Control and Automation Systems

1. Overview of Control and Automation System

 Building Automation
 Energy Management
 Building Management
 Control System Implementation
 Network Topology in BAS

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 Control and Automation Systems

Building Automation
 It is the integration of
 HVAC control system; lighting control system; fire/safety protection system; security
control system; and the access control system, through some sort of data communication
link.
 Electrical system, PA system, vertical transport system, car-parking system are
becoming part of it.
 It improves the operational efficiency.
 It allows distributed processing.
 It has multizones control capabilities.

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 Control and Automation Systems

 It enables sharing of information among various sub-systems

 in real time event
 of their databases
 of their historical file.
 It enables the building operator to manage the
integrated system from one station.
 In achieving the real integration, the owner/occupant can be
benefited. Examples
 electric load control scheme to reduce electricity usage
– selective reduction of lighting level
– selective elevator speed reduction; selective cars temporary parked
– temporarily reduction of HVAC load by incrementing set points
 fire management function
– real time access to monitor/control of building systems from fire
control panel
» receiving alarm/event
» override commands to smoke control system, elevator system,
electrically locked doors, auxiliary power and pumping systems.
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 Control and Automation Systems
“Intelligent” Building
 The integration of different systems together also bring along the
Integrated Building
 Up until now, the building industry cannot really enjoys all the
predicted benefits as promised by the “Intelligent Building Pyramid”
 Major blocking is due to two issues – Interoperability and Connectivity.

Computer Integrated Building /

Intelligent Building /
Integrated building Beyond 1995
Smart Building

Integrated systems Integrated Communication System 1990 - 1995

Building Automation System

Multifunction systems Security & Access Image 1985 -1990

HVAC & other plants control Text & Data Voice
control

Single function Electricity TV & image 1980 & Before

EDP & Data Telefax and
Security Access Control HVAC control Water, Lift Voice comm. comm.
Comm. Text comm.
control

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Intelligent Building Pyramid
Control and Automation Systems
Energy Management System
Energy Management
Building Automation System play a major role.
Energy management system (EMS) optimizes the operations, conditioning
processes, and indoor environmental parameters of building systems in order to
maintain a satisfactory indoor environment at minimum energy use (mainly in
HVAC and Lighting control).
On top of the requirement imposed by ASHRAE/IES Standard 90.1-1989 and
the DOE Standard (see appendix A), for buildings larger than 20,000 ft2 gross
area, HVAC EMS should include the following functions (the first four are also
required by ASHRAE/IES Standard):
 free cooling economizer cycle
 unoccupied period setback
 dead-band control
 supply air and space air temperature reset
 optimal preoccupancy warm-up and cool down
 duty cycling
 chiller optimization
 boiler optimization
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 ability to investigate worn or faulty equipment or component
 Control and Automation Systems
Energy Management System
 load limiting and shifting, kW demand
control
 submetering of gas and electricity end-use
for building tenants

 Example

e.g. use Energy efficient appliances

e.g. Encourage consumers to shift their electricity

consumption from peak periods to off-peak periods

e.g. Encourage consumers to reduce their

electricity consumption during peak periods 6
 Control and Automation Systems
Energy Management System
EMS are special purpose computerized
control system which can be programmed to
operate in an energy efficient and effective
manner.
 Lighting equipment
 HVAC equipment
– chillers, fans, boilers, pumps,
dampers, valves and motors, etc..
 Vertical Transportation equipment
(e.g. lifts, escalators)
Improve energy efficiency &
reduce energy demand
 Create environmental benefits
– reduce consumption of fuels and reduce emissions
from existing power plants and building boilers
– Improve IAQ (when more % of outside air is used) 7
 Control and Automation Systems
Energy Management System
Common methods for Energy Savings
Set-points
saving by reappraise and /or relax set-points
– e.g. set-point for cooling can be increased relative to an
increased external temperature.
– caution to match overall plant scheme in accordance to overall
control strategy.
– Regular review of set-points and modification is an essential
part of the ongoing energy cycle.
– Gradual change over a period of time to ensure smooth
transition
– 5-30% saving is possible.

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Control and Automation Systems
Energy Management System

Time Schedule
Only run the plant when the space is occupied
May need multiple switching periods of occupancy on
different days.

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 Control and Automation Systems
Energy Management System
Calendar Schedules
Use different switching patterns on different
calendar dates
Enable varied time scheduling to match varying
working working patterns
Good for exhibition halls or meeting rooms
Save operator time as can be configured once
Holiday schedule enable further
saving. (e.g. 8 public holiday,
5 working days/week, equate
to 3% saving)

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Control and Automation Systems
Energy Management System
Economizer
 For cooling system that has a capacity of 7.5 tons or more.
 Basic principle is to compare the external and internal temperatures, i.e.
based on how mild it is outside, and how high the internal temperature is
the cooling plant will be switched on at the least possible time, and
opposite for the optimum off function.
 A properly operating economizer can cut energy costs by as much as 10
percent of a building's total energy consumption, depending mostly on
local climate and internal cooling loads.
 Today, a choice of algorithms such as linear relationship between rate of
rise and internal temperature to enable a more accurate calculations of start
and stop time.
But, malfunctioning economizers waste much more energy than they were
intended to save.
 If it breaks down when its damper is in a fairly wide-open position, peak
loads shoot up as cooling or heating systems try to compensate for the excess
air entering the building, resulting from cooling excessive outside air. 11
 Control and Automation Systems
Economizer example

The components of an economizer: An economizer is simply a

collection of dampers, sensors, actuators, and logic devices that together decide
how much outside air to bring into a building. 12
 Control and Automation Systems
Energy Management System
Night Purge / Summer pre cooling
Where a cooling load at start of building occupancy is
required
External air is cooler than the required occupancy temperature
– This sequence enable central AHU plants to run in full fresh air mode
for a period of time (30 minutes is typical)
– Reduce the initial load on the primary plant at occpancy start
– Additional benefit of a fresh air feeling for the staff at occupancy
Load cycling
Switching off of electrical load for a period of time on a
regular basis
Applied to background plant such as a fan or pump where the
effect of it being turned off will not result in inconvenience
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Control and Automation Systems
Energy Management System

Load cycling(cont’)
Should allow override in the event of exceeding pre-set
such as high space temperature
Disadvantage: may cause an increase in electrical load
during start up; decrease the overall life of the plant.
Maximum demand
Applied to buildings where a limit is set for the maximum
consumption allowed(normally over a half-hour period)
A cost reduction measure by preventing this limit being
exceeded. When exceeded, a higher tariff per KW/H apply
Cost reduction is typically 3-5%
Some electrical loads will be shed and reinstated 14
 Control and Automation Systems
BMS - Example Architecture

 Invensys  System (Refer to diagram)

 Management Level
User can configure and monitor plant performance
Anticipate future trends, improve efficiency, analyse
management report
Automation Level
The location with greatest technical control requirement,
and differentiate one from others
 Controllers automatically perform their tasks from I/P and
to O/P.

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Control and Automation Systems
BMS - Example Architecture
Automation Level (Cont’)
Controllers can communicate with each other
– Peer-to-Peer
 Event based operation
– Function at the highest efficiency
– No repetitive information is transmitted
Controllers only react with the Management Level when
– Plant goes out of limits
– Adjustments are made through a user interface.

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Control and Automation Systems
BMS - Example Architecture
Field Level
Information is gather here
– Through sensors
– Through other intelligent devices
Information will be sent back to the controllers.
Third party equipment is integrated into the
Automation and Field levels with control at the
Management level

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Control and Automation Systems

Invensys  System
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 Control and Automation Systems

N1 NCU NCU NCU NCU

Remote/Dial-Up
Operator Workstation Operator
Workstation

VAV Controller
Lighting Controller

Fire Controller
Access Controller NEU Controller
UNT Controller
VAV Controller
N2

AHU Controller
⚫ Distributed Network
LCP Controller ⚫ Standard Components
N2
⚫ Dynamic Data Access
DX-9100 ⚫ Object Oriented Architecture

Johnson Controls’ Metasys

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Control and Automation Systems
Control System Implementation
selection of types of control systems
– simple local loop control
» Situation in which the subsystems are simple, and no multiple
units to be controlled; occupancy is relativity constant; no unusual
requirements, such as accuracy of control or abnormal ventilation.
– supervisory control of local loop control
» Situation in which diverse subsystems and environmental quality
and energy costs saving are important, and presumes that the
subsystems are not complex with a lot of interaction and are
adequately controlled by local loop controls.
– DDC (Direct digital control) integrated with BAS
» Situation in which there are subsystems need a lot of interaction,
such as multiple central chillers, variable occupancy schedule,
high standards of environmental quality, and the intention of
improving performance and energy costs. 20
Control and Automation Systems
Control System Implementation
Centrally controlled system
– A control system in which transmission is to a
central computer and the reliance of all controls
on a central computer.

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Control and Automation Systems
Control system implementation
Distributed control
A control system in which control computations and
intelligence are made at different locations and the
result coordinated.

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Control and Automation Systems
Network Topology in BAS
Bus topology- All devices are connected to a
central cable, called the bus or backbone.
Ring topology- All devices are connected to one
another in the shape of a closed loop, so that
each device is connected directly to two other
devices, one on either side of it.
Star topology- All devices are connected to a
central hub. Star networks are relatively easy
to install and manage, but bottlenecks can
occur because all data must pass through the
hub.
Hybrid Topology - Network topology which
combines more than one basic topology such as
bus, ring, or star.

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Control and Automation Systems
Example
Backbone Star Topology Wiring in Building

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Control and Automation Systems
Example
Backbone Bus Topology Wiring in Building

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Control and Automation Systems
Example
Backbone Ring Topology Wiring in Building

Adv

disedu

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 Control and Automation Systems
Consideration in Topology Layout
 Automating buildings with vast amount of points require a well-designed network
segmentation, in order to achieve a good performance & infrastructure.
Well designed structured network by using repeaters, bridges or even better
using routers to improve network reliability and simplify network
troubleshooting
Some reasons why segmenting a network is important:
 Isolation of individual network segments in order to limit the propagation of a
single fault to one segment and prevent this single fault from spreading out over
the entire network
 Different nodes demand different communication media and different network
speeds but they all need to communicate with each other, which requires an
interconnection between the different networking media.
 Increase the number of possible nodes in a single network (e.g. max. 64 nodes
per FT-10 segment)
 Increase the physical dimension of a network (e.g. 500 m for an FT-10 segment)
 Keep local traffic within one segment in order to avoid network traffic overload
conditions, which will make services like HVAC, lighting, … malfunction. 27
Control and Automation Systems
Example Structured Layout

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Control and Automation Systems
Example System Design

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 Control and Automation Systems

Appendix A: ASHRAE/IES Standard 90.1-1989

 Gas and electricity individually metered, monitored, and
recorded except for those buildings less than 5000 ft2 gross
area.
 For HVAC&R eqipment with energy input exceeding 20
kVA or 60,000 Btu/h, a facility to measure their input and
output performance individually.
 Means to read, to record, and to summarize their energy
consumption.
 Optimum starting and stopping of the HVAC&R systems,
and indication of their operating time schedule.
 Monitoring and resetting of HVAC&R control system to
ensure proper operation.
 Off-hour readily accessible means and energy efficient
operation schedule.
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