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Variable Air Volume Distribution Units
CII, September 1st, 2010
HomeVAV – It’s All About Measuring Airflow
Accurate air flow measurement allows you to:
Provide the absolute minimum air flow needed for ventilation.
Use a larger sized box to reduce air
pressure drop in the system.
Ensure that the controller has an accurate
signal, which gives your system the
capability to feed only the needed CFM.
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Amplified Velocity Pressure
Averaged Pressure Output
Abated Noise & Pressure Drop
HomeAccurate Air Flow Traverse
Look To
ASHRAE 2001 Fundamentals Page 14.17
Measuring Flow in Ducts –
that’s what we did to design our Flowstar™
Airflow Sensor
Figure 6 - Measuring Points for Round Duct
Traverse
Log-linear Rule for Circular Ducts
Provides specific measuring point locations for
6, 8, and 10 measuring point per diameter
configurations
HomeFlowStarTM Airflow Sensor
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Equal concentric measurement
points per AHRAE Fundamentals
Amplified Velocity Pressure
Averaged Pressure Output
Abated Noise & Pressure Drop
Does this look familiar?
HomeAmplified Velocity Pressure
What is Velocity Pressure (Pv)?
THE
CONTROLLER’S
DIFFERENTIAL
PRESSURE
SENSOR
The controller’s differential pressure sensor measures the difference between
the TOTAL pressure (Pt) and the STATIC pressure (Ps).
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Why amplify velocity pressure?
Because all differential pressure sensors
have a minimum differential pressure,
below which they lose control.
(typically 0.015” wg)
Amplification allows the controller to react
to lower air flows, since the differential
pressure transducer still sees a
measureable difference.
Compare the differential pressure reading for the same
airflow to a typical pitot sensor:
CFM(Size 8) FPM Pv(Pitot) dP(FlowStar)
1000 (max) 2865 0.56”w.g. 1.50”w.g.
800 (typ.) 2400 0.36”w.g. 0.99”w.g.
160 (20%) 480 0.015”w.g. 0.04”w.g.
Amplified Velocity Pressure
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FlowStarTM Airflow Sensor
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Equal concentric measurement points per
AHRAE Fundamentals
Amplified Velocity Pressure
Pv amplified 230 to 290%
Averaged Pressure Output
Abated Noise & Pressure Drop
HomeAveraged Pressure Output
Problems with the Non-Averaging Method
The signal from the ports closest to the connectors are vastly overweighted.
The tubes from the connector to the center point must be perfectly matched –any difference in length will reduce accuracy.
HomeFlowStarTM Airflow Sensor
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Equal concentric measurement points per
AHRAE Fundamentals
Amplified Velocity Pressure
Pv amplified 230 to 290%
Averaged Pressure Output
Center averaging on all units
Abated Noise & Pressure Drop
HomeAbated Noise and Pressure Drop
Scaled Drawing - Size 8 Inlet Collar
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Lower Percentage of Free Area Causes:
Higher Air Velocity
More Pressure Drop
More Noise
Abated Noise and Pressure Drop
HomeFlowStarTM Airflow Sensor
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Equal concentric measurement points per
AHRAE Fundamentals
Amplified Velocity Pressure
Pv amplified 230 to 290%
Averaged Pressure Output
Center averaging on all units
Abated Noise & Pressure Drop
Precision-machined aircraft grade aluminum
tubes
HomeFlowStarTM Airflow Sensor
The four “A’s” of accurate air flow
measurement:. .
Accurate Airflow Traverse
Equal concentric measurement points per
AHRAE Fundamentals
Amplified Velocity Pressure
Pv amplified 230 to 290%
Averaged Pressure Output
Center averaging on all units
Abated Noise & Pressure Drop
Precision-machined aircraft grade aluminum
tubes
THE PREMIER AIR FLOW SENSOR
IN THE VAV INDUSTRY
HomeFactory Integrated Johnson Controls DDC Controls
Provides a single source of responsibility for the
successful operation of the VAV system – no finger
pointing!
Boxes arrive with software installed, and are under
control as soon as they are powered up.
Allows the controls team to easily integrate the
controller and it’s application in the factory.
With our VMA controllers, the balancer does not need
to climb a ladder – all readings can be taken at the
zone sensor.
VMA 1610 BACNET CONTROLLER
Scheduling VAV boxes and controls together:
HomeGoing Further With Wireless
Put the zone sensor anywhere you want
– as long as it can “see” any other
device on the system, you are
connected.
Units delivered with factory integrated
wireless can be operational as soon as
power is connected.
Reduced controls installation cost –
controls technicians do not need to
reach the boxes.
Boxes can be moved during
construction or in the future without
worrying about the cabling to the sensor
When you specify wireless BACnet controllers using the ZigbeeTM
standard:
HomeVAV Terminals
Superior & Certified Performance
FlowStar™ airflow sensor
ARI 880 certified sound performance.
ARI 410 certified coil performance
ETL certified Electronic controls installed within a NEMA 1 enclosure
Composite shaft to eliminate condensate formation in the control box.
Unique design wraps the insulation edges without the need for metal
nosing.
Self-lubricating bearings reduce friction and air leakage
3 speed motors with SCR for precise and safe control of low air flows.
Model TSS, Outlet View
TCS Series Flow
Constant Volume
Fan Powered 100-4800 CFM
TVS Parallel Flow
Variable Volume
Fan Powered 100-4100 CFM
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Proper airflow over elements regardless of
damper position.
Eliminates nuisance contactor cycling.
Prolonged element life.
Reduces temperature stratification.
Allows lower minimum CFM setpoint.
cETL listed as an assembly.
Fully modulating heat with absolutely silent
SSR controls.
Single point power connection for ease of
installation.
Heater Elements Located UPSTREAM of Valve
Single Duct Terminal With Electric Heat
(Heater
Removed)
HomeSingle Duct Terminal
Design Flexibility
Air flows from 100 to 8,000 CFM
Water coils up to 4 rows for cold climates and low water
temperature applications.
Steam coils
Factory integrated controls for BACnet, N2, and LON
Integral sound attenuators for very sound-sensitive applications.
Access doors to allow easy coil cleaning.
LEED-compliant packaging
Global design – the same units are available throughout the world.
Model TSS
HomeFan Powered Terminals
Design Flexibility – everything available on the
single duct PLUS:
Small footprint, and only 14” tall to 1,000 CFM, and only 17”
tall to 2,300 CFM.
Available ECMTM motor for increased energy savings.
Can operate at up to 0.8” external static pressure.
Integral sound attenuators for very sound-sensitive
applications.
Second inlet and control for ducted outside air available.
Silent relays for staged electric heat (modulated heat is
always silent).
Dual point power to support emergency applications
available.
Global design – the same units are available throughout the
world.
TCS Series Flow
Constant Volume
Fan Powered 100-4800 CFM
TVS Parallel Flow
Variable Volume
Primary 100-4100 CFM
Fan up to 2,400 CFM