Building Automation System Interfacing to a VAV System
Building Automation System • Interfacing to a VAV System • A BAS monitors inputs... • Analog • Return air temperature • Off-coil temperature • Duct static pressure • Binary • Filter clean/dirty status • Fan hand/off/auto status • Fan alarm • Fan status
Building Automation System • Interfacing to a VAV System • ... and controls outputs • Analog • Cooling coil valve position adjust • VSD setpoint adjust • Binary • Return air dampers control • Fan start/stop control
Building Automation System CP VSD Points in Control Panel Fan Speed Control Trip Alarm Auto/Manual Status Fan Start/Stop Control AI BO BI AO AI AO BI BI BO BI AI
Building Automation System • Return Air Temperature • Uses a bulb-type sensor. • Measures temperature of air returning from space through ceiling plenum. • Typically 28°C to 30°C due to heat load and heat gain in plenum from lights. • Indication of average space temperature
Building Automation System • Return Air Damper Control • Only used when VAV AHU is used for pressurization during fire mode. • Normally, damper is full open to allow return air to mix with fresh air. • In fire mode, damper shuts so AHU pressurizes space to assist smoke spill system and control movement of smoke
Building Automation System • Filter Alarm • Switch which closes when differential pressure across filter exceeds a certain value. • As filter gets dirty, it clogs up and differential pressure increases. • When the switch closes the operator is advised to replace the filter.
Building Automation System • Cooling Coil Control • Chilled water valve is controlled to maintain off-coil temperature setpoint. • Actuator can take one of following signals: • Digital communication bus • 0-10 VDC • 4-20 mA
Building Automation System • Off Coil Temperature • Uses averaging sensor to measures air temperature after cooling coil. • Used to control cooling coil to achieve an off coil setpoint of 10°C to 14°C. • Bulb type supply air temperature sensor sometimes used in place of off coil temperature.
Building Automation System • Fan Speed Control • Signal from BAS changes setpoint of Variable Speed Drive controller. • Signal from BAS is either 0-10 VDC or4-20 mA • Variable Speed Drive controller sends appropriate signals to fan.
Building Automation System • Trip Alarm • Voltage-free contact closes when fan motor trips due to: • Motor overload • VSD overload • When trip alarm occurs, operator is alerted and advised to investigate.
Building Automation System • Auto / Manual Switch • If somebody has taken control away from the BAS by changing the Hand/Off/Auto switch away from Auto position, the operator is advised. • If switch is Manual position, operator knows that he has no control over the fan.
Building Automation System • Fan Start/Stop Control • Applies 24VAC signal to control panel. • VSD manages timing associated withsoft-start of fan.
Building Automation System • Fan Status • Uses differential pressure switch to give positive feedback of fan operation.
Building Automation System • Static Pressure • Controlled by pressure control loop to achieve a setpoint.
Building Automation System Hardware Elements
Building Automation System DDCController • One AHU per controller for fault tolerance • Stand-alone DDC control program stored in E2PROM • Each analog input can also be configured to monitor two binary inputs • Default time schedule for stand-alone operation • No battery
Building Automation System N2 Bus • Communication network between DDC controllers and Network Control Unit • 3 wires, RS-485, 1500 feet • Sends start/stop and adjust commands from NCU to DDC controllers • Reports all binary change of states to NCU • Reports analog values when requested by NCU
Building Automation System NetworkControl Unit • Provides BAS features for associated DDC controllers • Fault tolerance - no single point of failure • System performance independent of size • “PC in a box” • 80386 processor • Up to 10 Meg SIMM • 2 ISA slots
Building Automation System NetworkControl Unit • Connection points for: • Network Terminal • Notebook PC • Printer • Modem • 72 hour battery backup of programs and data • Real-time multi-tasking operating system
Building Automation System N1 LAN • Communication between Network Control Units and Operator Workstations • Standard 2.5 Mbaud ARCNET LAN • Coax or fibre, bus or star • Object oriented protocol • Johnson Controls will release protocol information at no charge
Building Automation System OperatorWorkstation • IBM Compatible PC • Microsoft Windows Graphical User Interface • Scanned photographs • Autocad floorplans • Schematics built from symbol libraries • Real-time field data superimposed on background graphics
Building Automation System OperatorWorkstation • Historical data from NCU is archived in dBase files • NCU can archive data in multiple workstations concurrently so that data is not lost if PC fails • Other Windows programs can run concurrently • Other software can access BAS data using Dynamic Data Exchange (DDE)
Building Automation System NetworkTerminal • Hand held device for system access outside of control room • Can be connected to NCU or at remote connection • User friendly “finger mouse” operation • Access to all system data including historical data • Point names and password consistent with PC
Building Automation System Fire Panel Integration Chiller PanelIntegration
Building Automation System • Third Party Integration • A number of vendors have released their communication protocol to Johnson Controls. • Joint testing is done to ensure that the high level interface does not interfere with the proper operation of the third party system.
Building Automation System Software Features
Building Automation System • Limit unauthorized access • 5 levels of access • Monitor • Monitor, Control • Monitor, Control, Modify • Monitor, Control, Modify, Program • Monitor, Control, Modify, Program, Password • Same password used at PC and Network Terminal • Encrypted database stored at each PC and each NCU Password
Building Automation System Network Map Network Map JCTower - Vent + Electric + Air_Con - Level_05 - AHU_05 Level 5 Air Handling Unit VAV_05 Level 5 VAV Terminal Units Level_04 + Level_03 +
Graphic Window Graphic Window Graphic Window Building Automation System Graphic Penetration
Building Automation System • All information about a point in one summary • Line graph showing samples over past 24 hours for analog points • Dynamic line graph which updates every 20 seconds for analog points • Last 10 change-of-states (ON/OFF) with time/date for binary points Point Focus
Point Focus Window Building System Point History Current 10/10/94 07:00 16.7 10/10/94 12:07:15 12.3 30.0 30.0 10.0 10.0 Building Automation System Point Focus Window
Point Focus Window Building System Point History Current 10/10/94 07:00 16.7 10/10/94 12:07:15 12.3 30.0 30.0 10.0 10.0 Building Automation System Alarm Message CRITICAL ALARM EVENT 10/10/94 12:07:17 Building\System\Point 15.0 Deg C Hi AlarmTemperature is outside of normal operating range - ensure valve is under control Look Now Look Later Discard View System
Building Automation System Alarm Message Alarm message routedto multiple PCs Alarm eventdetected atNCU Alarm message routedto remote locationthrough modem
Building Automation System Report Router / Alarm Manager • Distribution system for messages and files • Manages alarm messages, Totalization files, Trend files and Point History files • Concurrent updating of multiple locations for fault tolerance • Feature executed by each Network Control Unit for fault tolerance
Building Automation System Archiving of Historical Files Copy of file archivedin multiple PCsin dBase format Historicalfile stored in NCU Copy of file sentto remote locationthrough modem
Building Automation System • Maintains records of run-time • Allows scheduling of preventive maintenance based on usage • Data archived in multiple PCs for fault tolerance • Built-in graphing functions • Data can be exported to other applications such as Maintenance Management software Totalization
Building Automation System • Periodic sampling of selected points • 12000 samples kept in each NCU • Samples archived in multiple operator workstations for fault tolerance • Built-in graphing functions • Data available to third party software Trend
Building Automation System • Continuous record of all points in the BAS System • Allows proactive response to occupant complaints or alarms • Data available at all Operator Workstations and Network Terminals • Unique feature only available with Metasys Point History
Trend Only Point History Building Automation System I will start collecting datanow and hope that the sameproblem happens again. I always have thedata required beforeI need it.
Building Automation System • Automatic execution of commands or summaries based on a time schedule • One time schedules to accommodate special situations • Automatic updating of point status after a power failure • Report generation by each NCU for fault tolerance • Default schedules in each DDC for fault tolerance Scheduling
Building Automation System Demand Limiting / Load Rolling • Advanced energy management algorithms • Actions co-ordinated between features • Prioritization of loads • Built-in safety parameters • Utility Profile to track electricity bills
Building Automation System • Remote PC can access network • Remote telephone can access network in tenant mode or operator mode • Critical alarms directed to: • Remote printer • Remote telephone (voice synthesis) • Numeric pager • Text pager Dial-Up I/O