### Performing ZN line test and balance in the WebCTRL® interface You can use the WebCTRL® interface to calibrate a ZN line controller’s flow sensor during test and balance. Each VAV terminal unit (VAV box) must be controlled by a control program that uses an Airflow Control microblock. Control programs for dual duct boxes require 2 Airflow Control microblocks. Follow the process below to perform test and balance on one or more VAV boxes.
Click for details below Step 1: Define airflow source rules Step 2: Set initial values Step 3: Calibrate the zero flow point (Auto Zero) Step 4: Calibrate each VAV box
#### Step 1: Define airflow source rules NOTE This step is typically done by the controls engineer that designed the system. If you used SiteBuilder’s default source rules when you created the heat and cool source trees and you named the BACnet Analog Input microblock and the Airflow Control microblock to agree with the source rules, go to Step 2: Set initial values. If you used a different naming convention, you must add new source rules to SiteBuilder’s source trees to define the relationship between equipment. The relationship allows the WebCTRL® test and balance tool to find the air sources. NOTE Do not delete the default source rules. Any standard Automated Logic® control programs would no longer function correctly if these were deleted. To add new source rules: In SiteBuilder, select a source tab in the right pane. Double-click the system to open the System dialog box. Select the Source Rules tab. Click Add. In the Parent Microblock Reference Name field, type the reference name of the static pressure BACnet Analog Input microblock in the parent air source. In the Child Microblock Reference Name field, type the reference name of the Airflow Control microblocks. In the Data Target Microblock type column, select T&B Airflow. Click OK. Repeat steps 4–7 to add more source tree rules. You must add a rule for each parent/child reference name combination found in the tree. Click OK. NOTE If you change the BACnet device instance number of any parent in a source tree, right-click the source tree in SiteBuilder and select Reapply Source Tree Rules.
#### Step 2: Set initial values NOTE This step is typically done by the controls engineer that designed the system and then verified by the Test and Balance technician. The test and balance procedure calibrates the airflow sensor by comparing raw sensor readings to measured air flows at different flow rates (damper positions). Follow the steps below to set up initial values for each airflow microblock. On the WebCTRL® Geographic tree, right-click the area or equipment that you want to set up, then select Airflow Config. NOTE To set up your entire system, right-click the system level, then select Airflow Config. Change the desired design properties.
#### Step 3: Calibrate the zero flow point (Auto Zero) NOTE This step is done by the Test and Balance technician. Use the following steps to calibrate the zero flow point. To prevent damage to equipment, ensure that the parent air source is turned off. On the WebCTRL® Geographic tree, select the flow control point under the piece of equipment that you want to test and balance. Click the Properties page Details tab. Click Global Damper Commands under Test and Balance. Select the airflow dampers (microblocks) you want to set. Use Ctrl+click, Shift+click, or both to select multiple items. Click Zero Flow. Wait for the Message column to show that Auto Zero is complete. After Auto Zero is complete, use other global commands to set the VAV boxes to another mode to prepare the system for flow calibration. There are many different ways to do this, and it is up to the test and balance technician to decide how to operate the system while calibrations are performed. The goal is to have a system at a steady static pressure that is near the design operating conditions. The air source should not be restarted until the VAV boxes have been commanded to a state where some dampers are open. Some suggested modes are: Set all VAV boxes to control to the occupied minimum setpoint. Set a subset of VAV boxes to damper full open and the remaining VAV boxes to damper closed. Set all VAV boxes to automatic control. After all selected dampers have been set to Auto Zero, close the Global Damper Commands dialog box.
#### Step 4: Calibrate each VAV box NOTE This step is done by the Test and Balance technician. After the air source and associated VAV boxes are controlling to the state determined above, calibrate each VAV box. You must calibrate each VAV box at Zero Flow and Cool Max Airflow or Heat Max Airflow. For improved accuracy, calibrate additional points such as Dampers Full Open and Occupied Min Airflow. When calibrating additional points, follow the numeric order shown under Damper command. NOTE Some systems cannot maintain design static pressure until test and balance is performed. To raise the air source's static pressure, close some VAV dampers or have them control to the occupied minimum setpoint. On the WebCTRL® Geographic tree, select the flow control point under the piece of equipment that you want to test and balance. Click the Properties page Details tab. Under Test and Balance, click the damper position you want to calibrate. Wait for the damper to quit moving as indicated by the status message on the Properties page. Measure the airflow from the VAV box that you are calibrating. Under the Test and Balance section, type the measurement into the Measured Flow field next to the damper command. Click the arrow to copy the current reading, or type the raw sensor reading. Click Accept. To calibrate additional points, repeat steps 1 through 6 for each calibration point. When the desired calibration points are complete, return the VAV box to the mode it was in previously until you finish calibrating all VAV boxes. After you calibrate all the VAV boxes, return all the VAV boxes to Automatic Control using the Global Damper Commands button. NOTE If you leave a VAV box in any test and balance mode other than Automatic Control for more than 12 hours without any additional calibration activity, the VAV box resumes automatic control.