Trane Horizon OADG Series, Installation, Operation And Maintenance Manual

Page: 81 / 96

Sequence of Operation
OAU-SVX006E-EN 81
Single Zone VAV Control
After completing the starting sequence, the unit adjusts
supply fan speed to maintain
Space Temperature Active to
Space Temperature Setpoint Active . When the unit is in
Dehumidification Mode , the unit adjusts the supply fan
speed to maintain the Space Dewpoint to the Space
Dewpoint Calculated Enable Setpoint .
Supply fan speed is limited between Supply Air Flow
Minimum Setpoint Active and Supply Air Flow Maximum
Setpoint (both factory set).
Field Enabled Space Pressure Control
Units ordered as constant volume can be field enabled to
control the supply fan speed to a pressure input.
Duct
Static Pressure Local must be put In Service, configured,
and referenced to an open input using Tracer TU. The
program will automatically adjust supply fan speed to
maintain
Duct Static Pressure Setpoint BAS .
Economizer Mode
Economizer Mode is enabled when the Outdoor Air
Enthalpy falls below Return Air Enthalpy and the Outdoor
Air Temperature Active is below 80°F. Economizer Mode
continues with a deadband of 3 BTU/lb, and 1°F for
temperature. If the unit is not in
Free Cooling Mode during
Economizer Mode , the unit opens the outdoor air damper
to the Outdoor Air Damper Maximum Position Setpoint .
Mechanical cooling will not be locked out unless the unit
is in
Free Cooling Mode .
Refer to Multi-State Value Economizer System Status to
determine the active status for the economizing.
Free Cooling Mode is enabled when the unit is in
Economizer Mode and the Outdoor Air Temperature
Active is cooler than five degrees below the Discharge Air
Temperature Setpoint Active . During Free Cooling Mode ,
mechanical cooling is locked out and the unit adjusts the
outdoor air damper position to maintain the
Discharge Air
Temperature Setpoint Active .
Ventilation Mode
Discharge Air Control
Ventilation Mode is enabled when the Outdoor Air
Temperature Active is between the Outdoor Air Cooling
Enable Setpoint and the Outdoor Air Heating Enable
Setpoint . During Ventilation Mode , heating and cooling is
locked out and the unit supplies un- conditioned air.
Ventilation Mode is locked out whenever the unit is in
Dehumidification Mode .
Multi-Zone VAV Control
Ventilation Mode locked out.
Space Control
Ventilation Mode is enabled when the Outdoor Air
Temperature Active and the Space Temperature Active is
within two degrees of the Space Temperature Setpoint
Active . During Ventilation Mode , heating and cooling is
locked out and the unit supplies un- conditioned air.
Ventilation Mode is locked out whenever the unit is in
Dehumidification Mode .
Single Zone VAV Control
Ventilation Mode is enabled when the Outdoor Air
Temperature Active and the Space Temperature Active is
within two degrees of the Space Temperature Setpoint
Active . During Ventilation Mode , heating and cooling is
locked out, the supply fan goes to minimum air flow, and
the unit supplies un-conditioned air.
Ventilation Mode is
locked out whenever the unit is in Dehumidification Mode .
Primary Heating Mode
Discharge Air Control
Heating Mode is enabled whenever the Outdoor Air
Temperature Active is below the Outdoor Air Heating
Enable Setpoint . During Heating Mode, Heat Capacity is
adjusted to maintain the Discharge Air Temperature Local
to Discharge Air Temperature Setpoint Active .
Multi-Zone VAV Control
Heating Mode is enabled according to the graph shown in
Figure 51, p. 82 . Using the graph, setpoint is Discharge Air
Temperature Setpoint Active , offset is 2°F, and
temperature is Discharge Air Temperature Local .
Dehumidification Mode takes priority over Heating Mode.
During Heating Mode, Heat Capacity is adjusted to
maintain the Discharge Air Temperature Local to
Discharge Air Temperature Setpoint Active .
Space Control or Single Zone VAV Control,
with Energy Recovery Wheel or has Mixed
Air
Heating Mode is enabled according to the graph shown in
Figure 51, p. 82 . Using the graph, setpoint is Space
Temperature Setpoint Active , offset is Occupied Offset ,
and temperature is Space Temperature Active .
Dehumidification Mode takes priority over Heating and
Cooling Mode. During Heating Mode, Heat Capacity is
adjusted to maintain the Discharge Air Temperature Local
to Discharge Air Temperature Setpoint Active .