Overview; Bacnet Protocol; Bacnet Testing Laboratory (Btl) Certification - Trane Tracer Uc

Overview

The Tracer™ UC400 controller is a programmable, general-purpose BACnet®, microprocessor-
based, direct digital controller (DDC). This controller can be installed as a factory or field device.
When this controller is factory installed on Trane™ variable-air-volume (VAV) terminal units, the
factory downloads the unit with the appropriate VAV programs and configuration settings for the
unit. These can include sales-order-specified airflow setpoints.
Trane VAV units are made with either pneumatic or microprocessor controls (DDC/VAV). This
manual considers only terminal units with BACnet UC400 controller DDC/VAV controls. Factory-
installed DDC/VAV controls are available with all single duct terminal units, parallel fan-powered,
and series fan-powered units.
The UC400 controller can be configured with three (3) different application programs:
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BACnet Protocol

The Building Automation and Control Network (BACnet and ANSI/ASHRAE Standard 135-2004)
protocol is a standard that allows building automation systems or components from different
manufacturers to share information and control functions. BACnet provides building owners the
capability to connect various types of building control systems or subsystems together for many
uses. In addition, multiple vendors can use this protocol to share information for monitoring and
supervisory control between systems and devices in a multi-vendor interconnected system.
The BACnet protocol identifies standard objects (data points) called BACnet objects. Each object
has a defined list of properties that provide information about that object. BACnet also defines a
number of standard application services that are used to access data and manipulate these objects
and provides a client/server communication between devices.

BACnet Testing Laboratory (BTL) Certification

The UC400 supports the BACnet communication protocol and has been designed to meet the
requirements of the application-specific control profile. For more details, refer to the BTL web site
at www.bacnetassociation.org.
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Space Temperature Control (STC)
When the UC400 controller is configured for STC, it modulates the VAV damper blade based
on the zone temperature, measured airflow, airflow and temperature, and setpoints, to
continuously control conditioned air delivery to the space. The volume of monitored incoming
air and the damper adjusts to provide accurate airflow control independent of the duct
pressure. The damper modulates discharge airflow into the space between operator airflow
setpoints depending on space conditions. Additionally, the fan and heat outputs may be
energized depending on the application.
Ventilation Flow Control (VFC)
When the UC400 controller is configured for VFC, it can be applied to a VAV terminal and used
to temper cold outdoor air that is brought into a building for ventilation purposes. The tempered
air is intended to supply an air handler unit (AHU), which provides comfort control to the zones
it is serving. The VAV terminal supplies the correct amount of ventilation air. When reheat is
added, it tempers the ventilation air to reduce the load on the air handler by sensing the
discharge air temperature of the VAV unit, and controls its long-term average to the discharge
air temperature setpoint.
Note: Communicated Discharge Air Temperature Setpoint range is between 19°F and 70°F .
Flow Tracking Control (FTC)
When the UC400 controller is configured for FTC, it works in conjunction with another UC400
configured for STC. The current discharge airflow from the STC controller is communicated to
the FTC controller. The FTC controller is then configured to supply a offset (positive or negative)
flow relative to the of the other VAV box(es). This is used to provide positive or negative
pressure to a contain zone.
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