| Application Considerations Figure A-16 - Traq Damper Mixing
Box Module -- Inlet Duct Requirements
AHU Compoents
Modular Climate Changer® air handlers adopt a
"building-block" approach to air handler
design. Each "building block" or module
contains one or more components that serve a specific
purpose unique to each application. The air-handling functions needed, along with
the desired layout and arrangement, ultimately
determine what modules the air handler must include.
The rest of this section briefly summarizes the general purpose and application
considerations (if any) associated with each MCC module
type. Make sure the selected modules and final air handler design diligently address
indoor air quality and compliance with ASHRAE Standard
62- 1989 in a manner that optimizes the unit’s footprint, performance and acoustical characteristics. Also bear in mind
that a factory-packaged air handling system with
integral controls is typically more efficient, more
cost- effective and less prone to misapplication than a comparable "built-up"
system.
Intake Module
As its name implies, this module provides a means for outdoor air to enter the
air handler. A screen on the intake opening prevents
birds from entering the air handler, excluding them as a potential source of bioaerosol
contaminants. The module also contains a moisture
eliminator and a drain pan to remove water (rain) from
the outdoor air stream as it enters the air handler.
Moisture Eliminator Module
Used to remove rain or entrained water from the passing air stream, this module
is typically used with a mixing box or economizer
module in lieu of an intake module. It may also be used
immediately downstream of a cooling coil module in single-zone blow-thru arrangements
(not required with plug- type fan modules and not
available on Q-fan modules because blow-thru coil
applications are not recommended) to prevent moisture carryover.
Mixing Box Module
The mixing box module typically combines the incoming outdoor air with
recirculated return air collected from the occupied
space, and is commonly included in an air
handler’s design to control the mixture of outdoor and recirculated return airflow. Freeze protection for coils downstream of
mixing box should be used when incoming outdoor air is
below 35 F. See "Protecting Hydronic Coils from
Freezing" on page 13. When equipped with an optional Traq damper assembly,
the mixing box module permits direct measurement of
outdoor airflow to assure compliance with ASHRAE Standard 62-1989.
Traq™ Damper Option.
Designed to measure and
modulate outdoor airflow, the Traq damper assembly
consists of one to six butterfly-type dampers. Each damper’s bell-mouth inlet guides air uniformly through a flow-sensing
ring that accurately measures total and static pressure
from 15- to 100-percent of nominal flow. The damper assembly’s ventilation control module (VCM) produces a 2-to-10-VDC signal
proportional to airflow, recalibrates itself once every
60 seconds, and automatically adjusts for temperature variations.
Application considerations:
- The Traq damper mixing box requires only one duct diameter of straight inlet duct (i.e., as much as 80 percent less than
other airflow-monitoring techniques); see Figure A-16.
- Connecting a Traq-equipped air handler to a building automation system such as a Tracer® building management system
permits: (a) dynamic calculation of the outdoor air
needed to adequately ventilate a multispace VAV system
and reset the outdoor air set point accordingly to save energy; and (b) trend logs and custom reports to document
compliance with ASHRAE Standard 62.
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