Table of Contents
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Chapter Overview
This chapter contains the trouble
analysis for UCM 4.0 problems,
wireless receiver problems, and
provides answers to frequently asked
questions pertaining to wireless
receivers.
38
Trouble
Analysis
CHAPTER 8: TROUBLE-SHOOTING
UCM 4.0 Problems
In the event that the UCM does
not communicate, properly
inspect the following:
1. Incorrect supply voltage
— The green LED indicates power and
should be "steady" ON.
— Measure the power input to TB1-1
(common) and TB1-2 (ground) of the
UCM board. The supply voltage should
be between 20 and 28 VAC (24 VAC
cataloged). However, voltages at either
extreme may result in system
instability.
2. Communication link polarity is
reserved.
— The yellow LED will be ON indicating a
reversed polarity. Switch the
communication link connection.
3. UCM is not addressed correctly
— Verify the DIP switch settings on the
UCM.
4. Communication link signal has
interference
— Communication link should not be
routed near or with any voltage source.
5. Incorrect wire used
— Recommended wire is twisted shielded
pair. See Chapter 2 for the wiring
specifications for the UCM.
6. Defective UCM board
— Be sure all other recommended actions
listed above have been taken.
Disconnect the communication link
from the board and check the board's
ability to communicate with the Trane
EveryWare Software. If
communications do not exist, the
board is assumed defective.
In the event that the UCM will not
display data, properly inspect the
following:
1. UCM not correctly addressed or two
UCM's addressed the same
— Check the DIP switches on the first VAV
box and remove the communication
link from the second VAV box.
2. Communication wiring error (shorts,
open, or reversed polarity)
— Remove the communication link past
the first VAV box and verify the polarity.
Check resistance across the
communication wires for possible
shorts or open circuitry.
3. UCM has no power
— Check the green power LED and check
the 24 volts AC supply at TB1 on the
UCM board. Voltage should be between
20 volts AC and 28 volts AC (24 VAC
cataloged). However, voltages at either
extreme may result in system
instability.
4. Failed UCM on the communication link
— One UCM failure can bring down all
UCM communications.
In the event that the UCM reports
an incorrect zone temperature or
set point, properly inspect the
following:
1. Zone sensor wired incorrectly
— Check wiring for the correct
connections. See Chapter 2 for further
details on zone sensor wiring.
2. Defective zone sensor
— Disconnect the zone sensor terminal
plug from the UCM and using an
Ohmmeter, measure the resistance
across the plug terminals TB3-1 and
TB3-2 for the set point. Compare the
resistance to temperature using Table 8
in Chapter 5.
— Additionally, measure these values at
terminals 2 and 3 on the zone sensor.
These values should be near those
measured above. If not, the connecting
wire is faulty.
In the event that the zone sensor is
reading incorrectly, properly inspect the
following:
1. Zone sensors open or shorted out
— Check the resistance across the wires
at the UCM and compare the resistance
to the values shown in Table 8.
2. Actual room temperature is higher or
lower than what the UCM reads
— Check the location and installation of
the zone sensor. Change the calibration
factor in the UCM setup screens.
VAV-SVX01B-EN
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