61
YORK INTERNATIONAL
FORM 100.50-NOM1 (604)
5
Morning Warm Up
Morning Warm Up operation is carried out when:
• The
Morning Warm Up
parameter is ON.
• The
Internal Clock/Schedule
pa ram e ter is ON.
• Occupancy is scheduled for the cur rent day.
• Warm up command is received from BAS.
The Morning Warm Up start time will be 60 minutes
prior to scheduled occupancy, or BAS initiates the
morn ing warm-up.
When started, the Morning Warm Up operation is as
follows:
• Close economizer.
• Turn the Supply Fan ON and operate for 2 min utes
before beginning temperature control.
• If the RAT is 2 degrees less than the Morning Warm
Up setpoint, the Primary Unit Controller will en-
ergize the heat relays and bring on all stages after
one minute.
• For stepped heating - Control to maintain the RAT to
the Morning Warm Up Setpoint using the algorithm
il lus trat ed in Fig ure 26.
• For Hydronic heating - The SAT is controlled to the
2
nd
Stage Hy dro Heat Setpoint.
Morning Warm Up operation will end when:
• An occupancy (space is oc cu pied) input is re ceived
from the controller input.
• The scheduled occupancy time occurs.
• The Morning Warm Up operation times out based
on the
"Max Warm Up Time"
pa ram e ter if warm up
signal is controlled by a BAS signal.
Supply Air Tempering
VAV Supply Air Tempering operation requires the fol-
low ing:
• Economizer – ON
• Unit is equipped with electric, gas, steam or
hydronic heat
• Heat Enable - ON
• Economizer Enable – ON
• Conditions are suitable for Econ o miz er op er a tion
• Supply Air Tempering Enable – ON
• All compressors – OFF
Supply Air Tempering is a continuation of the VAV
cooling operation when the Outdoor Air Temperature
is below the SAT set point, where heating is used to
maintain ventilation operation.
Supply Air Tempering With Proportional Heat
If the unit is equipped with proportional heat, Hot Wa-
ter, Steam, or Modulating Gas, the control will provide
Supply Air Tem per ing:
• When the SAT falls below the (SAT setpoint – 10°F)
for 10 minutes.
• The control will control the Heating Valve an a log
out put to maintain the current
"VAV Cool High
Temp"
Set point.
The control will end Supply Air Tempering operation
and begin Cooling operation when the SAT rises to 4°F
above the
"VAV Cool High Temp"
setpoint.
Supply Air Tempering With Staged Heat
If the unit is equipped with stepped heat (electric or
gas), the heat stages will be duty cycled to maintain
SAT setpoint.
The duty cycle for the heat steps will be:
• A 10-minute period;
• A minimum time of 2 minutes ON;
• A minimum time of 1 minute OFF.
Table 17 details the modes of VAV operation and
pro vides an overview of the control methods in all
modes.
5
FIG. 30 –
OCCUPIED HEATING AND COOLING
SETPOINT SELECTION ALGORITHM
Enable VAV
Low Temp.
Setpoint For
Cooling
Enable VAV
High Temp.
Setpoint For
Cooling
Enable VAV
Occupied
Hearing (If
Allowed)
-2.0˚F
-1.5˚F
-0.5˚F
VAV Setpoint
For SAT Reset
+2.0F
SPACE TEMPERATURE
LD06561