EngA C-TRAC2

A C-TRAC2.1 MANUAL
IOM-12 Page 5 March 1999 R1
IX. STATUS LIGHTS
The C-TRAC2.1 has 4 status lights.
Heating Control Mode
This light is on whenever the C-TRAC is in the heat mode (the C-TRAC2.1 always starts in heat mode).
Cooling Control Mode
This light is on whenever the C-TRAC is in mechanical cooling mode.
NOTE: If neither the heat nor cool light is on, the C-TRAC is in economizer mode.
Compressor Ambient Closed
This light is on whenever an externally mounted ambient control places 24 VAC on terminal “A”.
Internal Timer
If this light is off when the C-TRAC was power, the control is satisfied and the C-TRAC calculated set point
and discharge temperatures are very close to each other. If it is on, the error between calculated set point and
discharge temperature sensor is such that the control is timing to either change mode or increase/decrease
the heat/economizer/mechanical cooling output.
X. FAN CONTROL AND LOW LIMIT
These functions are not controlled by the C-TRAC2.1. Other devices, external to the C-TRAC2.1, supervise
fan control and low limit.
XI. CONTROL START-UP AND OPERATING STRATEGIES
The C-TRAC2.1 will always try to satisfy the discharge temperature. If the C-TRAC2.1 is unable to satisfy the
discharge temperature in its current operating mode (heating, economizer or mechanical cooling) then it will
switch into the next operating mode. Depending as to how far the discharge temperature is from the
calculated desired discharge temperature determines how quickly the C-TRAC2.1 will switch to a different
operating mode or adjust the output in the mode it is presently in. There are three operating modes:
 Heating (heat light is on)
 Economizer (usually neither heat or cool light is on, the exception being constant economizer dipswitches 6 and 7
are off)
 Mechanical cooling (cool light is on)
NOTE: Remember the C-TRAC2.1 will always power up in the heating mode.
When the C-TRAC is in mechanical cooling mode and the compressors are in operation, if the ambient
control removes power from terminal A then the C-TRAC will go directly to heating mode. If there is no call for
heat and the calculated set point wants cooling, it will return to economizer mode in a few minutes, then
mechanical cooling.
Heat Output
The C-TRAC2.1 always powers up in the heat mode. There are two possible heat output ramps to wire to
depending on the application.
Heat Ramp Used on the Original C-TRAC
The heat output control voltage is across terminals HT and B. The voltage varies from 0 VDC for no heat call,
0.75 for low heat call, modulating through to 8.5 VDC for high heat call. Note that certain older controls
require a resistor network to reduce control voltage (such as the original DJM which, if not for the resistor network,
would be at high fire when there is greater then 4 VDC from the C-TRAC HT and B terminals).