Room Automation Station Using DXRs And Central Functions for Supply Air Temp (SAT) Reset A6V12006922 (BA) 2021-04-15 Restricted Smart Infrastructure
Table of Contents 1 Scope and Purpose .............................................................................................................................. 4 2 DXR Templates and Central Functions .............................................................................................. 5 3 Supply Air Temperature Reset and Zone Demand ............................................................................ 6 3.1 Poor Indicators of Zone Load ............................................
Cybersecurity disclaimer Cybersecurity disclaimer Siemens provides a portfolio of products, solutions, systems and services that includes security functions that support the secure operation of plants, systems, machines and networks. In the field of Building Technologies, this includes building automation and control, fire safety, security management as well as physical security systems.
1 Scope and Purpose 1 Scope and Purpose This document provides an overview of Supply Air Temperature (SAT) Reset strategies and describes how to configure Central Functions to set up SAT reset using DXR automation stations. Supply Air Temperature Reset is a common method for optimizing supply air temperature. It is addressed in several building energy codes and system standards and guidelines - see Appendix [➙ 20]. There are many ways to comply with the standards as they are intentionally vague.
DXR Templates and Central Functions 2 2 DXR Templates and Central Functions Templates from Hvac12 (VAV) and Hvac13 (FPB) DXR application types are used to configure Supply Air Temperature Reset (SAT). These applications come with demand signals (from 0-100%) that can be used in conjunction with AHU primary plant controllers to adjust the SAT setpoint. In addition, a Central Function DXR can be used to bridge data easily between the zones and the AHU.
3 Supply Air Temperature Reset and Zone Demand Poor Indicators of Zone Load 3 Supply Air Temperature Reset and Zone Demand Keeping the Supply Air Temperature (SAT) at a constant temperature can be effective in certain situations but can also lead to wasted energy and increased costs in other scenarios.
Supply Air Temperature Reset using Central Functions Good Indicators of Zone Load 4 4 Supply Air Temperature Reset using Central Functions DXR controllers can accomplish SAT Reset using central functions by using the second strategy described above. The central function (SplyAir11) collects the number of terminals calling for cooling and heating, and determines which mode to use (Heating, Cooling, Neither, or Neutral).
4 Supply Air Temperature Reset using Central Functions Configuration 4.1 Configuration Description BACnet Name (Abbreviated Name) Type Comment Default Value Maximum Supply Air Temperature TSuMax ACnfVal Maximum allowable supply air temperature. During Heating, the SAT will not be reset above this temperature. 89.6 °F (32 °C) Start Value for Cooling SttValC ACnfVal Value at which Cooling mode would begin if the temperature was above this point. Used as Max SAT if the changeover is Neutral.
Central Functions Central Functions Basics 5 5 Central Functions 5.1 Central Functions Basics The Central Function Application or Coordinator is implemented through the use of a DXR2E/M.18 controller. Central Functions coordinate the actions of the room controller to the primary plant. A DXR running the Central Function Application facilitates group data exchange between room applications or DXRs and the primary plant controller or Field Panel.
5 Central Functions Supply Chain Air 11 The following section provides an overview on the ability and limitations of SplyAir11, the main Central Function used for Supply Air Terminal Reset. For information on other central functions, see ABT Site Help. 5.2 Supply Chain Air 11 The application function “Supply chain air 11” (SplyAir11) collects the demand signals of the different rooms via group mechanism and provides the setpoint and demand for the central air handling unit.
Central Functions Supply Chain Air 11 5 For SAT Reset, there are two lower level functions that are used to control the setpoints. These are Supply Changeover for Air (SplyChovrAir11) and Supply Temperature Setpoint (SplySpTSu11). SplyChovrAir11 reads the Changeover conditions (Heating, Cooling, Neither, Neutral) from all the terminals and determines what the Changeover mode should be for the AHU based on the terminals. For this calculation, it is simply the larger number that will win.
5 Central Functions Supply Chain Air 11 Commonly Used Outputs of SplyAir11 Description BACnet Name (Abbreviated Name) Type Comment Command for changeover mode air ChoAirModCmd MPrcVal Multistate value that deter- To Terminals mines the changeover condition (Heating, Cooling, Neither, Neutral). (CHVR M AIR) Note: Must select “Changeover condition determin. for air” = ACTIVE in ABTSite Central Function configuration.
Central Functions Adding a Central Function 5 5.3 Adding a Central Function 1. Choose the Building component. 2. Choose the Building Structure task. 3. Choose the Add application template button from the Add Device drop-down. 1. 2. 3. 4. Choose the Types in Library tab. Choose the CentFnct11_A type. Select the AS Type required. Choose the Add template to project button. 1. Click the Template Properties button.
5 Central Functions Adding a Central Function 1. Click the “More” button. 1. Enter an Application Number. 2. Click OK.
Central Functions 5 Configuring Central Function for Supply Air Temperature Setpoint Evaluation 5.4 Configuring Central Function for Supply Air Temperature Setpoint Evaluation 1. Choose the Central HVAC Function. 2. Choose Supply chain for air. 3. Click the drop down, and change None to Supply chain air 11, for central AHU. (Note that selections for Setpoint for supply air temp determ. and Changeover condition determ.for.air are changed to active with that selection.
5 Central Functions Configuring Central Function for Supply Air Temperature Setpoint Evaluation 1. The selected set of default value for theSupply chain air for Setpoint for supply air temperature determination are displaced in the left window 2. Change the default values so they are consistent with energy code recommendations for the VAV System. For example, Cooling should be from 50 °F to 65 °F. 3. Close the application. 4. Add the Central Function device to the building hierarchy. 1.
Central Functions Configuring Central Function for Supply Air Temperature Setpoint Evaluation 5 1. Change the Infrastructure Priority Object. NOTICE! When configuring a Central Function app type for the first time, the Infrastructure Priority Objects must be changed. If they are kept as defaults, they can cause alarms to come in at a Life Safety priority, regardless of the actual status. Settings should be as shown above. 2. Close the application. 3.
5 Central Functions Configuring Group Members and Masters 5.5 Configuring Group Members and Masters Group master/member communication is how all central functions read and write to other applications. The high-level central function controls a single Group Master object. This Master object is then what writes to the Group Member objects in the lower level application functions.
Central Functions Configuring Group Members and Masters 5 1. Expand the Central function. Modify the Group Number to 1 (It may already be set to 1). 1. With the Group Master selected, the VAV Automation Stations should display in the Group Members tab. NOTICE! All Automation Stations used in the Supply Air Temperature Reset calculations must have an Assigned selection in this tab. Note: All Central Functions can be grouped hierarchically, which is used for separating Group Member and Master functions.
6 Appendix 6 Appendix ASHRAE 90.1-2019 6.5.3.2.3 Supply air temperature reset controls. IECC -2017 C403.6.5 Supply air temperature reset controls California Title 24 -2019 140.4(f) Supply Air Temperature Reset Controls 140.4(d)2iii 20 | 21 Multiple zone HVAC systems must include controls that automatically reset the supply air temperature in response to representative building loads or to outside air temperature.
Issued by Siemens Industry, Inc. Smart Infrastructure 1000 Deerfield Pkwy Buffalo Grove IL 60089 +1 847-215-1000 A6V12006922 (BA) © Siemens Industry, Inc., 2021 Technical specifications and availability subject to change without notice.
