3 Minute Read

| Overview

A Bypass Damper is an additional damper used in the zones, to relieve the excess pressure on a single-stage fan. A SmartNode is used to control the damper, and a differential pressure sensor is used to provide the inputs for the control outputs. The Generic PI loop under the profiles of 75F BMS provides the control sequences for the setup.

| How it works

The PI Loop Control terminal profile can be used for a wide range of applications. Using an input to reset or modulate an output.  In this case, the pressure inputs from the differential pressure sensors are used to modulate the bypass damper, relieving the excess pressure on the fan.

| Installation


The Bypass Damper setup comes with the following as a package:


  • Bypass Damper (of required size)
  • Belimo Actuator (pre-mounted on the damper)
  • Bracket to install the SmartNode( pre-mounted on the damper)
  • Differential pressure Sensor (DLP ACI)
  • Black poly tubing (25 feet)
  • Pitot tube
  • SmartNode (with Allen screws to mount)

Installing the Bypass Damper setup requires the following tools and devices


  • Drilling Machine/Impactor
  • 1/2 inch/ smaller drill bit
  • Control set screwdriver
  • Allen wrenches

The installation of the Bypass Damper Setup involves the following steps:

  • Mounting the Bypass Damper:
    • Mount the Bypass damper setup onto the ductwork (in the location specified for the bypass damper) driving 3 or more tech screws.


Note: Maintain a good distance from the static damper while installing, to avoid the collision of the plates in the Bypass and static dampers.

  • Mounting the SmartNode:
    • Mount the SmartNode on the bracket provide on the damper.
    • Fasten the Allen screws using the Allen wrenches set to confirm a firm mounting. 


  • Mounting the Differential Pressure Sensor:
    • Mount the Differential pressure sensor as close to the StartNode as possible (to ease the troubleshooting, and diagnosis, and to resolve any power and connection issues).
    • Use two screws to mount it firmly outside of the duct or anywhere close to the controller.
    • Make sure the dip switches are in the proper positions
      • The big blue switch towards V out to sync with the type of signal used.
      • The other switches to the right, to set as 0–1-inch water columns and Unidirectional for the bypass damper.
  • Mounting the Pitot Tube:
    • Run the 25 feet poly tubing down the supply duct
    • Drill a hole in the ductwork.
    • Push the pitot tube through the drilled hole (make sure the airflow is along the direction of the arrow in the pitot tube)
    • Squeeze the tubing to the pitot tube.
    • Squeeze the tubing to the high-pressure port, on the differential pressure end. 

| Wiring


  • Wire the Analog out and the 24-volt power supply from the SmartNode to the bypass damper actuator.
  • Wire the input from the Differential Pressure Sensor to the Analog in of the SmartNode, and the common 24-volt power supply from the SmartNode to power the Differential Pressure Sensor.

| Configuration

The Bypass damper uses the Generic PI loop profile from the CCU for the control sequences. To configure a generic PI loop profile,

From the CCU Zones page,


  • Click the settings mceclip2.png icon.

The floor layout screen is displayed.


  • Click Add Zone+ to add a new zone for the bypass damper installation and enter a zone name.


  • Click Pair Module+ to pair the bypass damper module.

The select device type screen is displayed.


  • Click SN to pair a SmartNode.

The select module type screen is displayed.


  • Click the PI Loop Controller profile.


  • Follow the instructions in the pairing steps screen to pair the SmartNode. using the pin generated at the SmartNode.

The PI Loop Controller configuration screen is displayed.


| Configuration Parameters

Select the parameters as shown below.




  • Differential Pressure Sensor (0.0.25) in H2O under the Analog-in1 Input Sensor, which sets the predefined Target Value and the Expected Error Range
  • Set the analog out values for the modulating outputs for the damper based on the sequences.

The target Value is your set point. Set this value to the desired target value. (e.g.) the pressure target value maybe 0.5"w.c.)

The Expected Error Range + Target Value is when you will reach the maximum loop output.

Analog-out1 at Min Output -The minimum output on AO1. If you are at or below the setpoint, your output will be at this value. 

Analog-out1 at Max Output -The maximum output on AO1. If you are at or above the Target Value + Expected Error Range. If you are above your maximum expected error range, then your AO1 will go to this value. 

Once the required parameters are set.

  • Click Set to confirm the parameters.

Once confirmed the profile starts to control the Bypass damper setup as below, using the set parameters.




| Failsafe Mode

When the SmartNode loses the connection with the CCU, all the PI loop controls and safety checks (if any), are handled by the smartnode itself.




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