Orion System RNE Modular Controller - Manual (Page 63)

RNE Modular Controller Field Technical Guide
SEQUENCE OF OPERATION
63
Building Pressure Control and CAV/MUA Dual Mode
If the Static Pressure ever rises 0.5” above the Duct Static Pressure
Setpoint, the Duct Static Pressure Control Output Signal will be cut
in half every control period until the Static Pressure is brought under
control. This is to prevent damage to the ductwork if all the VAV
boxes are closed or some other blockage occurs in the ductwork.
WARNING: The manufacturer does not assume responsibility
for protecting the equipment from over-pressurization! You should
always install mechanical high static protection cutoffs to protect
your system!
Any time the Supply Fan is off, the Duct Static Pressure Control Output
Signal will remain at zero volts. If the Supply Fan control is not con-
fi gured for Duct Static Pressure Control, you can still monitor the Duct
Static Pressure if the Duct Static Pressure Sensor is installed; however,
no control will occur.
Duct Static Pressure Control for
Filter Loading
In order to maintain a constant CFM through the supply air ducts on a
mixed air CAV unit, the RNE can utilize a Duct Static Pressure Sensor
(used to monitor the discharge pressure) in conjunction with a Supply
Fan VFD. If the fi lters are getting dirty, the VCM will ramp up the VFD
to compensate for the decrease in airfl ow. To utilize this feature, the
unit must be confi gured to use VFD Fan Control. This feature cannot
be used if this is a VAV or Zoning application with typical Duct Static
Pressure Control.
Building Pressure Control
The RNE can maintain Building Static Pressure any time the Supply
Fan is operating by activating a Constant Volume Exhaust Fan, a VFD
Exhaust Fan, or Modulating Exhaust Damper, or by modulating the
Outdoor Air Damper. A Building Pressure Transducer must be connected
to the VCM-X’s Expansion Module. For Constant Volume Exhaust
Fan applications, only an Exhaust Fan Relay needs to be confi gured
for on/off operation of the Exhaust Fan. VFD or Modulating Building
Pressure control must be confi gured in order for this feature to operate.
An Exhaust Fan Relay can also be confi gured along with Modulating
Building Pressure control for an Enable output. Building Pressure can
be maintained by either Direct or Reverse Acting control.
Direct Acting Modulating Control
If confi gured, a VFD Exhaust Fan or Modulating Exhaust Damper will
be controlled by varying a 0-10 or 2-10 VDC control signal. If an en-
able output is required, an Exhaust Fan Relay can also be confi gured.
The Exhaust Fan Relay and the Modulating Signal will activate when
the Building Static Pressure rises above the Building Static Pressure
Setpoint plus the Deadband. The Exhaust Fan Relay will remain active
until the Building Static Pressure falls below the Building Static Pressure
Setpoint minus the Deadband and the Modulating Signal falls to 0%.
Direct Acting On/Off Control
If you do not require a Modulating Control Signal, you can also confi gure
one of the Relay Outputs as an Exhaust Fan Relay to activate whenever
the Building Static Pressure is above the Building Static Pressure Set-
point plus the Deadband. The Exhaust Fan Relay will deactivate when the
Building Static Pressure falls below the Building Static Pressure Setpoint
minus the Deadband. Only one Relay Output should be confi gured for
this operation. There is no staging of additional Exhaust Fan Relays.
Reverse Acting Modulating Control
If confi gured, on a drop-in building static pressure below the building
pressure setpoint minus the deadband, a 2-10 VDC signal will modu-
late to open the outside air damper. When this option is selected, no
economizer-free cooling or IAQ operation will be available.
CAV/MUA Dual Mode ( Hood On/Off
Operation)
The RNE Controller can be confi gured as a CAV controller but switch
to MUA operation when an exhaust hood is energized. This MUA force
mode occurs when a 24 VOut wet contact closure is received on the
Hood On binary input on a RNE Controller Expansion Module. Under
normal operation (CAV), the unit will operate as a recirculating space
temperature (and space humidity) controlled unit. When the Hood On
contact is made, the unit will open the Outdoor Air Damper to its full
open position. The Heating and Cooling Modes will then be determined
by the Outdoor Air Temperature Sensor using the same Heating and
Cooling Setpoints that were used in the CAV mode. Dehumidifi cation
would then be initiated by an Outdoor Dewpoint Setpoint. When the
Hood On Force Mode is removed, the unit will revert to CAV operation
with the Outdoor Damper returning to its minimum position (unless
economizer operation is enabled) and with mode control initiated by
the Space Temperature and Humidity Sensors.
MUA Unoccupied Operation
Normally, an MUA unit is off during the Unoccupied Mode. However, if
the unit has Return Air, it can be confi gured to operate as a recirculating
Night Setback Controlled unit during Unoccupied Hours. This is ac-
complished by simply confi guring Night Setback Temperature Setpoints
(anything other than the default 30ºF) on a unit that is also confi gured for
Outdoor Temperature Control (MUA). With this confi guration, when the
unit goes Unoccupied, it will close the Outdoor Air Damper and begin
to use a Space Temperature Sensor in conjunction with the existing
Heating and Cooling Setpoints, offset by the Night Setbacks, to make
Night Setback calls. If a Space Humidity Sensor is installed, and the
unit is confi gured for Night Humidity control, the RNE Controller will
use the Space Humidity Setpoint for unoccupied Dehumidifi cation calls.