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YORK INTERNATIONAL
58
Controls (continued)
mine if conditions are suitable for economizing and
modulate the outside air damper and/or stage up com-
pressors as required to maintain the VAV High Supply
Air Temperature Setpoint. This setpoint is user select-
able at the OptiLogic
™
User Interface. The OptiLogic
™
controller will control to this setpoint as long as Cooling
Stage 1 (“Y1”) remains active.
When a Cooling Stage 2 call (“Y2”) is received, and the
unit is equipped with an economizer, the OptiLogic
™
controller will check the Outside Air conditions to deter-
mine if conditions are suitable for economizing and
modulate the outside air damper and/or stage up com-
pressors as required to maintain the VAV Low Supply
Air Temperature Setpoint. This setpoint is user select-
able at the OptiLogic
™
User Interface. The OptiLogic
™
controller will control to this setpoint as long as Cooling
Stage 2 (“Y2”) remains active.
The VAV High SAT Setpoint is always greater than the
VAV Low SAT Setpoint and because of this essentially
makes this control sequence a Supply Air Temperature
Reset algorithm based on Zone Temperature or Out-
side Air.
Zone Sensor Control
When a VAV unit is configured for Zone Sensor opera-
tion, the OptiLogic
™
controller will monitor a reference
Zone Temperature and command the Supply Fan to
start when the unit goes into the Occupied mode.
If the zone temperature is above the VAV Setpoint for
SAT Reset, the OptiLogic
™
controller will modulate the
outside air damper (Economizer available and condi-
tions suitable) and/or stage compressors up and down,
as required, to maintain the VAV High Supply Air Tem-
perature Setpoint.
If the zone temperature is below or falls below the VAV
Setpoint for SAT Reset, the OptiLogic
™
controller will
modulate the Outside Air Damper (Economizer avail-
able and conditions suitable) and/or stage compres-
sors up and down, as required, to maintain the VAV
High Supply Air Temperature Setpoint.
As with thermostat operation, this sequence is also a
Supply Air Temperature Reset algorithm based on Zone
Temperature.
Stand-Alone Control
If the unit is not configured for Thermostat or Zone Sen-
sor operation, the unit will operate in Stand-Alone Mode.
In Stand-Alone Mode, the OptiLogic
™
Controller will
monitor only the Occupied/Unoccupied state. When the
unit is commanded into the Occupied Mode of opera-
tion, the OptiLogic
™
Controller will start the Supply Fan.
If the unit is equipped with an Economizer, the Con-
troller will check to see if Outside Air conditions are
suitable for Economizing. The controller will then use
Outside Air (when available and suitable) and/or stage
compressors up and down, as required, to maintain
the VAV Low SAT Setpoint.
Supply Air Tempering
Supply Air Tempering is a continuation of the a VAV
cooling operation when the outside air temperature is
below the supply air temperature setpoint where heat-
ing is used to maintain economizer operation. This func-
tion will use small increments of heat to maintain the
Supply Air Temperature when the economizer damper
is at minimum position. If the unit is equipped with
stepped heat (electric or gas), the heat will be duty
cycled. A maximum of six cycles per hour is permitted
for the heating stages.
HEATING OPERATION
VAV Occupied Heating
When VAV Occupied Heating is enabled, full heating
will energize when either the thermostat W1 or W2 sig-
nal is received or the space temperature falls below
the VAV Setpoint for SAT Reset by more than -16.6°C.
If the return air temperature falls below the return air
temperature setpoint for occupied heating, full heat ca-
pacity will be energized.
CV SPECIFIC SEQUENCES
COOLING OPERATION
Thermostat Control
If a 7-wire thermostat (2 Cool/2 Heat) controls the unit,
all zone temperature setpoint control is maintained at
the thermostat. With this operation, the unit remains
idle until it receives a stage call from the thermostat. If
“G” is called from the thermostat, the Supply Fan will
start. Ventilation functions (if equipped) will be permit-
ted to run with an occupied signal. Economizer func-
tions will operate with a “G” call and a call for cooling.