VAV-SVX07F-EN 63
Troubleshooting
– Override damper open until CFM is above enabled flow setpoint fan will cycle OFF.
• If the UC400 controller is calling for the fan to be ON (viewed in the Status screen), and it is not,
then check the TRIAC output wiring and relay output
– Check BO4 to common
. It should have 24 Vac. If it does not, measure the power input to
on XFMR 24 Vac input and of the UC400 controller. The supply voltage should be
between 20.4 and 27.6 Vac (24 Vac cataloged). However, voltages at either
extreme may
result in system instability.
– TRIACs can be checked by purchasing a 24 Vac LED. Conne
ct LED wires to triac outputs on
controller. Raise setpoint to initiate call for heat. If the UC400 BO LEDs are lit, but the test LED
does not, replace the controller.
Note: Me
asuring the output voltage with a meter is not
a reliable test for TRIAC output
voltage. The TRIAC output requires a small amount of current draw in order to fully
switch 24 Vac to ground. The LED provides the required current draw.
– Remove fan wires from the UC400 controller and apply 24 Vac
directly to fan relay wires.
– Fan relay should energize. If it does not energize, check wi
ring. If the wiring check is good,
replace fan relay.
NOTICE:
Equipment Damage!
The UC400 controller outputs are switched to ground. Do not jumper 24 Vac to binary output
TRIAC(s) because damage will occur.
• After all checks have been completed, check motor fan winding integrity and bearing failure.
PSC (Permanent Split Capacitor) Variable Speed Motor Check
WARNING
Live Electrical Components!
During installation, testing, servicing and troubleshooting of this product, it may be necessary
to work with live electrical components. Have a qualified licensed electrician or other
individual who has been properly trained in handling live electrical components perform these
tasks. Failure to follow all electrical safety precautions when exposed to live electrical
components could result in death or serious injury.
If the PSC Variable speed motor co
ntrol d
oes not change the motor speed, check the following:
• Wires connected improperly. Refer to the section, “Appendix: Typical Trane Factory Wiring
Diagrams,” p. 68.
• Check voltage selection switch on si
de of varia
ble speed motor control. It should be set for
motor voltage.
• Check speed control by:
– Turning the voltage selection switch fully counterclockwise.
– Turning the motor speed control potentiometer fully
counterclockwise.
– E
nsuring the motor remains OFF.
• Turn voltage selection switch
fully clockwise, but:
– The m
otor speed control potentiometer still remains fully counterclockwise.
– M
easure the motor voltage. It should be no more th
an 8 Vac lower than line voltage.
– The voltage selection switch still remains full
y clockwise.
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