Heat Ramp Used On The Revised C-Trac2.1; Hot Water And Steam Heating; Simulate A Call For Maximum Heat; Economizer Control - EngA C-TRAC2 Installation, Operation And Maintenance Manual

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Heat Ramp Used on the Revised C-TRAC2.1

This revision was made to Model C-TRAC2.1 in the spring of 1996. It has a 0 to 10-volt heat output ramp to
modulate different heating controls (G-TRAC, G-TRAC2, DJM2.1, H-TRAC, etc.) The 0 to 10 VDC modulating
output signal comes from the C-TRAC2.1 new terminal "HD" (Positive) and the existing "B" terminal (negative).

Hot Water and Steam Heating

The heat output ramp can also be used to drive 2-way or 3-way mixing valves on hot water or steam coils on
air handling units. These can be reverse or direct acting depending on piping and wiring of the mixing valves.
Note that the output of the C-TRAC is not reverse acting. A resistor bridge network is required for actuators,
which drive the above valves. Actuators can be 3 wire or 2-wire type.

Simulate a Call for Maximum Heat

To simulate a call for maximum heat jump the discharge sensor connections Q and M and place the C-
TRAC2.1 dip switches in the following positions. If the C-TRAC2.1 is in any other mode than heat at the time
you perform this function, turn the power to the C-TRAC2.1 "off " for 10 seconds, then turn it back on. This will
enable a faster response, as you will not need to wait for as many internal mode time delays.
1
2
3
4
5
This has the C-TRAC2.1 operating strictly as a discharge air controller and the jumper forces the control to
call for full heat, as its sensor input is now always cold.
Pots that affect the heat control on the original C-TRAC are pots 3, 6, and 11. The proper settings depend on
the type of heating controller in use and the set point of the cooling deadband pot 3. Pot 6 does not exist on
the newer C-TRAC2.1 (it is a fixed value).
Pot 11 (on both original and new C-TRAC) is the heat envelope pot. It is set to suit the type of heat exchanger
and heat control being used.
(On the original C-TRAC, pot 6 is the heat offset pot. This acts similar to the Honeywell T872 room thermostat as it sets
up a deadband between the two levers. The C-TRAC pot 6 setting is from 5 to 0. When it's set at 5 there is very little
offset and when its at 0 the heat set-point is at its furthest below the cooling set-point [the set-point on the knob].)

Economizer Control

Many units today use multiple 0 – 10 VDC direct acting motors. Most of these do not require shunt resistors.
The original C-TRAC had one economizer signal. It operates Honeywell series 90 motors from the "R, B", and
"W" terminals on the C-TRAC and modulates the dampers by placing a slightly unbalanced voltage on the
damper motor terminals "R, B", and "W".
The C-TRAC2.1 has added a 0 to 10 VDC economizer ramp. This will usually be operating the newer direct
drive motors on the market today. There is a modulating output from terminals "ED" (positive) and "B"
(negative). Zero volts is minimum position, ten volts is full fresh air.
If the discharge temperature is too hot the C-TRAC2.1 will energize the economizer after passing through the
heating mode time delay. The length of time depends on the urgency of the overheating call. Typically this
delay will be from 4 to 10 minutes.
The damper motor is normally on its own ungrounded isolated transformer.
The C-TRAC2.1 will use the economizer as another device to maintain the calculated discharge temperature.

Minimum Pot Position

Pot 7 is the minimum position pot. When it is used it can be adjusted from 0 to 100% opening. The usual
setting is in the 10% area if no other set point is specified. Note that the minimum position pot on the C-
TRAC2.1 is not always in use. There are instances where a separate minimum position pot is being used. If a
separate minimum position pot is being used it is usually located in the damper motor and pot 7 should be left
at 0 position.
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C-TRAC2.1 MANUAL
March 1999 R1