Orion System SA Controller - Manual (Page 45)

SA Controller Technical Guide
Sequence of Operations
45
Morning Warm-Up Mode
For Morning Warm-Up application, the unit must be confi gured as a
VAV unit (Supply Air Temperature control). When the SA Controller
switches to the Occupied Mode of Operation (not Override Mode), the
unit compares the Entering Air Temperature to a Morning Warm-Up
Target Temperature. If the Entering Air Temperature is below this Set-
point, the Warm-Up Mode is initiated. This Mode remains in effect until
the Entering Air Temperature rises above the Target Temperature or a
user-adjustable Time Period expires. Warm-Up Mode is not initiated by
Push-Button Overrides or Unoccupied Heating demands.
Once the Warm-Up Mode has been terminated, it cannot resume until
the unit has been through a subsequent Unoccupied Mode. Only one
Warm-Up Mode is allowed per Occupied cycle.
If you have stand-alone VAV boxes that need to be forced wide open
during the Warm-Up Mode, you can confi gure one of the relay outputs
to be used during this Mode. If the Warm-Up Mode is active, the relay
is activated. This relay then becomes the Force Open Command for all
VAV boxes to which it is wired.
Off Mode
If the schedule has set the Unoccupied Mode and no Heating, Cooling,
or Dehumidifi cation demands exist, the SA Controller enters the Off
Mode. During the Off Mode, the Supply Fan is off.
Supply Air Temperature Setpoint Reset
The SA Controller incorporates a dynamic Supply Air Temperature Reset
function based on a selected Reset Source. The available Reset Source
options are Space Temperature, Entering Air Temperature, Supply Fan
VFD Signal, or a Remote Reset Signal. In each case, for the heating
mode and the cooling mode, a Low and a High Reset Source Setpoint
must be entered that will correspond to a Low and High Supply Air
Setpoint. Since the Supply Air Setpoints are not fi xed during reset, we
refer to them as the “Active Supply Air Temperature Setpoints.” The
SA Controller uses the HVAC Mode Enable Setpoints to determine the
mode of operation. Once the HVAC Mode has been determined, the SA
Controller will proportionally reset the Supply Air Temperature Setpoint
based on the Reset Source condition relative to the Reset Source Low and
High Setpoints. For each of the Reset Source options discussed below
there is an example of how to set it up in the SA Controller Operator
Interfaces Technical Guide in the Supply Air Reset confi guration screens
#4 & #5 and setpoint screens #4 through #7.
If you confi gure Space Temperature or Entering Air Temperature as
the Reset Source, then separately, for the heating mode and the cooling
mode you will need to enter a Low and High Reset Source Setpoint
and a Low and High Supply Air Temperature Setpoint. This creates a
range of Reset Source Temperature Setpoints and a range of Supply Air
Temperature Setpoints. As the Reset Source Temperature varies within
its range, it will proportionally reset the Supply Air Temperature Setpoint
within its reset range. When the temperature at the Reset Source is at
the Reset Source Low Setpoint, the Supply Air Temperature Setpoint
would be reset to the Supply Air High Setpoint. When the temperature
at the Reset Source is at the Reset Source High Setpoint, the Supply Air
Temperature Setpoint would be reset to the Supply Air Low Setpoint.
When the temperature at the Reset Source is in between its Low and High
Setpoints, the Supply Air Setpoint will be proportionally reset between
its High and Low Setpoints. When the unit is in the Vent Mode or Vent
Dehumidifi cation Mode, the Supply Air Temperature Setpoint will be
calculated to be halfway between the HVAC Mode Enable Setpoints. If
Dehumidifi cation Priority has been confi gured and the unit is in Heating
Dehumidifi cation or Cooling Dehumidifi cation Mode, the Supply Air
Temperature Setpoint is proportionally reset in the same way as in the
Heating and Cooling Modes described above in this paragraph.
If the Supply Fan VFD Signal is confi gured as the Reset Source, then
separately, for the heating mode and the cooling mode, you will need
to enter a Low and High VFD Signal Setpoint and a Low and a High
Supply Air Setpoint. This creates a range of VFD Signal Setpoints and
a range of Supply Air Temperature Setpoints. As the VFD Signal varies
within its range, it will proportionally reset the Supply Air Temperature
Setpoint within its range. For example, in the Cooling Mode, when the
Supply Fan VFD Signal is at its low setpoint, the Supply Air Cooling
Setpoint will be reset to its high setpoint; when the Supply Fan VFD
signal is at its high setpoint, the Supply Air Cooling Setpoint will be
reset to its low setpoint. In the heating mode, the Supply Air Heating
Setpoint reset would react in the opposite fashion with the VFD signal at
its highest setpoint the Supply Air Heating Setpoint is reset to its highest
setpoint, and with the VFD signal at its lowest setpoint the Supply Air
Heating Setpoint is reset to its lowest setpoint. In either mode, if the
VFD signal is halfway (for instance) between the Low Signal Setpoint
and the High Signal Setpoint, the Supply Air Setpoint would be reset
to halfway between its High and Low Setpoint. If Dehumidifi cation
Priority has been confi gured and the unit is in Heating Dehumidifi ca-
tion or Cooling Dehumidifi cation Mode, the Supply Air Temperature
Setpoint is proportionally reset in the same way as in the Heating and
Cooling Modes described above in this paragraph. When the unit is in
the Vent Mode or Vent Dehumidifi cation Mode, the Supply Air Tem-
perature Setpoint will be calculated to be halfway between the HVAC
Mode Enable Setpoints.
If a Remote Reset Signal is confi gured as the Reset Source, a 0-5 or 0-10
VDC signal can be used to reset the Supply Air Temperature Setpoint.
Separately, for the Heating Mode and the Cooling Mode you will need
to enter a Low and a High Supply Air Setpoint.
As an example when using a 0-5 VDC signal, when the Reset Signal
is at 0 VDC, the Supply Air Setpoint will be at its lowest setpoint for
both Heating and Cooling. When the Reset Signal is at 5 VDC, the
Supply Air Setpoint will be at it highest setpoint for both Heating and
Cooling. As the voltage signal changes between 0 VDC and 5 VDC, the
Supply Air Setpoint will be proportionally reset between the Low and
High Supply Air Temperature Setpoint for both Heating and Cooling. If
Dehumidifi cation Priority has been confi gured and the unit is in Heating
Dehumidifi cation or Cooling Dehumidifi cation Mode, the Supply Air
Temperature Setpoint is proportionally reset in the same way as in the
Heating and Cooling Modes described above in this paragraph. When
the unit is in the Vent Mode or Vent Dehumidifi cation Mode, the Supply
Air Temperature Setpoint will be calculated to be halfway between the
HVAC Mode Enable Setpoints.
SAT Setpoint Reset