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Third Year > Comercial Hvac Systems > Flashcards

Comercial Hvac Systems Flashcards

1
Q

How could a constant volume best be described in relationship to air flow and temperature ?

A

The supply airflow rate is constant but the supply air tempature is varied to meet the thermal loads of the space

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2
Q

Where would you see a constant air volume system ?

A

Restaurants
Offices
Apartments
Supermarkets
Libraries
Plants
Labs
Schools

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3
Q

What are some system variations for constant air volume systems

A

Reheat
Multizone
Primary secondary

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4
Q

Why are constant air volume systems often the systems of choice ?

A

Simplicity
Low cost
Reliability

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5
Q

What does vav mean

A

Variable air volume

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6
Q

What does vav mean

A

Variable air volume

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7
Q

What are two main styles of vav systems

A

Regular
True

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8
Q

How do the two styles of vav differ ?

A

Regular dosent change speed of fans like true ones do

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9
Q

What reduces energy consumption in by fans in a vav system ?

A

Fan capacity control

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10
Q

How many air inlets are there on a single supply vav box ?

A

One

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11
Q

How many air inlets are there on a single supply vav box ?

A

One

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12
Q

Where do the two air streams mix in a dual duct vav system

A

Mixing box

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13
Q

Describe how dual duct system can provide better airflow to the conditioned space than a single duct system ?

A

Single duct has damper regulating airflow
Dual duct has constant air flow

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14
Q

How does the air volume vary in a bypass system ?

A

System bypasses the supply outlets and dumps or cycles the excess air into return air duct or plenum ceiling instead of Accutalky throwing down the air

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15
Q

True or false

Reheat coils are either hot water or electric coils and are usually installed in or close to zone they serve ?

A

True

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16
Q

What controls the amount of air and its tempature delieverd to each zone in a multizone system ?

A

Two section dampers

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17
Q

For higher velocity air systems how is air velocity slowed down before entering the conditioned space ?

A

Attenuator box

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18
Q

Where are induction reheat systems often found ?

A

Mounted beneath windows in institutional buildings such as hospitals

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19
Q

Why do most buildings exhaust air systems require a make up air unit ?

A

So they are not under negative pressure

20
Q

List the two types of gas fired make up air units ?

A

Direct
Indirect

21
Q

How do indirect and direct muas differ ?

A

Indirect has sealed combustion chamber so all products of combustion go outside and direct has the products of combustion become a part of mua and discharge into the building

22
Q

What type of air system is usually paired with most gas fired make up air units ?

A

Exhaust system

23
Q

What are the three main applications for direct fired make up air units ?

A

Makeup air heating or cooling
Space heating
Space pressure control

24
Q

Four gases from combustion are discharged out door through the flue in a direct fired make up gas unit
(True or false )

A

False

25
Q

Must the exhaust air and makeup air systems be interlocked ?

A

Yes due to building code

26
Q

What are the two main categories of commercial hvac systems ?

A

Constant air volume
Variable air volume

27
Q

List four types of vav systems

A

Single duct
Dual duct
Bypass
True vav

28
Q

Vav systems are preferred because of Thier energy saving capabilities ?

A

True

29
Q

Single duct vav systems adjust the volume of the air entering the space ?
(True or false )

A

True

30
Q

Dual duct vav systems blend the cooled and heated air at the air handling unit and then distribute it through the ductwork to the terminal units ?
(True or false )

A

False

31
Q

A dual duct system maintains the tempature in the space by what ?

A

Increasing or decreasing the quantity of heated or cooled air

32
Q

The bypass vav system uses _______ to control the space tempature .

A

The opening or closing of a volume damper

33
Q

A true vav system varies the ___________ to control the temperature in a space.

A

Air volume

34
Q

What is the air temperature that is delivered from the central air handling unit in a cvs?

A

55 degrees Fahrenheit
1 degree C

35
Q

What does cv-vt mean ?

A

Constant volume varying tempature

36
Q

What tempature is air delivered at in a cvs single zone reheat system ?

A

55 degrees F
1 degrees C

37
Q

Describe the difference between multizones and a three deck multizone system ?

A

Three deck has a third air stream that is neather heated nor cooled

38
Q

What are make up air units used for ?

A

Replace the air that is expelled by a buildings exhaust system

Can provide heat and cooling too

39
Q

A direct fired makeup air unit that can utilize return air is called a ?

A

Recirculating direct fired makeup air unit

40
Q

Why are cav systems the often system of choice in small buildings and residences ?

A

Simplicity
Low cost
Reliability

41
Q

How are the airflow roles to individual zones controlled in a true vac system

A

Variable speed supply fan

42
Q

What can be a result of a fan over pressurizing a supply air duct

A

Duct sealing can be damaged

43
Q

What is the main benefit of a regular variable air volume system

A

Conserves energy

44
Q

In a single duct vac system what happens to the supply airflow rates as the zone becomes cooler

A

Airflow to the zone decreases

45
Q

In a single duct vac system what happens to the supply airflow rates as the zone becomes cooler

A

Airflow to the zone decreases

46
Q

What type of commercial hvac system reduces output at the fan with either inlet vanes or centrifugal fans or with variable pitch vane axial fans ?

A

True vav systems

47
Q

What is the advantage of installing a high velocity system ?

A

Les’s requires felling space for ductwork

Third Year (10 decks)

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