Siemens Using DXRs and Central Functions for Duct Static Pressure Reset

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DXRs and Functions for Static Pressure Reset Technologies Industry Inc Instructions of Contents and Purpose 4 Templates and Central Functions 4 4 Pressure Reset and VAV Saturation 5 5 Saturation using Central Functions 6 Saturation Level in ABT Site and ABT Inside 8 VAV Terminal with Default Values Optional 10 VAV Terminal from Saturation Calculation 13 Functions 14 Functions Basics 14 Chain Air 11 15 Used Outputs of SplyAir11 16 a Central Function 17 Central Function for Supply Air VAV Saturation Evaluation 19 Group Members and Masters 22 25 Industry Inc and Purpose document provides an overview of Duct Static Pressure Reset strategies and how to configure Central Functions to set up static pressure reset using DXR stations Static Pressure Reset is a common method for optimizing pressure in the ducts so all zones are satisfied and none are starved for air It is addressed in a number of building automation system standards and guidelines see Appendix are many ways to comply with the standards as they are intentionally vague For California Title 24 explicitly states the option of using methods to duct pressure This document provides guidance on using one method in saturation signals to manage Duct Static Pressure Reset in a simple and way This method can be used to satisfy any all of the BAS standards and for Duct Static Pressure Reset document describes how to Set up initial DXR application configuration parameters for pressure reset Set up a Central Function DXR in conjunction with the room controller Configure the use of saturation signals to control Duct Static Pressure Reset Templates and Central Functions from Hvac12 VAV and Hvac13 FPB DXR application types are used to Duct Static Pressure Reset These applications come with datapoints that can used in conjunction with AHU primary plant controllers to control and monitor the zone for reset In addition a Central Function DXR can be used to easily bridge data the zones and the AHU The DXR template applications and Central Function together allow for efficient collection of room data for use in Duct Static Pressure 24 Fault Detection for VAV and FPB Templates compliance with Title 24 an FDD configured template must be used templates are located on StdApps under Apogee Desigo ABT FaultDetection Inside new term that replaces ABT SSA Setup Service Assistant Industry Inc Pressure Reset and VAV Saturation the pressure in the duct system is too low VAV boxes may open to maximum or maximum and still not get enough air If pressure is too high boxes could be nearly and the AHU could be forcing air through them wasting energy An efficient way to these issues is to change the static pressure setpoint based on demand from zone Duct static pressure should be just low enough that a single box is almost fully At least one and preferably only one is ideal using central functions it is possible to collect data from each VAV box and use it to reset duct pressure if necessary ASHRAE recommends choosing from strategies such as flow setpoints damper position data and saturation signals document focuses on the simple and efficient saturation signal method to achieve pressure reset VAV or FPB application dynamically calculates the saturation level for the supply damper StrtnLvl Saturation level is the value used to determine if the damper is more than a set amount DlyOnStrtn Switch on delay saturation is the time delay a damper that is starving for air i e open more than a set amount initiates a change Both parameters are configurable and are under air VAV in the values task area in ABT Site any box is starved of air a signal VavSuAflStrtn SU FLO SATUR is sent to the central which then counts the total number of starved boxes The central function shares total number of starved boxes with the AHU which can then use the data to reset pressure to a level that is adequate for current demand FLO SATUR is a calculated binary object with two states 0 Satisfied 1 Starved The is true Starved when Damper position is equal to or exceeds the value of StrtnLvl Airflow error exceeds a configured error level Both conditions stay true for longer than the value of DlyOnStrtn default 90 can be adjusted to increase decrease the terminal box application to a saturation condition It can be set higher if there is concern only with boxes close to completely starved Conversely the level can be lowered if the goal is to data on boxes that are nearing saturation 90 represents a balance between the strategies The configurable time delay DlyOnStrtn default is 60 seconds This can adjusted along with the saturation level to achieve desired results Master object Group Master object in the Central Function application for supply air coordination data from supply air Group Members to support duct pressure reset When the signal the collected information being shared with the AHU fan can be used to regulate an increase to the static setpoint Industry Inc a box from the pressure reset system is possible to configure a Saturation signal in ABT Site or online to stay permanently i e This allows a user to exclude a particular terminal from the reset system This may be useful in situations where for example a certain box almost fully saturated but there is no actual need for pressure reset See for more information Saturation using Central Functions AHU control program should adjust the supply duct pressure to achieve the lowest that fully satisfies the flow setpoint at each terminal To accomplish this the AHU program collects values indicating a saturated control loop from each assigned controller air terminal controller calculates a saturation signal that indicates whether the local control loop is operating close to the limit The program in the Central Function counts the number of saturated airflow controllers among the terminals it serves and FPB applications include a saturation function that calculates and determines a configured box is operating above the configured limit The saturation function from the following objects and parameters and parameters for saturation Name FLO SATUR Supply air VAV airflow saturation 0 Satisfied 1 Starved Satisfied saturation calculation 0 No 1 Yes Yes setting level indicating that the termi

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