to overcome the resistance of both the supply and return air systems

69
Q

What must be included when calculating the available design pressure ?

A

All grilles and diffusers

70
Q

What is the maximum amount of cfm that a 2”x4” wall can draw through the floor to joist opening ?

A

120cfm

71
Q

What is the maximum amount of cfm that a 2”x6” wall can draw through the floor to joist openings ?

A

180cfm

72
Q

What causes turbelence in a return air duct ?

A

Merging of two seperate airstreams

73
Q

What are the two joists to trunk opening sizes that are recommended to be cut in the top of return air duct ?

A

2”x4” = 7”x14”
2”x6”= 11”x14”

74
Q

What is the minimum joist to trunk opening recommended in this module ?

A

Never less than 1.5 times the branch area

75
Q

When selecting duct sizes what three things should be considered ?

A

Duct aspect ratio
Space duct must fit in
Streamline of the duct

76
Q

When should trunk duct be transited for return air ?

A

When main trunk collects approximately 50% of air volume has been distributed

If two reducers 33%

77
Q

Is aspiration supply or return?

A

Supply

78
Q

Is turbelence supply or return ?

A

Return

79
Q

How many btu per kw ?

A

3410 btu per kw

80
Q

On a heat pump what kind of valve is used ?

A

4 way reversing valve

81
Q

What can be the advantage when you are required to perform a detailed residential duct design to help organize your data ?

A

Worksheet and instructions

82
Q

What can be the advantage when you are required to perform a detailed residential duct design to help organize your data ?

A

Worksheet and instructions

83
Q

For small offices what is the velocity recommended ?

A

500fpm to 700fpm

Third Year (10 decks)

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