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Troubleshooting
Diagnostic Table
Use the Diagnostic Table
understand issue.
Table 13. Failure parameters and Comm. 4 UCM actions
Sensed Parameter
Zone Temperature
Thumbwheel Setpoint
Air Flow
Auxiliary Temperature
(a)
CO
(b)
Supply Air Temperature
(VariTrac
Bypass Damper mode)
(a)
Supply Air Pressure
(VariTrac Bypass
Damper mode)
(a) UCM 4.0 and above will not detect an open. Instead, it will report 258 ppm.
(b) New to UCM 4.2
UCM Failure Procedures
In the event that the UCM is not operating, properly inspect the following:
•
•
•
•
Important: For final step check program by downloading good program using Rover, see page
UCM Communication Loss Procedures
In the event that the UCM is not communicating properly inspect the following:
1. Incorrect supply voltage/No voltage
60
(Table 13, p.
Failure Criteria
Open OR Short (> 25 seconds) AND no active
wireless sensors.
Open OR short AND no active wireless sensors.
For UCM 3.3 and prior, Flow < 10% when flow
control point > 10% OR flow > 110% or 150% for
For UCM 4, Flow < 5% when flow control point >
10% OR flow > 115% or 155% for series C.
UCM 4 will also indicate open/short for the air flow
Open or short
Short or C0
Open or short
Open or short
Incorrect supply voltage/No voltage
The green LED indicates power and should be "steady" ON.
Measure the power input to TB1-1 (power) 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.
If no voltage, check up stream of controller to see were voltage has been interrupted. See
complete wiring diagrams,
48.
• The green LED indicates power and should be "steady" ON.
60) for failure parameters and Comm. 4 UCM actions to help
series C.
sensor.
value < 200 ppm
2
Figure 44
to
Figure
51.
Action Taken
If failed open, control valve as if very cold
temperature. If failed shorted, control as if very hot
temperature.
Setpoints from EEPROM used.
If unsuccessful at recovering flow signal, operate in
pressure dependent mode until flow signal
regained.
For UCM 4, if flow input is open or shorted the flow
failure flag will be set and pressure dependent mode
will be used.
UCM 3.3 is the only version that sets the failure flag
if the valve is flowing too much air (>110% or 150%
for series C)
Tracer supplied data used for auto changeover logic.
For UCM 4 with the aux input configured for C0
mode: if the C0
input is shorted or reading below
2
200 ppm, the Failed C0
sensor failure flag will be
2
set.
For UCM 4 in bypass damper mode: if the SAT input
is shorted or open, the Failed SAT sensor failure flag
will be set.
For UCM 4 in bypass damper mode: if the SAP input
is shorted or open, the Failed SAP sensor failure flag
will be set.
2
VAV-SVX01C-EN
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