Commercial Hvac Systems Flashcards
Two types of Hvac systems are
CAV
VAV
CAV systems are small and serve single thermo zone name variations
CAV with reheat coil
CAV multizone
CAV primary secondary system
What are the too Main style VAV systems 
Regular VAV
True vAV
How do you explain the two styles of VAV
Regular system does not change speed of fans
VAV system has fan capacity control and D humidification
What reduce energy consumption by and Vav system.?????????????
Check your book for correct
In modern systems of verbal fan capacity control reduces the energy
VAV systems also allow for smaller sizing of fans and heating and cooling equipment true or false
True
What temperature is delivered at constant vav system 
55 f
13 c
What happens when minimal airflow is reached for zones
Reheat coil or baseboard heater is activated
How could a constant volume system best be described in relationship to airflow and temperature
Constant air volume will supply constant airflow but the air temperature is varied to meet the thermal loads of occupied space
Provide some applications for constant air volume system
Restaurants apartments libraries plants schools
What are some system variations for constant air volume
CAV with heat reheat coil
Multi zones
Primary secondary
Why are constant air volume systems often the system of choice
They are the system of choice for small buildings because of simplicity low-cost and reliable
What are two main styles of VAV systems
Regular VAV system
True VAV system
What reduces consumption in VAV system
In modern systems fan are variable which reduces energy
How do you the two styles of VAV systems differ
Regular system does not change speed but uses dampers to control the air quality
True VAV systems can reduce fan capacity and dehumidification
How many inlets are in a single Supply VA box
One
How does a single duct VAV system differ from a dual duct VAV system
The single VAV is designed with volume control damper
Dual system has two separate supply air ducts and airflow maybe 50% less in cooling
Where do the two airstreams mix and a dual duct VAV system
The two airstreams mix in the mixing box serving the thermal zone
How does the air volume vary in a bypass system
Volume in the bypass varies air in the space by cycling unwanted conditioned air back to the central air unit without allowing it to pass through the occupied space
What type of air system is usually paired with most gas-fired make up air units
Make up air system
Name three applications for direct fired make up air unit
Commercial kitchen auditoriums airports
Flue gases from combustion or discharge outdoors through in a indirect fired and make up air units true or false
False
Must the exhaust air and make up air systems be interlocked
Yes
What controls the amount of air and his temperature delivered to each multi zone system
Each system has two dampers cold deck hot deck and is controlled by thermostat from occupied space
Where are induction reheat systems often found
Under windows where they can be offset a cold draft in winter months
Why do you most buildings exhaust air systems require make up our system
Because large volumes of air are being removed It needs to be replaced so It don’t create negative pressures
Two types of gas-fired make up air units
Direct gas fired
Indirect gas fired
How do two types of MUA systems differ
Direct gas Fired has burner directly in the make up airstream and products of combustion become part of the make up air
Indirect gas fire has a sealed combustion which all products of combustion are centred into the environment
List four Types of VAV system
Single duct
Dual duct
Bypass
True VAV
Single duct VAV systems adjust volume of air entering the space true or false
True
A true VAV system varies………To control the temperature in the space
Air volume
A direct fired make up air unit can utilize return air is called
Recirculation direct fired make up air unit
