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VAV-SVX03A-EN
Troubleshooting
Fan Motor Check
To troubleshoot the fan motor, complete
the following procedure:
1. Disconnect the power, check all wiring
diagrams provided on the unit.
2. Turn the power back on. Operate the
zone sensor to see if the proper
voltage is being supplied to the motor
relay. If the motor does not start, check
the capacitor and fan motor.
3. Check the motor relay by attaching a
voltmeter across the 24-volt coil of the
relay. For parallel fan-powered,
operate the zone sensor to energize
the fan and confirm the voltage to the
relay is turned on. Check for supply
voltage between the common and hot
side of the relay.
4. Attach a Voltmeter to the white
common wire on the terminal block
and the blue, black or red wires from
the fan motor. If line voltage is present,
check for fan obstruction.
5. With the power off, spin the fan wheel.
If it does not run freely, check shaft
alignment or housing clearances.
Circuit Board Check
1. Remove the control box cover. Inspect
all wiring and compare with the label
on the control box cover. The label
also indicates jumper connections.
Make sure that all wiring and jumpers
are connected exactly as shown on
the diagram.
2. Measure the voltage a terminals
TB1 –1 (+) and TB1 –2 (-) on the circuit
board. The voltage reading should be
24-volts AC +/- 10%.
3. Measure the voltage at terminal TB1-5
(+) and TB1-3 (-) on the circuit board.
Voltage reading should be 12-volts
DC + 10% tolerance. This voltage is
the output power for the zone sensor.
If these voltage readings are not
shown, it could indicate a
defective board.
4. If 12-volts DC is present, rotate the
zone sensor thumbwheel and check
for voltage change across zone sensor
terminals 2 and 3.
5. Adjust the minimum fully counter-
clockwise and the maximum
fully clockwise.
6. Verify the amber and green lights
change when rotating the
thumbwheel.
7. If any step does not work,
replacement of the board may be
necessary. If all steps work, proceed
with further component checks.
Transducer Check
1. Disconnect the tubing to the flow
sensor, remove the low-pressure line
first, then the high side. Transducer
damage may result if procedure is
not followed.
2. Attach the voltmeter to terminals TP4
(+) and ground, B1-2 or 3, or TP3.
Voltage on these terminals should be
between .1- to .4-volts DC; the ideal is
.254 volts DC.
Triac Output Check
1. Make sure that the zone sensor
operation is correct and, if applicable,
which zone sensor is under control.
Refer to prior sections for step-by-step
procedures.
2. Remove all connections from J9, J10,
and J11. In addition, remove J19 if it is
a series fan-power unit.
3. Set the zone sensor to the full
cooling position.
4. Place a 500-1000 ohm resistor
between the connectors J7 and J9
and measure the voltage between
these points. It should be less than 10
volts AC.
5. Slowly increase the zone sensor
setting from full cooling to heating. At a
position on the zone sensor near room
temperature, Triac #1, which connects
J7 to J9 should close. Next, Triac 2,
which connects J7 to J10, should
energize and finally Triac 3, which
connects J7 to J11, should energize.
When the zone sensor is rotated to the
full heating position, a voltage check
should show that contact closures
between J7 and J9, J7 and J10, and
J7 and J11 have been made (closed).
6. If continuity is not present at all stages,
replace the board.
Auto Dual Minimum Check
A digital voltmeter will be required to
make the voltage checks described in
this procedure. Note the following
differences in labeling of adjustment
potentiometer described in the follow-
ing steps:
Circuit
Board
Label
R8
Null Voltage Calibration
R67
Max Flow
R68
Min Flow A
R69
Min Flow B
1. Refer to calibration setup steps 1
through 4. Make changes as described
in the following steps:
2. Rotate the zone sensor to the full cool
position. The green LED should be
illuminated on the circuit board and
voltage present at terminals J1-3 to
J1-1. The voltage at terminal TP2 to
ground should be 5.9 volts DC
or higher.
Hazardous Voltage!
Disconnect all electric power, including
remote disconnects before servicing.
Follow proper lockout/tagout procedures
to ensure the power cannot be inadvert-
ently energized. Failure to disconnect
power before servicing could result in
death or serious injury.
WARNING
WARNING
3. Connect the voltmeter to terminals
TP1 (+) and ground. Voltage at these
terminals should be 4.78 to 4.82 volts
DC. If the voltage at these terminals is
lower or greater than the specified
tolerance, this could be the cause for
not obtaining correct minimum or
maximum flow. This causes the
controller to not operate within the
specified minimum and maximum
values, even with the minimum
potentiometer fully counter-clockwise.
Adjust R8 for 4.8 volts DC.
4. Reconnect the air valve actuator and
drive to maximum position. Voltage
should increase on TP4 to TP3.
5. If voltage does not increase, verify
with a magnehelic that the delta P
is increasing.
6. Replace the transducer if delta P
increases and voltage does
not change.
Note: A faulty transducer will cause the
air damper to function improperly.
