Orion System SA E-BUS Controller - Manual (Page 47)

SA E-BUS Controller Technical Guide
Sequence of Operations
47
For SA applications with an installed Suction Pressure Transducer, a
Head Pressure Module and a Head Pressure Transducer(s), a Defrost
Mode is available during the Heat Pump Heating operation. The SA E-
BUS Controller converts the Suction Pressure to a Suction Temperature.
A user-adjustable Suction Temperature Setpoint determines when the
unit will go into Defrost Mode during Heat Pump Heating. The unit
will operate in Defrost Mode for 10 minutes or until the Head Pressure
reaches 450 PSIG.
An Adaptive Defrost Adjustment confi guration is available that will
automatically adjust the length of the Defrost Timer (interval between
Defrost Modes) depending on if the unit stays in Defrost Mode for the
full 10 minutes or leaves the Defrost Mode early because of reaching a
Head Pressure of 450 PSIG. If Adaptive Defrost is confi gured and the
Defrost Mode is terminated because the 10 minute timer has elapsed,
this could indicate that the unit needs more defrost time. In this case,
the Adaptive Defrost Adjustment value will be subtracted from the
original Defrost Timer to shorten the interval between defrost cycles.
If the Defrost Cycle is terminated between the 8th and 9th minute, the
Defrost Timer value will not be changed. If the Defrost Cycle is termi-
nated before the 8th minute, this could indicate that the Defrost Timer
is too short. In this case the Adaptive Defrost Adjustment value will
be inversely proportionally added to the original Defrost Timer as the
termination time shortens from 8 minutes to 0 minutes.
Water Source Heat Pump Operation
For Water Source Heat Pump applications, the SA E-BUS Controller
is used in conjunction with the Water Source Heat Pump Protection
Module. Heating, Cooling, and Dehumidifi cation would operate in the
same manner as described in Air to Air Heat Pump Operation; however,
defrost operation would not apply.
The Water Source Heat Pump Protection Module provides safeties for
Proof of Flow, Low/Unsafe Suction Pressure, and Low Leaving Water
Temperature. An E-BUS Distribution Module is used to provide com-
munication from the SA E-BUS Controller to the Water Source Heat
Pump Protection Module.
For more detailed sequence and wiring information, see the AAON Tulsa
version of the Water Source Heat Pump Protection Module Technical
Guide.
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 E-BUS 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 E-BUS Controller enters the
Off Mode. During the Off Mode, the Supply Fan is off.
Supply Air Temperature Setpoint Reset
The SA E-BUS Controller incorporates a dynamic Supply Air Tempera-
ture 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 E-BUS Controller uses the HVAC Mode Enable Setpoints to
determine the mode of operation. Once the HVAC Mode has been de-
termined, the SA E-BUS 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
E-BUS 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
SAT Setpoint Reset