Trane Horizon OADG Series Installation, Operation And Maintenance Manual page 78

Attention Startup or Service Technician
Horizon UC600 v11.0 Released
The programming has gone through an overhaul. Take a
moment to read through the Sequence of Operation
included in this packet to familiarize yourself with the new
operation.
Note: Program v11.0 is not backwards compatible with
previous Horizon units. The point configuration has
changed, and suction pressure transducers are
required for proper operation.
In the future, a package will be made available
that's backwards compatible with units
manufactured after Jan 1st, 2019.
Documents Included in This Packet:
1. Sequence of Operation – Full Horizon sequence, not
unit-specific.
2. New Startup Form
3. Unit-Specific Points List – Points not relevant to the unit
have been removed from this document.
Unchanged from Previous Versions:
• All programming and points built in. UC600
determines sequence based on configurable points
and what points are Out of Service (mostly Analog and
Binary Inputs/Outputs).
• Verifying setpoints with the customer is
recommended.
Summary of Improvements
Suction Pressure Monitoring
All units with compressors will come standard with a
refrigeration suction pressure transducer on circuit one.
Units with digital scroll on the second circuit will also have
a transducer on the second circuit.
Suction pressure will be used during cooling and
dehumidification to limit capacity to prevent frost on the
evaporator. An informational diagnostic will be displayed
if this occurs repeatedly.
Compressor Run Status and Diagnostics
Each compressor will now have a run status by using the
compressor auxiliary contactor. A diagnostic will be
displayed if there is a call for a compressor with no status.
Updated Point Names to Match Tracer SC
Where possible, all points will be updated so that they
match with standard Tracer SC key names.
Evaporator Leaving Temperature Setpoint
Reset
Single Zone VAV and Space Control units: During
78
dehumidification mode the unit will reset the evaporator
setpoint by comparing the space conditions to the
setpoints. Previously a fixed setpoint for the evaporator
temperature was used during dehumidification.
Minimum Supply Air Flow Setpoints
VAV units will now have separate minimum air flows
during heating or cooling operation. Previously, the
setting used was the highest value for all modes of

operation. If these values are lower than a minimum
outdoor air flow setpoint, then the outdoor air setpoint is
used.
Single Zone VAV Mod. Air Flow - Heating
Mode
Single Zone VAV will now modulate supply air flow to
maintain space temperature. Previously it was constant
volume during heating mode.
Gas Heater Staging Off at Minimum
Capacity
The first stage of gas heat will now stage off if the heat
capacity is at minimum. Previously, the first stage of heat
was locked on whenever the unit was in heating mode. 2-
minute delays have been added to prevent short cycling.
Reduced Hot Gas Reheat Purge Mode
Previously, if the hot gas reheat was above 0% for 30
minutes, it entered a 3-minute purge cycle at 100% signal.
Now, if the hot gas reheat is between 10% and 50% for 30
minutes, it will enter a 2-minute purge cycle. First half is at
80% signal, second half is at 10% signal.
Unit Shutdown Due to Condensate
Overflow
If the condensate overflow switch signals an alarm, and
the unit is far from meeting setpoint, the unit is shut down
and a diagnostic is displayed. Condensate switch required.
Liquid Line Pressure Setpoint Reset
For maximum efficiency, the liquid line pressure setpoint
defaults to 325PSI during regular cooling mode. During
dehumidification it resets to 450PSI for maximum reheat
capacity in all conditions. Head Pressure Control is
required.
Modulating ERV Exhaust and Outdoor Air
Bypass
All units with an Energy Recovery Wheel (ERV) will now
have modulating bypass for both the outdoor (OA) and
exhaust air (EA). Modulating OA bypass is used to prevent
frosting of the ERV. Modulating EA bypass operates with
the primary heater and is used to prevent overheating on
mild days.
OAU-SVX006E-EN