Orion System RNE Modular Controller - Manual (Page 61)

RNE Modular Controller Field Technical Guide
SEQUENCE OF OPERATION
61
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 RNE Controller enters the Off
Mode. During the Off Mode, the Supply Fan is off and the Outdoor Air
Dampers are closed.
Head Pressure Control
If Head Pressure Control is being utilized, the Two Condenser Head
Pressure Module will be used, and each compressor will have a cor-
responding condenser fan or water valve. Units with two compressors
will use (1) Two Condenser Head Pressure Module. Units with four
compressor will use (2) Two Condenser Head Pressure Modules. The
condenser outputs will be controlled to maintain that circuit’s Head
Pressure Setpoint.
Cooling/Dehumidifi cation Mode
When a compressor is called to run (for either Cooling or Dehumidifi ca-
tion), the corresponding Condenser Enable Relay will be energized to
enable the Condenser Fan or Water Valve. In a water cooled system,
the signal to the water valve will start at 75% for 3 minutes. In an air
cooled system, the signal to the condenser fan will start at 50% for 30
seconds. The condenser signal will then modulate between 0 and 100%
to maintain the appropriate Head Pressure Setpoint. Both a Cooling
and a Dehumidifi cation Head Pressure Setpoint can be confi gured. The
output signal to a water valve can be confi gured as 0-10 VDC or 2-10
VDC. The output to the ECM motor of a condenser fan is a 0-100%
PWM signal. Both outputs mirror each other.
Heat Pump Mode
In the Heating Mode, the RNE Controller will communicate to the Two
Condenser Head Pressure Module that Heating is enabled. The Heat-
ing Enable Relay(s) will energize, and the condenser output signal will
go to 100% and remain there until the Heat Enable signal is removed.
NOTE: The Heating Enable Relay(s) outputs are for indication
only and are not wired to anything.
NOTE: For other details specifi c to confi guration and trouble-
shooting of the Two Condenser Head Pressure Module,
see the Troubleshooting Section on page 82.
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 RNE 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 RNE will be in Remote Forced Venting 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 Vent-
ing 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 RNE Controller incorporates a dynamic Supply Air Temperature
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 RNE uses the HVAC Mode Enable
Setpoints to determine the mode of operation. Once the HVAC Mode
has been determined, the RNE 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
RNE 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, 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
Temperature varies within its range, it will proportionally reset the Sup-
ply Air Temperature Setpoint within its reset range.
Head Pressure Control and Remote Control and SAT Setpoint Reset