Trane Horizon OADG Series Installation, Operation And Maintenance Manual page 80

Sequence of Operation
Sequence of Operation
General
Text shown in italics are point names in the programming.
Typically, points ending with "Local" are hardwired
inputs, points ending with "Active" are determined by the
program and can't be adjusted by the operator or BAS.
Discharge Air Temperature Setpoint Maximum is
adjustable but cannot exceed 120°F for gas, heat pump, or
hot water heating, and 90°F for electric heating.
Program Control Type can be determined using Multi-
State Value 13.
Note: There is a 3-minute delay during compressor or gas
heater staging to allow the system to stabilize
before adjusting the cooling or heating capacity.
Program-Controlled Setpoints
Space Control and Single Zone VAV
Control
Discharge Air Temperature Setpoint Active is reset by
comparing the Space Temperature Active to Occupied
Cooling Setpoint during cooling and Occupied Heating
Setpoint during heating. If a single setpoint is preferred,
use Space Temperature Setpoint BAS by putting it In
Service using Tracer TU or BAS.
Dehumidification Temperature Setpoint Active is reset by
comparing the Space Dewpoint to the Space Dewpoint
Calculated Enable Setpoint minus 2°F.
If Space Temperature Setpoint BAS or Space Temperature
Setpoint Local (Thumbwheel) is In Service, Occupied
Offset is adjustable (2°F default). Otherwise, is determined
using Occupied Cooling Setpoint and Occupied Heating
Setpoint.
If Occupied Cooling Setpoint is below Occupied Heating
Setpoint, Occupied Offset is 1°F. If Occupied Cooling
Setpoint is above Occupied Heating Setpoint¸ Occupied
Offset is the difference between the two setpoints.
Space Dewpoint Calculated Enable Setpoint is calculated
using Space Humidity Setpoint and Space Temperature
Setpoint Active.
Discharge Air Control and Multi-Zone VAV
Control
Discharge Air Temperature Setpoint Active is controlled by
Discharge Air Cooling Setpoint BAS during cooling
operation, and Discharge Air Heating Setpoint BAS during
heating. If Discharge Air Temperature Setpoint BAS is In
Service, the program will use this over the discharge
cooling and heating setpoints.
Dehumidification Temperature Setpoint Active is
controlled by Dehumidification Temperature Setpoint.
80
Occupied Control
Starting Sequence
Occupied operation begins when the unit is placed in
Occupied via BAS or when OAUTS-7 & 8 is closed on the
field wiring terminal strip. The unit must not be in
Emergency Stop to begin starting sequence. OAUTS-9 &
10 on the field wiring terminal strip are used as an external
Emergency Stop for the unit. Cycling power to unit to may
not resolve alarm condition.
Refer to Multi-State Value Occupancy Status to determine
the active status of the unit.
Two-Position Outdoor Air Damper will begin by
energizing relay OADR, opening the outdoor air damper.
The supply fan sequence begins once the end switch is
closed.
Two-Position Outdoor and Return Air Dampers will
begin by energizing relay OADR, opening the outdoor air
damper and closing the return air damper. The supply fan
sequence starts immediately after the unit becomes
occupied.
Modulating Outdoor and Return Air Dampers will
begin by adjusting the Outdoor Air Damper Position
Command to meet the Outdoor Air Damper Minimum
Position Setpoint. The supply fan sequence starts
immediately after the unit becomes occupied.
Supply Fan Sequence
Supply Fan Starting Sequence begins by energizing
relay G and setting the Supply Fan Speed Command to
50%. The supply fan status switch (IFFS) closes, energizing
relay IFFR. If after two minutes there is no proven signal,
Diagnostic: Supply Fan Failure will be displayed, and the
unit will shut down requiring a manual reset.
Constant Volume with VFD
After completing the starting sequence, the supply fan will
run to the Supply Fan Speed Setpoint, field adjustable
from 50-100% (defaulted 100%).
Constant Volume with ECM
After completing the starting sequence, the unit calculates
the Supply Fan Air Flow Active and adjusts Supply Fan
Speed Command to maintain the Supply Fan Air Flow
Setpoint (adjustable, factory set according to submittal).
Multi Zone VAV Control
After completing the starting sequence, the unit adjusts
fan speed to maintain Duct Static Pressure Active to Duct
Static Pressure Setpoint BAS. Supply fan speed is limited
between Supply Air Flow Minimum Setpoint Active and
Supply Air Flow Maximum Setpoint (both factory set).
OAU-SVX006E-EN