DDCSequencingand# Redundancy# - ASHRAE · • Serieswaterside(economizer •...

DDC Sequencing and Redundancy

Presenter

•  Importance of sequencing •  Essen%al piece to designing and delivering a successful project •  Defines how disparate components interact to make up a ‘system’

•  The fundamentals to sequencing •  Mechanical designers intent •  How it should operate •  How to control to meet both

•  Simplicity is key •  Clear, concise and complete

•  Overview of process •  Analyze mechanical design •  Outline SOO •  Fill in details •  Op%mize system

Sequencing

•  Systema@c approach to developing SOO’s. •  Map out en%re system, compartmentalize components if possible,

analyze system on a component level •  Define instrumenta%on on a component level •  Develop I/O list for components including hardwired points and data

connec%ons •  Define Instrumenta%on on the system level •  Develop I/O list for system •  Iden%fy set points, alarms, schedules and trends

Sequencing

•  Series water-‐side economizer

•  Primary-‐secondary chilled water pumping

•  Variable speed condenser water pumping

•  Dual piping loops

Example System – Chilled Water Plant

•  Systema%c approach to developing SOO’s. •  Map out en@re system, compartmentalize components if possible,



Sequencing

•  Define system by it’s disparate components

•  N+1 component redundancy

•  One-‐to-‐one rela%onships

Map Out En@re System

Compartmentalized Components

•  Compartmentalize system as best as possible.

•  Create “Line-‐ups” of equipment

Chiller Plant System – Component Level

•  Break down system to the individual component level

•  Systema%c approach to developing SOO’s. •  Map out en%re system, compartmentalize components if possible,

analyze system on a component level •  Define instrumenta@on on a component level •  Develop I/O list for components including hardwired points and data


Sequencing

Component Level – Defining Instrumenta@on

•  As laid out by the mechanical designer

•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable


•  Unit Mounted Controller




•  Shut-‐off/Isola%on Valves



•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control






•  Temperature Sensor

•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control





•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control •  Opera%ng Restraints




•  Head Pressure Control


•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control •  Opera%ng Restraints






•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control •  Opera%ng Restraints •  Op%miza%on





•  Addi%onal Sensors


•  What instrumenta%on is required to meet intent and opera%on? •  Enable/Disable •  Capacity Control •  Opera%ng Restraints •  Op%miza%on



connec@ons •  Define Instrumenta%on on the system level •  Develop I/O list for system •  Iden%fy set points, alarms, schedules and trends

Sequencing

Develop I/O List for Components

Repeat instrumenta@on and I/O for other components

•  Cooling Tower

•  Condenser Water Pump

•  Primary Chilled Water Pump

•  Secondary Chilled Water Pump



connec%ons •  Define Instrumenta@on on the system level •  Develop I/O list for system •  Iden%fy set points, alarms, schedules and trends

Sequencing

•  How do the disparate components interact with the system?

System Level – Defining Instrumenta@on

•  System Valves



•  Flow Meters



•  Flow Meters

•  System Temp Sensors



•  Flow Meters


•  Differen%al Pressure Sensors




connec%ons •  Define instrumenta%on on the system level •  Develop I/O list for system •  Iden%fy set points, alarms, schedules and trends

Sequencing

Develop I/O List for System



connec%ons •  Define instrumenta%on on the system level •  Develop I/O list for system •  Iden@fy set points, alarms, schedules and trends

Sequencing

•  Avoid exact set points, baselines are recommended •  Typically done by Cx agent along with the balancing contractor

•  Define schedules

•  Alarms can be addressed as virtual points in points list as well as safe%es that typically take the form of hardware

•  Define trends

Iden@fy Set Points, schedules, alarms, trends

•  Understand the importance of sequencing

•  Become in%mate with the fundamentals of the design

•  Define your systema%c approach to developing sequences

•  Keep it simple!

Sequencing

Ques@ons?

•  Where and why redundancy in DDC is required

•  Redundant systems within a facility

•  DDC System Redundancies

•  Redundant Instrumenta%on •  Redundancy in system architecture •  Physical separa%on of installed control components •  Dual power supplies with separate feeds to each control panel •  Network Redundancy •  Separate supervisory networks •  Redundant Servers

•  PLC Systems

Redundancy in DDC

•  Where:

•  Mission Cri%cal Facili%es (MCF)

•  What it means to be a ‘Mission Cri%cal’ •  Facili%es that require 100% up%me 24 hours a day 7 days a week for

normal business opera%on

•  Redundancy provides maximum reliability but also generates maximum cost and complexity

•  Examples: Data Centers, Hospitals, Laboratories

Redundancy in DDC

•  Why:

•  Enables con%nuous opera%on during cri%cal system failures

•  Meets owner’s requirements for minimized down%me •  Designing for redundancy in all building systems, including the DDC

system may be required

•  Site-‐wide control coordina%on •  Example coordina%on types: Temperature Control , Power restart,

Load Shedding, Humidity Control, Pressuriza%on

Redundancy in DDC

Redundant Systems

•  N+1 component redundancy

•  Dual piping loops

Redundant Systems

•  DDC system redundancy isn’t addressed by Up%me

•  Redundant mechanical equipment s%ll needs DDC to func%on properly

•  Fault Tolerant Control Systems – any single controller or communica%on network

•  Redundancy in DDC is necessary to ensure any malfunc%on or loss of power within the control system will not affect cri%cal equipment opera%on

Redundant Systems

•  Redundant Instrumenta@on

•  Redundancy in system architecture

•  Physical separa%on of installed control components

•  Dual power supplies with separate feeds to each control panel

•  Network Redundancy

•  Separate supervisory networks

•  Redundant Servers

DDC System Redundancies


•  Flow Meters


•  Differen%al Pressure Sensors

Redundant Instrumenta@on

•  Redundant Instrumenta%on








Redundancy in System Architecture

•  DDC system architecture depends on the make-‐up of the mechanical and electrical systems

•  DDC system architecture designs to achieve redundancy:

•  Primary-‐Redundant Managers (True Primary/Redundant) •  Distributed Control (Line-‐Up Configura%on) •  Hybrid (Line-‐Up Configura%on with PR Managers)

•  How to find the right design for your applica%on

•  Compartmentalize the systems as best as possible


•  Primary-‐Redundant Managers (True Primary/Redundant)


•  Distributed Control (Line-‐Up Configura%on)


•  Hybrid (Line-‐Up Configura%on with PR Managers)



•  Physical separa@on of installed control components






Physical Separa@on of Components

•  DDC Controllers

•  Variable Frequency Drives

•  Redundant Sensors

•  Control Valves

•  Wiring




•  Power redundancy





Power Redundancy

•  Control panels need to be powered at all %mes to properly func%on

•  Examples: •  UPS power from two sources with a local ATS •  UPS power from electrical system with back-‐up generator and local UPS

Network Redundancy

•  Concept of ‘self-‐healing’ communica%on busses

•  Redundant topologies (network’s virtual shape or structure)

•  Ethernet Topologies •  Bus Topology •  Classic Star Topology •  Tree Topology (combina%on of bus and star) •  Ring Topology

•  Redundancy through ring topology is becoming the most popular for the BMS market

•  Wireless Mesh

Network Redundancy

•  Bus Topology •  Uses a common backbone to connect all devices. Failure of one node or

link affects the rest of network •  Works best with a limited number of devices due to the broadcast traffic

it generates

Network Redundancy

•  Star Topology •  Most common network setup •  If the central hub fails, all devices connected to that hub would be

disconnected •  Performance of the network is dependent on the capacity of central hub

(router or switch)

Network Redundancy

•  Tree Topology •  Integrates mul%ple star topologies together onto a bus. •  This hybrid approach supports future expandability of the network much

beier than a bus

Network Redundancy

•  Ring Topology – N+1 •  U%lizing industrial switches •  Redundant rings is becoming the most popular for the BMS market •  Ethernet rings will cause broadcast storms and can ul%mately cause the

network to stop working •  How to fix this? -‐ Spanning Tree Protocol

Network Redundancy

•  Spanning Tree Protocol (STP)

•  Although two cable paths exist, messages can only travel in one direc%on

•  STP solves problems in a ring topology including broadcast storms

•  STP does for an Ethernet network what a router does for an IP network

•  Typically provides network recovery %mes of 30-‐60 seconds

•  Rapid Spanning Tree Protocol (RSTP)

•  Provides faster spanning tree convergence aler a topology change

Network Redundancy

•  Wireless Mesh Topology •  Can take any of several possible paths from source to des%na%on. •  Devices are connected with many redundant interconnec%ons between

network nodes •  In a true mesh topology every node has a connec%on to every other node

in the network.

Network Redundancy

•  The most common problems in any fieldbus or high speed digital communica%ons system are:

•  Cabling and wiring faults: •  Reflec%ons, interference, cable rou%ng and grounding faults etc.

•  Poor design and installa%on: •  Lack of awareness of avoidable issues at design stage, poor rou%ng,

layout, untrained installers, inaccurate or insufficient system documenta%on

•  Device and wiring failures: •  Rare but can lead to communica%ons faults or peripheral faults

Separate Supervisory Networks

•  SNMP monitoring on equipment back to a separate owner network and server

•  Other secondary monitoring methods such as web based services

Redundant Servers

•  Servers are also at risk for being a single point of failure

•  Server redundancy minimizes down%me caused by:

•  Planned Maintenance •  Hardware Failure

•  Redundancy Methods

•  Two separate servers –passive synchroniza%on rou%ne •  Two separate servers – with an ac%ve synchroniza%on rou%ne •  Clustering and/or VM’s (Virtual Machines)

Redundant Servers

•  Two separate servers – would have some manual back up and a passive synchroniza%on rou%ne

•  Two separate servers – with an ac%ve synchroniza%on rou%ne

•  Two computers using separate network between them that buffers and replicates the data going into one machine

•  Poten%ally lose the buffer as data is being passed between the two.

Redundant Servers

•  Clustering and/or VM’s (Virtual Machines)

•  Two different things but from controls perspec%ve doesn’t maier

•  Server Clustering – combining two or more servers that are interconnected to appear as one

•  Load balanced clustering/fail over clustering

•  Need clustering solware that monitors the ac%ve nodes in a server cluster and transi%ons a failed server’s workload to the secondary node

•  Virtual Machines – maintain an exact mirror copy on a second physical server

PLC Systems

•  PLC systems are more robust, have higher performance, faster networks and more flexible programming capability

•  PLC’s have the capability to have Hot Standby Processors (no PID tuning required): the scans of the primary and standby controllers are synchronized

•  Redundant Power Supplies – separate power supplies can be provided for PLC controllers.

•  Redundant Networks

•  Difference in costs between PLC and DDC control -‐ up to 5:1 cost

•  Where and why redundancy in DDC is required

•  Redundant systems within a facility

•  DDC System Redundancies

•  Redundant Instrumenta%on •  Redundancy in system architecture •  Physical separa%on of installed control components •  Dual power supplies with separate feeds to each control panel •  Network Redundancy •  Separate supervisory networks •  Redundant Servers

•  PLC Systems

Redundancy in DDC

Ques@ons?

DDCSequencingand# Redundancy# - ASHRAE · • Serieswaterside(economizer •...

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