Controlling Excessive Sat (Supply Air Temperature); Holiday Schedule - York MILLENIUM SIMPLICITY ELITE Series Technical Application And Programming Manual

Table 12: Holiday Schedule
Holiday Number Start Month
Holiday 1 00
Holiday 2 00
Holiday 3 00
Holiday 4 00
Holiday 5 00
Holiday 6 00
Holiday 7 00
Holiday 8 00
Holiday 9 00
Holiday 10 00
Holiday 11 00
Holiday 12 00
Holiday 13 00
Holiday 14 00
Holiday 15 00
Holiday 16 00
Holiday 17 00
Holiday 18 00
Holiday 19 00
Holiday 20 00
Full heating (all stages) is ON when RAT drops 2 °F below the
setpoint, heating is OFF when RAT is at, or above the setpoint.
(Note that in this case, the control will use all available heating
stages, regardless of setting of the programmable parameter
"Heat Stages"). Before energizing heat for Morning Warm Up
the control will start the Fan and operate it for 5 minutes. The
Economizer will stay closed and the Fan will continue to run
during the Morning Warm Up. The Morning Warm Up will
terminate when the Occupied period begins.
If the RAT setpoint is achieved before the MWU period expires,
Unoccupied cooling is permitted. If further heating is needed
during the Occupied period, it is controlled by a VAV Occupied
Heating algorithm (if enabled and if a Space Sensor is used), or
by a space thermostat.
The same algorithm is also used for VAV Occupied Heating
(see also paragraph "VAV Occupied heating" in "Option
Operation" section earlier in this document). In this case, the
VAV Occupied Heating control algorithm is activated under the
control of the Space Sensor (whenever the zone temperature
sensed by the Space Sensor drops 2 °F or more below a
programmed "VAV SAT Reset Setpoint"). Once activated, the
Johnson Controls Unitary Products
Start Day Number
Start Time
of Month of Days
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
00 00:00 00
Occupied Heating control algorithm controls RAT between the
MWU RAT Setpoint and two degrees below the setpoint and
cycles the fan the same way as the MWU algorithm.
The specified Max Morning Warm Up Time is not used to limit
the duration of VAV Occupied Heating. During heating for
Morning Warm Up, or for VAV Occupied heating function, the
VAV boxes controls will receive an override signal to open the
VAV box damper. This is accomplished by wiring the VAV heat
relay for the VAV boxes to open, and energizing it from Heat
output of the controller. Note that as the first stage of heat
cycles on / off, the VAV box heat relay will cycle with it.
UNOCCUPIED VAV HEATING / COOLING CONTROL
ALGORITHM WITH A SPACE SENSOR
In the unoccupied mode, the Space Sensor will compare the
temperature in a selected VAV zone to the programmed
Unoccupied Heating and Cooling setpoints and request heating
or cooling using the following control algorithm:
OCCUPIED VAV HEATING / COOLING CONTROL
ALGORITHM WITH A SPACE SENSOR
In the occupied mode, the control will compare the temperature
in a selected VAV zone to the programmed "VAV SAT Reset
Setpoint" and request heating or cooling using the following
control algorithm: The transition from cooling to occupied
heating occurs at 2 °F below the "VAV SAT Reset Setpoint".
There is no "satisfied", or "idle" state of the unit between cooling
and occupied heating.
The above algorithm only requests occupied cooling and
selects a SAT occupied cooling setpoint, or requests occupied
heating at a programmed "Morning Warm Up RAT Setpoint".
Once requested by this Space Sensor algorithm, the cooling is
controlled by the SAT control algorithm described in paragraph
"SAT Control Algorithm in VAV Cooling" earlier in this section
[not to be found by that name...]. Once requested by this Space
Sensor algorithm, the occupied heating is controlled by the RAT
control algorithm described in paragraph "Morning Warm Up /
VAV Occupied Heating Control Algorithm" earlier in this section.
CONTROLLING EXCESSIVE SAT (SUPPLY AIR
TEMPERATURE)
This is required in cooling operation in order to prevent a
danger of "slugging" and damage to the DX compressors.
Rooftop units do not use accumulators on compressor intake,
and liquid refrigerant could enter the intake of a compressor in
case of a low heat transfer on the evaporator coil. In heating
operation, the Excessive SAT control is not used.
SAT CONTROL CONFIGURATION
SAT control for cooling is configurable to enable or disable
(on/off). The default setting for cooling is ON. The user is not
normally expected to turn this mode OFF, but the possibility of
turning it OFF is provided mainly for troubleshooting purposes.
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