Comercial Hvac Systems

Question 1

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

Answer 1

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

Question 2

Where would you see a constant air volume system ?

Answer 2

Restaurants
Offices
Apartments
Supermarkets
Libraries
Plants
Labs
Schools

Question 3

What are some system variations for constant air volume systems

Answer 3

Reheat
Multizone
Primary secondary

Question 4

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

Answer 4

Simplicity
Low cost
Reliability

Question 5

What does vav mean

Answer 5

Variable air volume

Question 6

What does vav mean

Answer 6

Variable air volume

Question 7

What are two main styles of vav systems

Answer 7

Regular
True

Question 8

How do the two styles of vav differ ?

Answer 8

Regular dosent change speed of fans like true ones do

Question 9

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

Answer 9

Fan capacity control

Question 10

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

Answer 10

One

Question 11

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

Answer 11

One

Question 12

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

Answer 12

Mixing box

Question 13

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

Answer 13

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

Question 14

How does the air volume vary in a bypass system ?

Answer 14

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

Question 15

True or false

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

Answer 15

True

Question 16

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

Answer 16

Two section dampers

Question 17

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

Answer 17

Attenuator box

Question 18

Where are induction reheat systems often found ?

Answer 18

Mounted beneath windows in institutional buildings such as hospitals

Question 19

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

Answer 19

So they are not under negative pressure

Question 20

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

Answer 20

Direct
Indirect

Question 21

How do indirect and direct muas differ ?

Answer 21

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

Question 22

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

Answer 22

Exhaust system

Question 23

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

Answer 23

Makeup air heating or cooling
Space heating
Space pressure control

Question 24

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

Answer 24

False

Question 25

Must the exhaust air and makeup air systems be interlocked ?

Answer 25

Yes due to building code

Question 26

What are the two main categories of commercial hvac systems ?

Answer 26

Constant air volume Variable air volume

Question 27

List four types of vav systems

Answer 27

Single duct Dual duct Bypass True vav

Question 28

Vav systems are preferred because of Thier energy saving capabilities ?

Answer 28

True

Question 29

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

Answer 29

True

Question 30

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 )

Answer 30

False

Question 31

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

Answer 31

Increasing or decreasing the quantity of heated or cooled air

Question 32

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

Answer 32

The opening or closing of a volume damper

Question 33

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

Answer 33

Air volume

Question 34

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

Answer 34

55 degrees Fahrenheit 1 degree C

Question 35

What does cv-vt mean ?

Answer 35

Constant volume varying tempature

Question 36

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

Answer 36

55 degrees F 1 degrees C

Question 37

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

Answer 37

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

Question 38

What are make up air units used for ?

Answer 38

Replace the air that is expelled by a buildings exhaust system Can provide heat and cooling too

Question 39

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

Answer 39

Recirculating direct fired makeup air unit

Question 40

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

Answer 40

Simplicity Low cost Reliability

Question 41

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

Answer 41

Variable speed supply fan

Question 42

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

Answer 42

Duct sealing can be damaged

Question 43

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

Answer 43

Conserves energy

Question 44

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

Answer 44

Airflow to the zone decreases

Question 45

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

Answer 45

Airflow to the zone decreases

Question 46

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 ?

Answer 46

True vav systems

Question 47

What is the advantage of installing a high velocity system ?

Answer 47

Les’s requires felling space for ductwork