VAV-SVN03A-EN
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Central Control Panel
The VariTrac Central Control Panel is the central source of communications
and decision making between the individual zones and the air conditioning
unit. Connections to the CCP are:
• 24 Vac power
• binary inputs for an occupied/unoccupied signal and external priority
shutdown signal (optional)
• ICS communication bus to the building automation system (optional)
• UCM communication bus to the VAV boxes and Trane Voyager commercial
27 ½ - 50 ton VAV rooftop unit
Unit Control Module (UCM)
A unit control module is mounted to each individual VAV terminal unit.
Inputs and outputs consist of the twisted shielded pair communication link,
zone temperature sensor, optional CO
2
and occupancy sensors, 24 Vac
power, damper motor control, and local heat outputs. Local heat may be
duct or space mounted, and can be staged electric, pulse-width modulating
electric, and modulating or staged two-position hot water.
VariTrane VAV Terminal Units
The function of the VariTrane terminal unit in a VAV control zone is to vary
the volumetric airflow rate to the zone. VariTrane units are supplied with
microprocessor-based DDC controls. Factory-installed controls are required
with all types of terminal units.
VariTrane VAV Terminal Unit Types
Single Duct
Single duct terminal units control the volumetric flow of supply air to the
space to maintain the zone temperature at setpoint. These units are gener-
ally applied in cooling-only VAV zones that require no heat during occupied
hours. If local zone heat is necessary, it can be provided either remotely (for
example, perimeter heat) or by terminal reheat (either electric or hot water
coils).
Parallel Fan-Powered
Parallel fan-powered units are commonly used in VAV zones that require
some degree of heat during occupied hours when the primary supply air is
cool. The terminal unit fan is in parallel with the central unit fan; no primary
air from the central fan passes through the terminal unit fan. The terminal
unit fan draws air from the space return plenum.
Series Fan-Powered
Series fan-powered terminal units are used commonly in VAV zones that not
only require heat during occupied hours, but also desire constant air vol-
ume delivery. The terminal unit fan is in series with the central fan. Primary
air from the central fan always passes through the terminal unit fan.
Central Control Panel
