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.