Orion System VCM-X Modular E-BUS - Manual (Page 60)

Zone
Zone
SEQUENCE OF OPERATIONS
VCM-X Modular E-BUS Controller Technical Guide 60
Remote Control of HVAC Mode
NOTE: When using the Remote Control of HVAC Mode, both of the
Heating and Cooling HVAC Mode Enable Setpoints must be set to 1
and the Mode Enable Sensor must be set as Supply Air Temperature.
The Heating Mode, Cooling Mode, and Vent Mode can be determined
by a remote Building Automation System ( BAS). The VCM-X E-BUS
will check the VCM-X Expansion Module for a 24 VAC input signal
on BI5 and BI6. BI5 is used for Remote Forced Heating Mode. BI6 is
used for Remote Forced Cooling Mode. If a 24 VAC signal is present on
both BI5 and BI6, the VCM-X E-BUS will be in Remote Forced Vent-
ing Mode. Remote Forced Venting Mode is considered to be Occupied
Fan-Only operation. Once the Remote Forced Mode has been set, normal
Heating, Cooling, or Venting Modes of operations will occur. All other
user-adjustable setpoints, such as the Heating and Cooling Supply Air
Temperature Setpoints, are used in the actual control of the equipment.
During Dehumidifi cation, if a Reset Source is not confi gured, the Supply
Air Temperature Setpoint will be 70°F.
The Remote Occupied Input on the VCM-X Expansion Module, BI4,
can also be used for Occupied Fan Only operation when the Remote
Forced Heating or Cooling inputs are not activated.
Supply Air Temperature Setpoint Reset
The VCM-X E-BUS Controller incorporates a dynamic Supply Air Tem-
perature Reset function based on a selected Reset Source. The available
Reset Source options are Space Temperature, Return Air Temperature,
Outdoor 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 VCM-X E-BUS uses the HVAC Mode
Enable Setpoints to determine the mode of operation. Once the HVAC
Mode has been determined, the VCM-X E-BUS 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 VCM-X / RNE Controller Operator Interfaces
SD Technical Guide in the Supply Air Reset confi guration screens #4
& #5 and setpoint screens #4 through #7.
If you confi gure Space Temperature, Return Air Temperature, or Outdoor
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 Tempera-
ture 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 pro-
portionally 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
(set jumper to 0-10V). Separately, for the Heating Mode and the Cool-
ing 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.
Remote Control of HVAC Mode & Supply Air Control