Supplemental Hot Water Reheat; Hot Water Reheat (No Hot Gas Reheat Installed); Exhaust Fan Operation With Isolation Exhaust Fan Damper(S); Without Isolation Exhaust Fan Dampers - Trane Horizon OADG Series Installation, Operation And Maintenance Manual

Sequence of Operation
be used to maintain the Discharge Air Temperature
Setpoint Active.

Supplemental Hot Water Reheat

If the Hot Gas Reheat Valve Command is at 100%, the hot
water valve is energized with Heating Capacity at 0%. If
Heat Capacity rises above 0%, the Hot Gas Reheat Valve
Command will be locked at 100% and the hot water will be
used to maintain the Discharge Air Temperature Setpoint
Active.
Hot Water Reheat (No Hot Gas Reheat
Installed)
During Dehumidification Mode, the hot water valve is
energized by enabling Heat 1 Command, Heat Capacity is
adjusted to maintain Discharge Air Temperature Setpoint
Active.
Exhaust Fan Operation
With Isolation Exhaust Fan Damper(s)
After completing the Supply Fan Starting Sequence,
Exhaust Damper Open Close Command is enabled. Once
the Exhaust Damper End Switch has proven, Exhaust Fan
Start Stop Command is enabled.

Without Isolation Exhaust Fan Dampers

After completing the Supply Fan Starting Sequence,
Exhaust Fan Start Stop Command is enabled.

With Modulating OA/RA Dampers

Exhaust fan speed is controlled to Duct/Space Pressure
Setpoint.

ECM Exhaust with 2-Position OA Damper

Using the Exhaust Air Flow Active from the exhaust fan
piezo reading, the unit controls exhaust fan speed to a
constant volume of according to the Exhaust Air Flow
Setpoint.

VFD Exhaust with 2-Position OA Damper

The exhaust fan controls to a constant speed using PEVFD
Setpoint.
Energy Recovery Wheel
Operation (ERV)
The Energy Recovery Wheel Start Stop Command is
enabled whenever there is a call for exhaust fan. During
Ventilation Mode or Economizer Mode the ERV is disabled,
except during the cleaning cycle, which occurs for two
minutes every thirty minutes.
During cooling operation, the Energy Recovery Exhaust
Air Bypass Position Command is locked at 0% (closed
position) for full energy recovery. During heating
84
operation, the position is modulated to maintain the
Discharge Air Temperature Setpoint Active for variable
effectiveness capacity control. Once the bypass damper
becomes fully closed, the primary heater will be engaged.

Energy Wheel Without VFD

The unit prevents frost accumulation on the ERV by
measuring the Exhaust Leaving Temperature Local. The
Energy Recovery Outdoor Air Bypass Position Command
is modulated open to maintain 15°F for the exhaust
temperature. Above this temperature, the bypass damper
will remain at 0% signal (closed) when the ERV is in
operation.

Energy Wheel With VFD

The unit prevents frost accumulation on the ERV by
measuring the Exhaust Leaving Temperature Local.
Initially the ERV speed is reduced to maintain 15°F for the
exhaust temperature. If the ERV speed is at minimum, but
the exhaust temperature remains below 15°F, the unit will
maintain the temperature by modulating the Energy
Recovery Outdoor Air Bypass Position Command open.
During normal operation, the VFD is at 100% (full speed)
and the bypass damper is at 0% (closed).

Additional Features

Electric Pre-Heat

Pre-Heat Enable is engaged whenever the Exhaust
Leaving Temperature Local falls below 20°F, with a
deadband of 5°F. The pre-heater is shut off if the Preheat
Leaving Temperature Local rises above 90°F.

Space Thumbwheel Input

Space Control and Single Zone VAV
With a space thumbwheel installed, the Occupied Heating
Setpoint and Occupied Cooling Setpoint is replaced with a
single setpoint from the input Space Temperature Setpoint
Local. The occupancy override button will override
Occupancy Request to Occupied for two hours from the
time it was pressed.

Split Exhaust and Return Air Path

When a unit is equipped with separate paths for the return
and exhaust air, there will be a damper separating the two,
and the powered exhaust shall not run below the
minimum required speed to ensure exhaust air does not
contaminate the supply air. A differential pressure sensor
is used across the damper to verify a negative pressure on
the exhaust side. Exhaust fan will be enabled during
unoccupied mode. During Economizer Mode the damper
between the two air paths will open, the return damper will
close complete, and the outdoor damper will open to
100%.
OAU-SVX006E-EN