Greenheck EHV-602 User Manual

Indoor Air Quality

Air Flow Measuring Control Damper

IAQ-42

April

2006

Why is outside air measurement important?

There are many signifi cant benefi ts to monitoring outside air volumes. First, by measuring the amount of
outside air coming into a building you can be assured that the building is complying with all applicable
indoor air quality codes including ASHRAE Standard 62 and California Title 24. Meeting these minimum
requirements reduces indoor airborne viruses and bacteria which can lead to Sick Building Syndrome.
Studies have shown that buildings that are under ventilated suffer from reduced productivity levels.

The second major advantage to monitoring outside air volumes is that it eliminates costly over ventilation. In
addition to increased energy costs associated with heating and cooling of outside air, over ventilation causes
in an increase in humidity that can result in mold development.

Where should an air measuring damper be used?

Exhaust Air

Mixed Air

Outside Air

Exhaust Air

In this application an air measuring control damper is used to measure and control outdoor air intake while a
second air measuring control damper is used to measure and control the exhaust fl ow. The set point for the
exhaust air damper would track the fl ow of the outdoor air damper (minus a differential if positive building
pressure is desired.)

Mixed Air

In this application, an air measuring control damper is used to measure and control outdoor air intake while
a second air measuring control damper is used to control the mixed air temperature. Normally an averaging
sensor is required for mixed-air temperature control because the large temperature differences between
return air and outdoor air cause stratifi cation. The mixed air temperature is calculated from the fl ows and
temperatures measured by each damper eliminating the measurement problem caused by stratifi cation.

Outside Air

In this application, an air measuring control damper provides outdoor air control based on a demand signal.
The demand signal could be determined by a set schedule or by occupancy sensors. Examples of demand
signals are carbon dioxide (CO2) concentration, a binary signal from a motion detector, or a manual switch.