HVAC Control Strategy

Pressure Dependent Volume Control

MW

Pressure Independent Volume Control

Δp

V

M

W

Pressure Independent Volume Control

DpV

t

DpV

t

Dpv

+

Dpv

+

Pressure Air Flow

V

Air Flow Measurement

Flow Characteristics

D6l .min =D

Round Duct

Rectangular ductπ

whl

4.2

min=

Dl ⋅= 2min

Honey-Comb Air flow Straightener

With Honey-Comb Air Flow Straightener We get,

!

• Drastically Reduced Straight Length required for Accurate & Reliable Air Flow Measurement.

!

• Accurate & Reliable Air Flow Measurement, even at non ducted application such as outdoor air intakes.

Without Air Flow

Straightener

With Air Flow

Straightener

Non Linear Calibration

Healthy buildings at reduced energy cost.

Why Optimal Ventilation is Critical?

• Under Ventilated buildings suffer from reduced productivity levels. • Over Ventilated Buildings result in increased humidity levels. • Ventilation rates also have a direct bearing on energy costs !!• Demand Controlled Ventilation, or DCV

– Reduces indoor airborne viruses and bacteria which can led to ‘Sick Building Syndrome’.

– Reduce the cost of operating the HVAC system.

Traditional Approach

Use of pressure dependent volume control

Traditional Approach

In Multiple Space using one CO2 sensor

How Optimal Ventilation Can be Achieved?

• First and foremost is to measure the amount of outdoor air coming into a building.

!

• And then, Reset intake air flow (Demand Controlled Ventilation) in response to variations in zone population and ventilation efficiency both.

Demand Controlled Ventilation – Various Methods

• Reset based on occupancy – Occupancy Schedule

• Predicts the current population based on the time of day – Occupancy sensor

• It detects the number of people in each monitored zone – CO2 Sensor (Most Effective)

• Monitors the concentration of CO2 produced !• Reset based on ventilation efficiency

– Reset Intake air flow in response ventilation efficiency Variation

DCV - CO2 Based

DCV – SINGLE ZONE

DCV - Single Zone CO2 based

DCV - Single Zone CO2 based

DCV - MULTIPLE ZONE● CO2 Based DCV alone ● Ventilation Reset alone ● Ventilation Reset Plus

CO2 based DCV

ASHRAE Standard 62.1-2007-Multiple Space Equation 6-1

ASHRAE Standard 62.1-2007-Multiple Space Equation 6-1

ASHRAE Standard 62.1-2007-Multiple Space Equation 6-1

CO2 Based DCV Alone

CO2 Based DCV Alone

Ventilation Reset

CO2 Based DCV with Ventilation Reset

VAQ Station

An Effective Solution for Pressure Independent Volume Control

VAQ Station-Selection Chart

VAQ Station-Earn valuable LEED Credits

Questions?