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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
If a supply air branch measures more than fifty feet in length what should be done to the cfm allowed for this register ?
Should be sized 10% more airflow (cfm) than which was allowed for this diffuser
26
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 ?
Install zone systems
27
Where can u find the combustion and dilution air requirements ?
Csa Cga Equitment insulation codes Provincial codes
28
What is important to remember when locating supply air outlets ?
Always one exposed wall or window must be bathed with warm air from a supply outlet
29
What is the recommended maximum cfm per register ? (Supply)
100cfm 3kw 10,000 btuh
30
Where should the outlets be located for a heating and cooling system ?
Outer perimeter and should bathe atkeast one exterior wall
31
Which type of rooms would not have a perimeter outlet?
Kitchens bathrooms and utility rooms
32
What should be installed in the supply air outlets that are located in finished areas ?
Provide diffuser with an adjustable air damper for supply outlets that are installed in a finished areas
33
If a branch line does not have an adjustable diffuser what must be done to the branch line ?
Adjustable damper installed on branch and must have indacator that shows positions of the damper
34
How far off the exterior walls should a supply outlet be located ?
8”
35
Why would we install supply air outlets away from exterior walls as opposed to haveing them flush with the exterior wall?
So they do not interfere with the drapes
36
Where should supply air outlets be placed in an entry way ?
Where no one can walk on the outlet
37
When would a walk in closet be required to have a supply air outlet?
When it has a heat loss greater than 1000BTUH
38
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 ?
Added into the adjacent room
39
How many supply air outlets are needed for a crawl space ?
Enough to distribute heat evenly and to compensate for heat loss
40
What must be installed in a crawl space supply air ?
Diffuser or lockable damper
41
How many supply registers are required for an unfinished basment ?
Must have atkeast one supply air outlet for every 430ft squared of the floor area
42
Where should return air inlets be located to avoid short circuiting of the warm air in a residential home ?
Centrally or on the interior walls should
43
Where are return air inlets generally located in a residential application?
Lower wall or in the floor
44
Why would we want to install a high low return air inlet ?
For instances that use heating and cooling
45
What are the minimum code requirements for return air inlets in a home ?
One return air inlet be provided on each floor
46
What would be the advantages to having more than minimum code requirements for return air inlets in a house?
Eliminates cold drafts No need for undercutting doors Eliminates temp differences
47
What are theee ways to return air from a room in a house ?
Return air in room Door grille Undercut doors
48
What are theee ways to return air from a room in a house ?
Return air in room Door grille Undercut doors
49
How much return air should be moved on each floor of a house
The total volume of air supplied to the level besides the basment only 50%
50
Why is it good trade practice to only return 50% of the supply air back to the duct system in a basement?
Ensure it will keep a positive pressure and may help to prevent back drafting of natural draft appliances
51
Where should the remainder of the return air be taken from ?
Uppermost level
52
List 5 room types that return air inlets should not be installed in ?
Kitchens Bathrooms Laundry rooms Utility rooms Enclosed crawl spaces
53
List 5 room types that return air inlets should not be installed in ?
Kitchens Bathrooms Laundry rooms Utility rooms Enclosed crawl spaces
54
Why do the 5 rooms not get return airs in them?
Undesirable odours and moisture that could spread throughout the house
55
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 ?
May allow sound and or light to travel room to room
56
Why can a vertical return air duct not serve more than one floor in a residential application
Prevent cold air from travelling from one floor to another
57
How is ventilation air introduced into a house ?
Ducting of some type
58
What two things must be considered when Introducing fresh air into a residential hvac system ?
Fresh air inlet size Mixed air temp
59
What requirements must be met when installing a ventilation air inlet connection to an hvac duct system ?
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
What should be installed in a fresh air duct to control the proper amount of ventilation air into a home ?
Damper
61
At what mixes air tempature could you possibly void the warranty on a heating appliance?
60 degrees F 16 degrees C
62
What two things must be done first before you can design a duct system properly ?
Calculate heat loss and heat gain
63
What are some examples of components that a furnaces blowers external static pressure must over come?
Filters Coils Ducts
64
Where can we find the pressure drop or losses needed to design a heating/cooling system?
Manufactures spec sheets
65
What must be done to a heating appliance that is located in an area that could be considered high altitude ?
Derate the furnace
66
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 ?
Wet because it is always the greater of the two
67
Why must we account for accessories added to the plenum or main trunk duct ?
They cause pressure drops
68
Why is it important to know the availabile design pressure v
It’s the factor that is used to overcome the resistance of both the supply and return air systems
69
What must be included when calculating the available design pressure ?
All grilles and diffusers
70
What is the maximum amount of cfm that a 2”x4” wall can draw through the floor to joist opening ?
120cfm
71
What is the maximum amount of cfm that a 2”x6” wall can draw through the floor to joist openings ?
180cfm
72
What causes turbelence in a return air duct ?
Merging of two seperate airstreams
73
What are the two joists to trunk opening sizes that are recommended to be cut in the top of return air duct ?
2”x4” = 7”x14” 2”x6”= 11”x14”
74
What is the minimum joist to trunk opening recommended in this module ?
Never less than 1.5 times the branch area
75
When selecting duct sizes what three things should be considered ?
Duct aspect ratio Space duct must fit in Streamline of the duct
76
When should trunk duct be transited for return air ?
When main trunk collects approximately 50% of air volume has been distributed If two reducers 33%
77
Is aspiration supply or return?
Supply
78
Is turbelence supply or return ?
Return
79
How many btu per kw ?
3410 btu per kw
80
On a heat pump what kind of valve is used ?
4 way reversing valve
81
What can be the advantage when you are required to perform a detailed residential duct design to help organize your data ?
Worksheet and instructions
82
What can be the advantage when you are required to perform a detailed residential duct design to help organize your data ?
Worksheet and instructions
83
For small offices what is the velocity recommended ?
500fpm to 700fpm

Third Year (10 decks)

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