74 VAV-SVX01C-EN
Troubleshooting
3. Tracer Summit has the fan output disabled
• Check group, global, and/or Tracer overrides to make sure they are not inhibiting fan
operation.
4. A flow override exists locking out the fan output
• Check to make sure Tracer or Rover has released fan disable override.
Note: If fan cycling is based on temperature go to step 5 and if it is based on flow go to step 6.
5. If fan control is based on temperature and Zone temperature is at or above the heating set point
plus heating offset on units configured as temperature control. A factory set differential of 0.5°F
(0.3°C) exists to prevent short cycling.
• Increase the UCM heating set point causing fan to be cycled on.
• Lower the Heating setpoint by .6° and the fan should cycle off.
6. If the fan control is based on flow, the unit fan will be energized whenever primary airflow is
below this set point. For this parallel fan configuration, the fan control point, if specified in a
percentage of unit airflow, must be set between 15% and 30% of the units cataloged airflow to
assure proper operation. A differential of 5% exists to avoid excessive fan cycling.
• Override damper closed until CFM is below enabled flow setpoint
• See if fan cycles on
• Override damper open until CFM is above enabled flow setpoint fan should cycle off
7. If VAV UCM is calling in the status menu for the Fan to be on and it is not then check UCM Triac
output, wiring, and Relay output.
• Check J8 to TB1-2. Should have 24 VAC; if it does not if not 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.
• Triac can be checked with purchasing a 24 VAC LED and see if it lights up on call for fan UCM
if LED does not light up replace UCM.
• Remove fan wires from UCM and apply 24 VAC directly.
Figure 42.
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