Trane Horizon OABD Series Installation, Operation And Maintenance Manual page 116

Sequence of Operation v12.0
dewpoint calculated enable setpoint but is limited to not rise
above the discharge air temperature setpoint active.
Discharge air temperature setpoint active is reset by
comparing the space temperature to the space temperature
setpoint active. If the hot gas reheat remains at 100% and there
is insufficient reheat to meet the discharge temperature
setpoint, and primary electric heat is installed, the heater may
be energized to provide additional reheat.
Space Control without Outdoor Air Damper
(100% Return Air)
A space dewpoint setpoint is calculated using space
temperature setpoint active and space dehumidification
setpoint (relative humidity). Dehumidification mode is enabled
when the space dewpoint rises above the space dewpoint
calculated enable setpoint (2° deadband). Dehumidification
mode is terminated based on the setpoint deadband.
During dehumidification mode, cooling is controlled to the
dehumidification temperature setpoint active, and hot gas
reheat (if installed) controls to the discharge air temperature
setpoint active. Dehumidification temperature setpoint active
is reset by comparing the space dewpoint to the space
dewpoint calculated enable setpoint but is limited to not rise
above the discharge air temperature setpoint active.
Discharge air temperature setpoint active is reset by
comparing the space temperature to the space temperature
setpoint active.
If the hot gas reheat remains at 100% and there is insufficient
reheat to meet the discharge temperature setpoint, the first
circuit compressor capacity may be increased to provide
additional reheat. If the reheat boost is still not able to meet the
discharge air temperature setpoint and the space becomes
overcooled for an extended period, dehumidification mode will
be terminated to allow the heat to warm the space back to
setpoint.
Space Control with Outdoor Air Damper
A space dewpoint setpoint is calculated using space
temperature setpoint active and space dehumidification
setpoint (relative humidity). Dehumidification mode is enabled
when the space dewpoint rises above the space dewpoint
calculated enable setpoint (2° deadband) or when the outdoor
air dewpoint rises above 60° (3° deadband). Dehumidification
mode is terminated based on the setpoint deadbands for the
space dewpoint or the outdoor air dewpoint.
During dehumidification Mode, cooling is controlled to the
dehumidification temperature setpoint active, and hot gas
reheat (if installed) controls to the discharge air temperature
setpoint active. Dehumidification temperature setpoint active
is reset by comparing the space dewpoint to the space
dewpoint calculated enable setpoint but is limited to not rise
above the discharge air temperature setpoint active.
Discharge air temperature setpoint active is reset by
comparing the space temperature to the space temperature
setpoint active.
If the hot gas reheat remains at 100% and there is insufficient
reheat to meet the discharge temperature setpoint, the first
circuit compressor capacity may be increased to provide
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additional reheat. If the reheat boost is still not able to meet the
discharge air temperature setpoint and the space becomes
overcooled for an extended period, dehumidification mode will
be terminated to allow the heat to warm the space back to
setpoint.
If the space humidity sensor is not installed or is in fault, the
space dewpoint is ignored, and the unit reverts to using only
outdoor air conditions to determine dehumidification, with a
constant dehumidification temperature setpoint of 48°.
Single Zone VAV
A space dewpoint setpoint is calculated using space
temperature setpoint active and space dehumidification
setpoint (relative humidity). Dehumidification mode is enabled
when the space dewpoint rises above the space dewpoint
calculated enable setpoint or when the outdoor air dewpoint
rises above 60° (3° deadband). Dehumidification mode is
terminated based on the setpoint deadbands for the space
dewpoint or the outdoor air dewpoint.
During dehumidification mode, cooling is controlled to the
dehumidification temperature setpoint active, and hot gas
reheat (if installed) controls to the discharge air temperature
setpoint active. Dehumidification temperature setpoint active
is reset by comparing the space dewpoint to the space
dewpoint calculated enable setpoint but is limited to not rise
above the discharge air temperature setpoint active. The
discharge air temperature setpoint active and supply fan
speed are reset based on space temperature. Refer to (supply
fan section) to see a detailed explanation.
If the hot gas reheat remains at 100% and there is insufficient
reheat to meet the discharge temperature setpoint, the first
circuit compressor capacity may be increased to provide
additional reheat. If the reheat boost is still not able to meet the
discharge air temperature setpoint and the space becomes
overcooled for an extended period, dehumidification mode will
be terminated to allow the heat to warm the space back to
setpoint.
If the space humidity sensor is not installed or is in fault, the
space dewpoint is ignored, and the unit reverts to using only
outdoor air conditions to determine dehumidification, with a
constant dehumidification temperature setpoint of 48°.
Discharge Control with Outdoor Air Damper
Dehumidification mode is enabled when the outdoor air
dewpoint rises above the outdoor air dewpoint setpoint (adj.)
and is terminated when the outdoor air dewpoint falls 3° below
setpoint. During dehumidification mode, cooling is controlled
to the dehumidification temperature setpoint active, and hot
gas reheat (if installed) controls to the discharge air
temperature setpoint active.
Discharge Control without Outdoor Air
Damper (100% Return Air)
Dehumidification mode is enabled when the return air
dewpoint rises above the return air dewpoint setpoint (adj.) and
is terminated when the return air dewpoint falls 3° below
setpoint. During dehumidification mode, cooling is controlled
to the dehumidification temperature setpoint active, and hot
OAU-SVX007A-EN