Trane Horizon OADG Series Installation, Operation And Maintenance Manual page 79

Space Control or Single Zone VAV and OA
Setpoints
Space Control or Single Zone VAV will no longer use the
outdoor air setpoints if the unit has an ERV, or if the unit is
not 100% outdoor air. Space conditions are used for
determining all modes of operation.
Discharge Air Temp. Reset for Single Zone
VAV
Single Zone VAV controls cooling and heating to constant
discharge air temperature, with the supply fan controlling
to space conditions. To reduce energy usage during
extremely low load days, the unit will reset the Discharge
Air Temperature Setpoint Active whenever the supply air
flow is within 10% of the minimum setpoint.
Supply Fan Tracking for Exhaust Fan (Field
Enabled)
VAV units can now have the exhaust fan track with the
supply air as it changes speed. The exhaust fan speed will
be 90% (adj.) of the supply fan speed.
Hot Water Reheat
Units with hot water installed will default from the factory
to use the hot water as reheat for chilled water, or
supplement hot gas reheat when it's at 100% capacity.
OAU-SVX006E-EN
Attention Startup or Service Technician
Expanded Fallback Control
Where possible, the unit will fall back to other methods of
control when it detects a failed sensor. A diagnostic is
displayed for the sensor when another sensor is being
used.
• Evaporator temperature sensor fail -> use suction
pressure.
• Supply duct static pressure sensor fail -> use constant
volume at minimum air flow.
• Space temperature sensor fail -> use constant
discharge air temperature.
• Space relative humidity sensor fail -> use constant
evaporator leaving temperature.
Expanded Diagnostics
• Refrigerant Pressure Diagnostics (Liquid or Suction) if
they fall outside of acceptable ranges during
operation.
• Water Flow or Temperature Diagnostics for the
outdoor water coil if there is no flow or low
temperature with a demand for heating or cooling
(WSHP only).
• Compressor Run Fail Diagnostics if there is a
command, but not a run status.
• Unit Shutdown Due to Compressor Diagnostics, Heat
Fail, or Condensate Overflow will shut the unit down if
cooling or heating is not working properly and the unit
is supplying well outside of acceptable ranges.
• Return Duct/Space Pressure Source Fail when there is
no input from the transducer.
• Duct Static Pressure Setpoint Range and Return Duct/
Space Pressure Setpoint Range when the setpoints
aren't within an acceptable range in comparison to the
hardwired input. Alarm is shown when setpoint is:
• Above 85% of max range,
• Below min range,
• Below 5% of the difference between the min and
max.
• Outdoor Air Flow Source Fail when the outdoor air
damper is open, supply fan is on, but there's no air flow
reading.
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