Trane OA1D OA2D OA3D (Indirect Gas-Fired/Electric Heat) Maintenance Manual
Sequence of Operation
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OAU-SVX01E-EN
Optional Features
Digital Compressors
Main unit controller will modulate digital compressor to
maintain either evaporator leaving or space temperature
setpoints depending on mode of operation. Remaining
compressors will be staged as described in mode.
maintain either evaporator leaving or space 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
calls are relocated downstream of the ERV. Outdoor air
heating and dehumidification override setpoints will be
based on ERV leaving conditions. Additional sensors will
be installed in the non-ERV outdoor air position for
information purposes and those outdoor air readings may
be viewed at the main unit controller or via the BAS. When
operating in economizer mode the ERV is disabled and the
ERV by-pass damper(s) open, powered exhaust remains
on and is adjusted to 100 percent capacity by the main unit
controller. The main unit controller will end ERV operation
and open ERV bypass dampers if outdoor air/return air
conditions could cause ERV frosting, powered exhaust
remains on.
operation in occupied heating, dehumidification or
cooling modes. Outdoor air sensors sending temperature
and Rh signals to the main unit controller to make mode
calls are relocated downstream of the ERV. Outdoor air
heating and dehumidification override setpoints will be
based on ERV leaving conditions. Additional sensors will
be installed in the non-ERV outdoor air position for
information purposes and those outdoor air readings may
be viewed at the main unit controller or via the BAS. When
operating in economizer mode the ERV is disabled and the
ERV by-pass damper(s) open, powered exhaust remains
on and is adjusted to 100 percent capacity by the main unit
controller. The main unit controller will end ERV operation
and open ERV bypass dampers if outdoor air/return air
conditions could cause ERV frosting, powered exhaust
remains on.
Note: For units with optional ERV defrost heater, the
control sequence will engage heater at frost
condition rather than stop ERV.
condition rather than stop ERV.
The powered exhaust fan speed is factory set to run
between 50 percent and 100 percent (field adjustable).
between 50 percent and 100 percent (field adjustable).
Hot Gas Reheat
Following continuous 30-minute hot gas reheat operation
at less than 100 percent reheat capacity a purge cycle will
be initiated. During the purge cycle the, hot gas reheat
signal is set and held at 100 percent for a period of
3 minutes. Following the purge cycle, normal operation
resumes.
at less than 100 percent reheat capacity a purge cycle will
be initiated. During the purge cycle the, hot gas reheat
signal is set and held at 100 percent for a period of
3 minutes. Following the purge cycle, normal operation
resumes.
Sequence of Operation—”Unoccupied”
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.
Starting Sequence
Indoor fan proving sequence is identical to occupied
operation.
operation.
Starting Sequence with Optional Return Air
Damper Installed
Damper Installed
The outdoor air damper will be commanded to close and
the return air damper will open. Outdoor air damper end
switch is disabled when the return air damper is installed.
the return air damper will open. Outdoor air damper end
switch is disabled when the return air damper is installed.
Starting Sequence with No Return Air Damper
Installed.
Installed.
Identical to occupied sequence no return air
damper installed.
Operating Modes
A. Unoccupied Heating
B. Unoccupied Dehumidification
C. Unoccupied Cooling
A. Heating Mode.
Unoccupied heating is enabled
based on unoccupied space heating setpoint. Unoccupied
heating is enabled when space temperature reaches
unoccupied space heating setpoint - 2°. The modulating
gas heat or SCR electric heat will continue to raise the
discharge air temperature to a maximum of 90°F and
continue to supply heated 90° air to the space until the
space temperature reaches setpoint + 2°. Unit operation is
discontinued when unoccupied space heating is satisfied.
heating is enabled when space temperature reaches
unoccupied space heating setpoint - 2°. The modulating
gas heat or SCR electric heat will continue to raise the
discharge air temperature to a maximum of 90°F and
continue to supply heated 90° air to the space until the
space temperature reaches setpoint + 2°. Unit operation is
discontinued when unoccupied space heating is satisfied.
B. Dehumidification Mode.
When no call for
unoccupied heating exists, unoccupied dehumidification
is enabled based on unoccupied space dewpoint setpoint.
During unoccupied dehumidification operation
dehumidification capacity is restricted to 50 percent (only
half of the compressors are allowed to come on).
Unoccupied dehumidification is enabled when space
temperature reaches unoccupied space dehumidification
setpoint + 1°. Dehumidification stops at setpoint - 1°. Unit
operation is discontinued when unoccupied space
dehumidification is satisfied.
is enabled based on unoccupied space dewpoint setpoint.
During unoccupied dehumidification operation
dehumidification capacity is restricted to 50 percent (only
half of the compressors are allowed to come on).
Unoccupied dehumidification is enabled when space
temperature reaches unoccupied space dehumidification
setpoint + 1°. Dehumidification stops at setpoint - 1°. Unit
operation is discontinued when unoccupied space
dehumidification is satisfied.
C. Cooling Mode.
When no call for unoccupied heating
or unoccupied dehumidification exists, unoccupied
cooling is enabled based on unoccupied space cooling
setpoint. During unoccupied space cooling operation
cooling capacity is restricted to 50 percent (only half of the
compressors are allowed to come on). Unoccupied
cooling is enabled when space temperature reaches
unoccupied space cooling setpoint + 2°. Cooling stops at
setpoint - 2°. Unit operation is discontinued when
unoccupied space cooling is satisfied.
cooling is enabled based on unoccupied space cooling
setpoint. During unoccupied space cooling operation
cooling capacity is restricted to 50 percent (only half of the
compressors are allowed to come on). Unoccupied
cooling is enabled when space temperature reaches
unoccupied space cooling setpoint + 2°. Cooling stops at
setpoint - 2°. Unit operation is discontinued when
unoccupied space cooling is satisfied.
Powered Exhaust/ERV Sequence of Operation
Powered Exhaust/ERV operation is disabled during unit
“Unoccupied” operating modes.
“Unoccupied” operating modes.