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completely shut down, turn the main disconnect switch off prior to attempting any service or
maintenance.
Additional details regarding startup and shutdown are noted in the unit function and in the Installation,
Operation and Maintenance manual.
TEMPERATURE CONTROL
BASE SETPOINT
The C-TRAC3 is designed to be a discharge air temperature controller. The base discharge air temperature
setpoint is typically set from the setpoint 1 control knob located on the face of the
C-TRAC3. Optionally, this setpoint may be replaced by a remote mounted potentiometer, directly set from
a remote BMS signal (0-10Vdc), preset from a computer, or commanded from an EMS signal. If not used,
set this knob to maximum (fully clockwise), as noted on the face of the C-TRAC3.
The C-TRAC3 has the ability to perform 2 independent operations at the same time, such as a
dehumidification system (pre-cool and reheat) or a multizone system (hot deck, and cold deck). These
types of systems normally incorporate both face-mounted setpoint dials, but the optional setpoints noted
above can still apply to both or either setpoint. As above, if setpoint 2 is not used, set to maximum, as
indicated on the face of the C-TRAC3.
SETPOINT RESET
The base discharge air temperature is normally modified from a remote signal to maintain the desired
temperature of the supplied space. This is called reset. The C-TRAC3 discharge temperature can be reset
from a variety of sources such as ambient air temperature, modulating or staged room thermostats, return
air temperature, or a BMS signal (0-10Vdc).
The resulting change in the discharge temperature setpoint from reset is the actual, or calculated,
discharge air temperature setpoint. This is normally referred to as the SPC.
SETPOINT LIMITS
The discharge air setpoint range is set, and limited to, a specified temperature range programmed prior to
shipment. For example, if the minimum discharge temperature is programmed at 60°F, then that is the
minimum possible temperature setting. Even though the setpoint dial may go as low as 50°F, the
calculated, or actual, setpoint can never go below 60°F.
MODES OF OPERATION
The C-TRAC3 has 3 distinct sequential modes of operation: heating, economizer and cooling. Depending
on ambient conditions the C-TRAC3 may start in any of the three modes. Mode change time is five
minutes (six minutes from heat to mechanical cooling if there is no economizer). If the C-TRAC3 is unable
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C-TRAC3
Jan 13 R5
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