VAV-SVX03A-EN
17
System Check
Improper room control may be caused
by areas other than the VAV boxes.
Before replacing the air damper or
control box, make sure that the entire
system is operating properly and is
supplying sufficient air to the damper.
Complete the following checks.
1. Look for obvious leaks in the duct
system. Assure that sufficient static
pressure is present at the air
Damper.
2. Inspect the supply fan and VAV fan
filters. Clean or replace, if necessary.
3. Check zone sensor location, outside
wall, appliances, direct sunlight or the
supply air stream may be artificially
heating or cooling the zone sensor.
4. Evaluate diffuser should have 15" of
flat ceiling surface on either side of the
slot to assure proper air distribution.
Check that airflow from grills or
diffusers is properly balanced.
5. For accurate flow control, there must
be at least two duct diameters of
straight ductwork before the air
damper inlet. Electric coils require four
feet of straight ductwork downstream
of the coil.
6. Compare voltage requirements, as
specified on the side of unit with actual
voltage supplied to the unit. The
control voltage requirement is
24-volts AC + 10%.
Troubleshooting
Air Damper and Motor Check
If problems occur with damper actua-
tion, perform the following steps:
1. Visually inspect the damper for loose
gaskets, casing damage, or restriction
to damper travel.
2. Be sure that there is proper voltage
supplied by checking for 24 volts at
terminal 1 and 2 on the circuit board.
Acceptable voltage range is 21.6 to
26.4-volts AC.
3. To open the damper, apply 24-volts AC
to the white and green wires on the
motor plug coming from the actuator.
The drive takes a maximum of 90
seconds to fully open.
4. To close the damper, apply 24-volts AC
to the white and red wires on the
motor plug coming from the actuator.
5. If the motor fails to operate from a
direct 24-volts AC power source, and
there is neither binding nor
obstructions, then the actuator is
defective and should be replaced.
Control Check
Zone Sensor Check
To troubleshoot the zone sensor, make
sure that 24 volts are available at the
control unit board and then complete
the following procedure:
1. Move the zone sensor to full cooling.
The damper should open completely.
If the action is reverse, check the
proper zone sensor connection.
2. Rotate the zone sensor knob to full
heat. This should cause the damper to
close and fan to come on. When the
room setpoint is above the actual
room temperature, stages of heat will
be energized, if enabled.
3. If the zone sensor does not operate at
all, check the wiring from the board to
the sensor. Reference the zone
sensor section.
4. Check DC voltage at zone sensor
terminals 2 and 3 (6-volts DC). Turn
the zone sensor to full heating voltage;
it should be equal to or less than
5.4-volts DC. Turn the zone sensor to
full cooling; voltage should be equal to
or greater than 6.5-volts DC.
Heater Contactor Check
To troubleshoot heater contacts on units
with electric reheat, complete the
following procedure:
1. Disconnect power source.
Hazardous Voltage!
Certain tests or calibration procedures
described in this section may involve
working in close proximity to live
electrical terminals. Only qualified and
licensed electrician or other properly
trained in electrical safety when
working with live voltage should
perform these procedures. Failure to
follow all electrical safety precautions
when exposed to live terminal could
result in death or serious injury.
WARNING
WARNING
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
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
1. Disconnect power source and remove
zone sensor wires 3, 4, and 5. Be sure
to mark the wires so that they will be
correctly replaced.
2. Reconnect power to the unit. The
damper should move to its minimum
or fully closed position.
3. Jumper terminals 4 and 5. The green
LED should light. This should cause the
damper to move fully open or to its
maximum flow setting.
4. Disconnect the jumper from terminals
4 and 5.
5. Jumper terminals 3 and 4. The amber
LED should light. The damper should
close to minimum and the relays (or
reheat) should energize.
6. Remove Jumper terminals 3 and 4.
7. If everything operates correctly,
disconnect power and reconnect all
wires. Check the air damper or zone
sensor for further trouble analysis.
2. Disconnect wires from the contactor.
3. Connect an ohmmeter to the contacts.
4. Apply 24 volts (from independent
power supply) to the coil of relays.
Check for contact closure. If the
contact does not close, replace
the contactors.
