110
Rooftop Dedicated Outdoor
Air System Installation Manual
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Table 70: Troubleshooting Controls Table, continued.
Controls Symptom
Probable Cause
Description
Outdoor air damper does
not open.
Occupancy.
The outdoor air damper is controlled closed during the unoccupied mode. On units with return
air, the return air damper is controlled open (recirculation) in the unoccupied mode. Verify the
occupancy mode.
Morning warmup and
cooldown.
On units equipped with this feature and return air dampers, the outdoor air damper may
close and the return air damper may open for up to 30 minutes upon entering occupied
operation. Check the Morning Warmup page of the handheld LCD.
Energy recovery wheel
failure.
On units equipped with return air dampers, energy recovery wheels, and energy recovery
rotation sensors, the outdoor air damper may close and the return air damper may open to
raise (heating) or lower (cooling) discharge temperature. This only occurs if heating / cooling
capacity is insufficient and the energy recovery wheel rotation sensor does not detect motion.
End switch failure.
When the outdoor air damper is commanded open, the controller waits for the end switch of
the damper actuator(s) to confirm that there is an airflow path. If, after two (2) minutes, end
switch closure is not confirmed, a damper switch (end switch) alarm is generated. It must
be manually reset from the handheld LCD. Check the damper actuators are properly
configured. Set Mode dial = 3. If actuator is equipped, set outdoor air damper AUC dial = 0.25
and return air damper AUX = 0.75.
Dehumidification not
enabled.
Space relative humidity
sensor / value.
Occupied dehumidification is enabled when the space relative humidity or outdoor dewpoint
temperature is greater than setpoint. If the space relative humidity sensor is not connected or
operating properly, dehumidification will be determined by the outdoor air dewpoint. The space
relative humidity reading may be sent by the BAS.
Outdoor air dewpoint
setpoint.
Occupied dehumidification is enabled when the space relative humidity or outdoor dewpoint
temperature is greater than setpoint. The outdoor dewpoint is calculated from the outdoor air
temperature and relative humidity. If either the outdoor air temperature or relative humidity
sensor is not connected or operating properly, dehumidification may not operate. The outdoor
air temperature and relative humidity may be sent by the BAS.
Space dewpoint
dehumidification cutout.
Dehumidification of the space is disabled when the space dewpoint falls below this threshold
Check the space temperature and relative humidity sensors for proper operation. Space
temperature and relative humidity reading may be sent by the BAS.
Unoccupied space
dewpoint setpoint.
Unoccupied dehumidification is enabled when the space humidity is greater than setpoint.
Check the space relative humidity sensors. The space relative humidity reading may be sent
by the BAS.
Gas furnace does not
operate.
Electric heat inter-stage
delay.
For units with both gas and electric heat (Temperator option), the electric heat is the first stage
of heat, followed by gas heat. For gas heat operation to be enabled, the electric heat
must be at 100% capacity for five (5) minutes.
High limit output.
Both gas and electric heaters are equipped with high temperature limit switches, both manua
and automatic reset. Check schematics for locations and operation type.
Occupied / unoccupied
control not operating
properly.
Local (internal)
schedule.
Unit default is 24 / 7 occupied by internal schedule, which is edited using the Schedule menu
of the handheld LCD. Be sure to set the controller time and date.
Hardwired occupancy
input.
To allow hardwired input to determine occupancy set local schedule to 24/7 unoccupied.
Input U15 on the DDC1 must have continuity with input 0V closed contact) for occupied
operation. When input U15 is open, the unit is unoccupied.
Controller time and
date.
The local time and date must be set for the local schedule to correctly determine the
occupancy mode. These values are stored in the controller for several months with battery
backup. Use the System Settings menu of the handheld LCD.
Network (BAS)
schedule / command.
The two occupancy points are BAS occupancy enable and BAS occupancy command. When
BAS control of occupancy is enabled, the BAS occupancy command point determines
occupancy. Check the BMS Interface page of the handheld LCD to see the status of these
points.
Compressor does not
cycle off.
Coil temperature
setpoint not satisfied.
In the dehumidification mode the compressors cycle to maintain the evaporator coil
temperature setpoint (53°F, typical). At least one compressor will remain on while
dehumidification is active.
Supply air temperature
setpoint not satisfied.
During the normal control sequence (dehumidification not enabled) the compressors cycle to
maintain the supply air temperature setpoint. The compressor(s) will remain on until the
supply air setpoint is satisfied.
TROUBLESHOOTING