VAVs Part II
What does VAV stand for?
Variable Air Volume
What does the letters AHU mean?
Air handling Unit
Industry standard setpoint for DA-T?
55 deg F
What is duct static pressure?
Static pressure is the force exerted by air on all sides of the ductwork
Which component on the VAV is responsible for calculating air flow?
The duct pitot tubes which convert static pressure to air flow
What component of the VAV system controls the amount of air flow distributed to the space?
Supply Air Damper
List the 6 basic mechanical components of a basic AHU?
SF
RF
HTG Coil
CLG Coil
Filter
Dampers - OA and RA
Definition of return air?
Air from the space / building being re-used / mixed w Outdoor air
What is the 3 main functions of an AHU?
Clean / sanitize air
Temper the air
Distribute the air
A cooling only VAV box uses which component to heat / warm the zone or space?
Supply Air Damper
Where does the VAV receive is supply air from?
AHU
If conditions are favorable, OA is used to cool space / building. This process is known as?
Free Cooling / Economizing
Industry standard setpoint for DA static pressure?
1.5 in wc
The sensor before the HTG / cooling coils and before the filters. Averaging type sensor
Mixed Air Temperature
What are 4 main flow setpoints of the VAV Box?
HTG MIN
HTG MAX
CLG MIN
CLG MAX
What attribute in programming / logic is used in conjunction w/ box size to calculate flow setpoints?
k-Factor
What two can you identify if the OA and RA dampers are mechanically linked?
Visually verifying the damper linkage
In control logic, if only 1 output is configured normally labeled MAD-O, these indicate that the dampers are mechanically linked
Device that sends / receives electrical signals to / from field equipment to efficiently operate mechanical HVAC systems?
Field Device
What is mixed air?
The air that has returned from the building or space and mixed with the incoming OA
What device is used to report space / zone conditions to the VAV field device?
NetStat
Zone Temp
Thernostat
Of the 4 flow setpoints, which two are always the same value and why?
HTG MAX and CLG MIN
The same due to box switching from HTG to CLG mode flow setpoint stays the same but HTG is disabled
What is the definition of discharge air?
Air that has been treated and ready for distribution to the space / building
5 types of VAV boxes
VAV reheat
Cooling Only
Series fan
parrallel Fan
VAV w electric heat
Switch used to shutdown AHU on safety to protect mechanical equipment from damage - specifically freezing of coils?
Low temp Cutout / alarm
Which component of the VAV system determines the STATE or which 4 of the airflow setpoints are in use?
Network Stat
Thermostat
Zone Temperature