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EMS Wiring
The RS-485 communication cable to the C-TRAC3 is 24awg shielded twisted pair (STP) with a shunt
capacitance of 16pF per foot and 100 ohm characteristic impedance. Category 5 cable can be used as
defined by the EIA/TIA/ANSI 568 specification.
TROUBLE SHOOTING
The C-TRAC3 is designed to simplify service and troubleshooting. Most equipment failures and problems
occur due to sources external to the C-TRAC3, and can easily be traced with a digital multimeter.
Advanced troubleshooting may require the use of a computer.
BASIC (MULTIMETER)
The equipment has a function and terminal list attached to the electrical panel door. These explain how
the equipment is designed to operate. This information, along with the flashing patterns from the C-TRAC3
status lights and multimeter sensor and setpoint readings should allow for a majority of troubleshooting to
effectively take place.
Do not jumper or open circuit sensors. If necessary it is possible to substitute fixed or variable resistors in
place of the sensors for test purposes. Refer to the table later in this document for various sensor values at
various temperatures.
There is a test point and DIP switch block near the RS-232 connection for checking actual temperatures
and setpoints. Refer to the DIP switch settings to determine which of the 4 possible variables are being
read. Referenced to ground, measure a DC voltage that relates to temperature in °C. Refer to Table 3 and
Table 4 below.
Vdc
0.5
°C
5
°F
40
Note the above actual temperature reading is the value at the Engineered Air sensor or setpoint. If there is
a building management system measuring temperature, its sensor should be located within one inch of
the Engineered Air sensor.
DIP Switches (C-TRAC 3.2 and higher)
A DIP switch block located to the left of the RS-232 connector will switch the multimeter test point to read
a variety of temperatures and setpoints. See the table below. Note that early versions of the
C-TRAC3 had selection jumpers.
1.0
1.3
1.5
10
13
15
50
55
60
15 of 21
Table 3
1.8
2.1
2.4
18
21
24
65
70
75
C-TRAC3
2.7
2.9
3.2
27
29
32
80
85
90
Jan 13 R5
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