Trane OA1D OA2D OA3D (Indirect Gas-Fired/Electric Heat) Maintenance Manual
Sequence of Operation
OAU-SVX01E-EN
23
Discharge Air Control with
Indirect Gas-Fired or Electric Heat
and Modulating HGRH, ERV, and
Powered Ex.
Indirect Gas-Fired or Electric Heat
and Modulating HGRH, ERV, and
Powered Ex.
Sequence of Operation—”Occupied”
Emergency Stop.
When the contacts at Terminal
OAUTS 9 and 10 are open, the unit’s operation will be in
Alarm Status. The Alarm must be reset from either the BAS
or the optional on-board unit display.
Alarm Status. The Alarm must be reset from either the BAS
or the optional on-board unit display.
Alarms must be reset from the optional on-board unit
display or remote BAS to restart the control sequence. If
optional display is not installed; Tracer TU must be used to
diagnose and clear alarm. If Tracer TU is not available,
cycle main power to unit to clear alarm.
display or remote BAS to restart the control sequence. If
optional display is not installed; Tracer TU must be used to
diagnose and clear alarm. If Tracer TU is not available,
cycle main power to unit to clear alarm.
Important:
Cycling power to unit to clear alarm may not
resolve alarm condition.
resolve alarm condition.
Starting Sequence
When 3-phase is powered to unit the main unit controller
and the RTRM will initialize. Initialization process requires
approximately 3 minutes.
and the RTRM will initialize. Initialization process requires
approximately 3 minutes.
The unit is placed in occupied operation via either the BAS
or by closing connection between unit terminals OAUTS 7
and 8. The unit must not be in lockout.
or by closing connection between unit terminals OAUTS 7
and 8. The unit must not be in lockout.
Starting Sequence with No Return Air Damper
Installed
Installed
The outdoor air damper will be commanded to open. The
damper end switch will make causing the main unit
controller to initialize the indoor fan starting sequence by
sending a preset run signal (field adjustable between
50 percent and 100 percent) to the indoor fan VFD. If after
30 seconds the indoor fan proving switch does not prove
the indoor fan on, the main unit controller will command
the indoor fan off and signal an alarm.Starting Sequence
with Optional Return Air Damper Installed
damper end switch will make causing the main unit
controller to initialize the indoor fan starting sequence by
sending a preset run signal (field adjustable between
50 percent and 100 percent) to the indoor fan VFD. If after
30 seconds the indoor fan proving switch does not prove
the indoor fan on, the main unit controller will command
the indoor fan off and signal an alarm.Starting Sequence
with Optional Return Air Damper Installed
Identical to sequence with no return air damper except the
outdoor air and return air dampers will be commanded to
move to their preset occupied positions. Outdoor air
damper end switch is disabled when the return air damper
is installed.
outdoor air and return air dampers will be commanded to
move to their preset occupied positions. Outdoor air
damper end switch is disabled when the return air damper
is installed.
Operating Modes
A. Economizer (Ventilation)
B. Heating
C. Dehumidification
D. Cooling
All modes are enabled by the main unit control module.
The control module calculates dewpoint based on sensed
outdoor air temperature and humidity.
The control module calculates dewpoint based on sensed
outdoor air temperature and humidity.
A. Economizer Mode.
Operation in economizer mode
is enabled when the outdoor air temperature is between
the Outdoor Air Cooling Setpoint and the Outdoor Air
Heating setpoint and no call for dehumidification exists.
Operation in economizer mode continues until outdoor air
conditions call for either dehumidification, cooling or
heating mode.
the Outdoor Air Cooling Setpoint and the Outdoor Air
Heating setpoint and no call for dehumidification exists.
Operation in economizer mode continues until outdoor air
conditions call for either dehumidification, cooling or
heating mode.
B. Heating Mode.
Heating mode is enabled on outdoor
air heating setpoint. The main unit controller will
modulate the heating capacity to maintain the discharge
air heating setpoint. Hot gas reheat is disabled when
heating is enabled. Heating will be disabled at outdoor air
heating setpoint + 2°.
modulate the heating capacity to maintain the discharge
air heating setpoint. Hot gas reheat is disabled when
heating is enabled. Heating will be disabled at outdoor air
heating setpoint + 2°.
C. Dehumidification Mode.
Dehumidification mode is
enabled on outdoor air dewpoint enable setpoint if no call
for heating is enabled. The unit’s controller will activate the
dehumidification mode when outdoor air dewpoint is
higher than or equal to outdoor air dewpoint setpoint.
Compressor control is based on evaporator leaving air
temperature setpoint. With dehumidification enabled, if
evaporator leaving air temperature is above setpoint first
stage dehumidification (Compressor 1) will start. If after a
3-minute minimum delay the evaporator leaving air
temperature is still above the evaporator leaving air
temperature setpoint, the second, third, and fourth stages
of dehumidification (Compressor 2, 3, and 4) will be
staged on sequentially following individual 3-minute
minimum delays between each call. Dehumidification
mode will be disabled at outdoor air dewpoint setpoint
for heating is enabled. The unit’s controller will activate the
dehumidification mode when outdoor air dewpoint is
higher than or equal to outdoor air dewpoint setpoint.
Compressor control is based on evaporator leaving air
temperature setpoint. With dehumidification enabled, if
evaporator leaving air temperature is above setpoint first
stage dehumidification (Compressor 1) will start. If after a
3-minute minimum delay the evaporator leaving air
temperature is still above the evaporator leaving air
temperature setpoint, the second, third, and fourth stages
of dehumidification (Compressor 2, 3, and 4) will be
staged on sequentially following individual 3-minute
minimum delays between each call. Dehumidification
mode will be disabled at outdoor air dewpoint setpoint
- 2°.
During operation in dehumidification mode, the main unit
controller will enable hot gas reheat. Hot gas reheat will
modulate to maintain the discharge air cooling setpoint.
controller will enable hot gas reheat. Hot gas reheat will
modulate to maintain the discharge air cooling setpoint.
C. Cooling Mode.
Cooling mode is enabled on outdoor
air cooling setpoint if no call for heating or
dehumidification is present. Compressor staging is
identical to dehumidification; however, control
temperature is discharge air cooling setpoint. Cooling will
be disabled at outdoor air cooling setpoint - 2°.
dehumidification is present. Compressor staging is
identical to dehumidification; however, control
temperature is discharge air cooling setpoint. Cooling will
be disabled at outdoor air cooling setpoint - 2°.
During operation in cooling mode hot gas reheat is
enabled. Hot gas reheat is controlled to maintain discharge
air cooling setpoint.
enabled. Hot gas reheat is controlled to maintain discharge
air cooling setpoint.
Optional Features
Digital Compressors
Main unit controller will modulate digital compressor to
maintain either evaporator leaving or discharge air
temperature setpoints depending on mode of operation.
Remaining compressors will be staged as described in
mode.
maintain either evaporator leaving or discharge air
temperature setpoints depending on mode of operation.
Remaining compressors will be staged as described in
mode.
ERV and Powered Exhaust
ERV and powered exhaust are interlocked with indoor fan
operation in occupied heating, dehumidification or
cooling modes. Outdoor air sensors sending temperature
and Rh signals to the main unit controller to make mode
operation in occupied heating, dehumidification or
cooling modes. Outdoor air sensors sending temperature
and Rh signals to the main unit controller to make mode