An overview of central control and monitoring systems for large buildings and building complexes

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An overview of central control and monitoring systems for large

buildings and building complexes

AN OVEIIW 1E# 01:

CENTRAI. GONTIEOL AN[) MON I 'I'I)II I id(; S'iStl'l 31S

1;OIl

LARGE BUILDINGS

.AND

BUI LL)INI; COFIFLEXES

A.H. Elmahdy

INTRODUCTION

C e n t r a l control and monitoring systems (CCMS) can b c of various levels o f sophistication depending an t h e s i z e of t h e building and

the desired operational function. The simplest system i s one that

allows an o p e r a t o r to check t h e operational s t a t u s o f h e a t i n g , v e n t i - l a t i o n and air conditioning ( W A C ) , fire and security systems, a n d to

control v a r i o u s equipment remotely from a central console. The most

complex system h a s a d i g i t a l computer t h a t performs ilrost of tIlc work

t h a t t h e o p e r a t o r rlori~ui 1 l y docs i n ;~clcli tian t o o t h c r opt irr~i = a t ion i111d managcmcnt f u n c t i o n s . 'I'his type o f s y s t c ~ i i is k11ow11 ;IS "d i rcct J i x i t a 1 controlM (1)IlC)

.

The main o b j e c t i v e of t h i s s t u d y is _{to provide guidance t o b u i l d -}

i n g owners and personnel in t h e selection of a c e n t r a l c o n t r o l and

monitoring system suitable for a s p e c i f i c building o r group o f build-

i n g s . I t is a l s o aimed at estimating t h e annual energy savings re- s u l t i n g from u t i l i z a t i o n o f CCMS and o f estimating t h e payback period

f o r various types of systems. A survey was made, t h e r e f o r e , to g a t h e r

information regarding the i n i t i a l and o p e r a t i n g cost of CCMS, over-all

s a v i n g s and the f r a c t i o n s of t h e s e s a v i n g s c r e d i t e d to each individual

energy conservation measure. F o r most o f the systems surveyed, it was

possible to g a t h e r d a t a about t h e capital c o s t , t h e number of ~onitored

p o i n r s and the various design and o p e r a t i n g Eeaturez. But it was im-

possible to i d e n t i f y t h e annual savings c r e d i t e d only t o t h e use of

CCM$

.

As a normal p r o c e d u r e , p r i o r to installing a CCMS, a retrofit

program i s c a r r i e d o u t to bring t h e building and i t s various services i n t o normal acceptable performance. T h i s program usually continues

a f t e r the CCMS has been installed. Thus, it becomes a l m o s t impossible

to e v a l u a t e t h e energy s a v i n g s credited to t h e use o f CCMS a l o n e .

Nevertheless, in most cases, the r e t r o f i t programs would nor have been carried out without t h e idea of insralling a c e n t r a l c o n t r o l system.

In t h i s r e p o r t t h e results o f t h e f o r e g o i n g survey are presented showing the main d e s i g n features and areas of application of some

sysrerns. Total c o s t o f the system and the number of points m o n i t o r e d

are used to develop a simple g u i d e l i n e for selecting a suitable CCMS for a g i v e n l a r g e building o r group of buildings.

BUILDING

AUTOMATION AND ENERGY CONSERVATION

Automation centres used to control and operate

HVAC

systems utilize software packages to perform some p~eselected functions.

These packages consist

of

one o r more of the following energy con-

servation programs.

1. Sta~t/Stop Program. T h i s represents t h e simplest, y e t t h e most

e f f e c t i v e , energy s a v i n g program. It is designed to s t a r t and

stop

different W A C equipment automatically according to a pre-

determined schedule. For example, i n a feasibility s t u d y made

to investigate t h e possibility of installing a central control

and ~ t o n i t o r i n g system

in

Dalhousie U n i v e r s i t y , it was estimated

that programmed start/stop

functions

of h e a t i n g , coolialg,

humidifying and electrical systems would r e s u l t in a b o u t 85 p c ~

cent of the t o t a l n e t savings (1)

-

The a d d i t i o l ~ a l 15 per ccnt

saving is obtained by implementing some other E u ~ z c t i a n such iis

nixing damper adjustment o r supply air temperature reset.

2. Reset Program. T h i s program calculates actual cooling loads i n

various zones and resets t h e s u p p l y a i r temperature so t h a t mini-

mum cooling and r e h e a t i n g w i l l occur. This a c t i o n saves energy

by matching t h e system to t h e actual building l o a d d u r i n g off-

d e s i g n conditions.

3 . S t a r t Time Optimization Program. The purpose o f this program is

to ensure t h a t in buildings t h a t shut down t h e

air

conditioning

equipment d u r i n g t h e silent hours, comfort conditions are restored

i n t h e l i v i n g space in time for occupancy. Eventually, t h i s would

minimize the o p e r a t i n g time of major energy consuming equipment

s u c h as chillers, boilers, and individual a i r handling units.

4 . E l e c t r i c llcrnand Corttrol lJrogram 'l'hc b a s i c o b j e c t i v e of this

program is t o vary some c o n t r o l l a h l c o r discretionary p o r t i o n s of

t h e buildins electric load t o compensate f o r load requirements

elsewhere i n o r d e r t o p r e s e n t a more n e a r l y c o n s t a n t total building

demand to t h e u t i l i t y company. T h i s is accomplished by t u r n i n g off

some e l e c t r i c loads f o r s h o r t l p e r i o d s of t i m e t o shave o f f t h e ex- c e s s i v e l y h i g h peaks i n the electric load p r o f i l e and put t h a t energy t o use i n t h e "empty valleys" o r just save t h a t e n e r g y 123,

(Figure I ) .

Sometimes this program is called "duty c y c l e y \ When it is used t h e space temperatures are permitted to drift slightly w i t h -

out u p s e t t i n g space comfort. T h i s would r e s u l t in energy saving hecause o f t h e increased equipment shut-off time. The d u r a t i o n

and frequency of load c y c l i n g can b e assigned individually to each

load with a rolling priority list, whereby a specific p i e c e of equipment is shut down for a s p e c i f i c period of time. This rolling

p r i o r i t y i s ser by t h e building operator or manager and c o u l d be

5 . 11i~ch:ilpy Cant r o l l ' r o g r : ~ ~ ~ ~ . il lso known ;IS t h o outrloor a i r qrlant it)?

o p t i m i z n t ion prsgriim. When ;I sp;lcc rcrlui rcs c o o l i n g , tllc c n t h : l l l ~ y

( t o t a l Ilc:lt c o n t e n t ) of t l ~ c otttrloor ancl r c t u r r i : l i

r

a r c mot~itorctl

.

,

and compared. Ihus, who11 t h e cnt11;llpy o f o u t d o o r a i r i s 1owt.r t h a n t113t of t h e r c t u r n a i r , a l a r g e r p e r c e n t a g e o f outdoor ; l i r is

mixed w i t h a smaller p o r t i o n o f r e t u r n air. T h i s i n t u r n reduces

the chillers l o a d , and

is,

therefore, c a l l e d "free c o o l i n g . "

6. C h i l l e r Load Optimization Program. This program i s used when a

group of buildings is supplied with cold water for the cooling system by

a

multiple c h i l l e r p l a n t . The program is designed to

maximize t h e c o o l i n g p l a n t efficiency d u r i n g all o p e r a t i n g condi- t i o n s and ensure minimum energy consumption. The over-all c o o l i n g

p l a n t efficiency v a r i e s w i t h t h e imposed cooling load, condenser

water temperature, and chilled w a t e r t e m p e r a t u r e . I n t e r a c t i v e c a l c u l a t i o n s are u s u a l l y used to reach f o r t h e most e f f i c i e n t o p e r a t i n g c o n d i t i o n s by t a k i n g i n t o account cooling p l a n t l a y o u t ,

the number o f series and parallel chillers and whether or not n

heat recovery system is used.

7. B u i l d i n g Management: - Programs. Large building automation c e n t r e s have been u s e d to a s s i s t those directly r e s p o n s i b l e f o r buildings

management. The totalization capability of some complicated

systems h a s been extended to p r o v i d e u t i l i t y l o g s and u t i l i t ; , . rend r e p o r t s . S t a n d a r d p r o g r a m s are u s e d t o provide integrated daily

o r monthly cooling and h e a t i n g loads, d a i l y o r monthly, kwh, k W

demand and total gas, oil and electricity consumption.

8, Preventive Maintenance Program. Totalization of machine running

t i m e has enabled maintenance personnel to service different equip-

ment p r o p e r l y based on t h e total accumulated running time. T h i s

program a l s o provides p a r t s replacement work orders, maintenznce

summary reports and information about equigmenc breakdown.

9 . Light Control Program. This program is used to c o n t r o l lights in various zones o f a hKilding or group o f b u i l d i n g s . .% d i r e c t and

profitable advantage of a light control system is t h e ability t o reduce e l e c t r i c peak demand q u i c k l y when it reacl~e.: the critical

range.

LO. F i r e A l a r m s and Life S a f e t y . i n addition t o energ;: conservation and

management programs, a d a t a based computerized system for l i f e s a f e t y ,

f i r c alarms, and smoke control operations can be designed to work i n

parallel. w i t h IIVAC systems.Visua1 display may be i n c o r p o r a t e d

ro

in-

d i c a t c fire locations and safe emergency e x i t s . Smoke control

r o u t i n e s i n c l u d e c o n t r o l o f s p e c i a l fans and a i r handling u n i t s , as

well as dampers to s e t up the safcsb a i r f l o w a n d static pressures

in the troubled [and surrounding) areas.

11. Power Demands Forecast Program. To m a i n t a i n an economical p l a t e a u

of electrical e n e r g y consumption, t h e power demand Eorecast p r o g r a m

exceed a p r e s e l e c t e d usage l i n t i t , thc c e n t r a l f n c i l i t y is nlcrtcJ and t h e electric demand control program i s executed. Once the p r o j e c t e d usage t r e n d s are within t h e allowable g u i d e l i n e s , t h e

central facility returns the

HVAC

system t o t h e normal running

mods.

The foregoing programs cover most of the functions used to save

energy in buildings, when utilizing c e n t r a l control and monitoring

systems. As e x p l a i n e d earlier, t h e s e programs function as an inte-

grated system and interact w i t h each other on a continuous basis. Con-

sequently, the n e t energy saving is t h e sum o f t h e contribution o f each of t h e s c programs. T h i s makes it v e r y d i f f i c u l t to isolate the s a v i n g s c r e d i t e d t o each individual program. Nevertheless, more sophisticated

simulation and energy analysis programs could b e used to estimate t h e a v e r a g e energy s a v i n g of each of t h e s e programs.

CCMS

CLASSIFICATIONS

Several t y p e s of CCMS are now available co~mnercially. Most ef t h e major control firms and o t h e r companies in t h i s f i e l d have introduced

families o f building automation systems t h a t are i n t e n d e d t o be used

f o r a wide range of b u i l d i n g sizes. These systems may b e classified i n t o

four categories.

Class A Systems

These consist of small monitoring and control systems that could

b e used in buildings with f l o o r areas up to about 20,000 m2. The basic

component of t h e s e systems is a micro-processor preprogrammed to s t a r t /

s t o p d i f f e r e n t HVAC s y s t e m components according to a preselected schedule.

The systems can be designed to perform o t h e r operations s u c h a s monitoring

f i r e alarms, smoke detectors, security checks and load cycling. Examples

of some systems that would f a l l i n t o this class are:

-

Johnsonis Control JC80-35, Figure 2

-

Powers

-

Conspec Sentusion 200, F i g u r e 3

-

Honeywell Delta 2000, F i g u r e 4

-

Powers 5-170 Energy

-

Enerteck 80,

-

Automatic Logic System.

Class B S y s t c m s

These systems arc similar t o t h o s e i n Class A except that t h e y a r e

capable of handling larger buildings and some b u i l d i n g complexes. The

central facility includes cathode-ray tube (CRT) terminals, s l i d e

p r o j e c t o r s and intercom communication l i n e s . The saftware packages in

most of these systems a r e programmed to perform functions such a s :

-

Executive and o p e r a t i n g i n s t r u c t i o n s - Scheduled s t a r t J s t o p operation

-

Load rotation and s h e d d i n g

- Optimization of start time - Enthalpy optimization program

- F i r e alarms and l i f e safety s y s t e m m o n i t o r i n g

These systems are usually capable of handling about 2000 addrcs-

s a b l e p o i n t s , and t h e memory of t h e c e n t r a l processor is l a r g e enough to handle data for more t h a n one building. \+%en these systems are used

f o r a group of buildings or b u i l d i n g complexes, t h e c e n t r a l control

f a c i l i t y i s connected to remote data g a t h e r i n g panels by means o f one o r

more types o f data communicatian links. Examples of systems that would

f a l l

in

this class are:

- Johnsonts Control J C 80-55

-

Powers S-570

- Honeywell Delta 1000

When more t h a n one d a t a gathering panel i s s e r v e d by a c e n t r a l f a c i l i t y , each p a n e l i s a l l o t t e d an equal amount of time d u r i n g which

it i s i n d i r e c t communication w i t h t h e central facility.

As t h e number of data g a t h e r i n g p a n e l s increases e i t h e r t h e time a l l o t t e d each panel becomes shorter or communication between the i n d i v i -

dual p a n e l s and t h e central facility hecomes l e s s frequent. To overcome

this inefficient communication, the data gathering panels a r e d i v i d e d i n t o groups. Each grorlp is w p e r v i s c d and scrvcd hy n s e p a r a t e remote ~ ~ r o c c s s i n g u n i t (11I3U)

.

Each R1'11 stores t h e softwrrrc n l g o r i t h u s rcqu i r c d t o o p c r a t r t l ~ c C O I I I I O C ~ C ~ cant r o l 110 i nt s , w h i 1c ;IT t l l c s;1111~ t ililc IFCI 11g

e o t ~ l ~ e c t c d to t l ~ c ccntr:rl facility i n orclcr to t r r ~ n s f c r t l ~ c ovcr-;11 1

control s t r n t c g i c s and any chnngcs i s s ~ t c d by tht. ollcrntor. 11s n rcszllt, a l l remote ~ ~ r o c c s s i n g u n i t s a r c connected t o the central f a c i l i t y i n n ilierarchical t y p e of network, [Figurc 5). An example o f t h i s arsangcntcrlt

is the J o h n s o n J C 80/55 system ( 3 ) i n operation a t t h c U n i v e r s i t y of

Western O n t a r i o . Description of s h e features of this system is outlined

in Appendiv I .

Class

C

Systems

T h i s group represents the h i g h e s t degree o f sophistication in

c e n t r a l c o n t r o l and m o n i t o r i n g syszems; t h e y a r e usually r e f e r r e d t o as " d i r e c t d i g i t a l c o n t r o l CDDC)" systcms.

A t y p i c a l DDC c o n f i g u r a t i o n is i l l u s t r a t e d by the heating cokl

control loop b l o c k diagram shown in Figure 6 . The s e n s i n g elements

and transducers a r e u s u a l l y located a d j a c e n t to t h e W A C equipment. The

sensor produces an analog s i g n a l p r o p o r t i o n a l to the physical parameter of interest, e . g . , duct air temperature. T h i s s i g n a l i s transmitted t o t h e c e n t r a l computer, where the control action is determined. An analog o u t p u t s i g n a l is issued by the computer reflecting t h e preprogrammed control strategy.

A comparison between a common pneumatic c o n t r o l and DDC arrange- m e n t s i s b e s t i l l u s t r a t e d diagramatically i n F i g u r e s 7 and 8 . F i g u r c

I n this case, each component of t h e HVAC system i s i n d i v i d u a l l y corltrolled and scheduled

v i a

a receFver/controller. T h u s , each control element a c t s

independently o f the others, without t a k i n g into account t h e over-all system performance; t h i s would normally result i n wasteful, s i m u l t a n e o u s h e a t i n g and cooling. \%%en the DDC concept

is

applied on t h e

same

HVAC system, t h i s i n h e r e n t i n e f f i c i e n c y i n o p e r a t i o n i s c o n s i d e r a b l y reduced.

Xn Figure 8 , the sane air handling unit illustrated in Figure 7

is

shown w i t h some m o d i f i c a t i o n s f o r t h e

DDC

link to the central control facility.

The pneumatic regulators are eliminated and actuators are linked to a

remote micro-processor unit CRMU), which in t u r n

is

connected to t h e

central processing unit [CPPT). The DlU schedules each component in t h e IWAC unit as p a r t of an integrated system.

'I'hi s type af system i s uscrl For twi l d i n g coliqllcxc-s sucl~ 11s cJarlr;l-

t i o n a l institutes and university callqmses. I n addition to t l ~ c t ~ s i c

f u n c t i o n s d e s c r i b e d earlier, t h e advantage of h a v i n g a largc d a t a s t o r ; ~ g t '

and on-line computer makes it p o s s i b l e t o i n c l u d e t h e following functions:

- Reset of supply air system program

-

Optimization of cooling and h e a t i n g p l a n t s operation

- Building management program

- L i g h t s control program

- Preventive maintenance program

- Energy auditing and e f f i c i e n t bookkeeping

Appendix I I g i v e s a d e s c r i p t i o n of a d i r e c t digital control system

in operation at the University of Saskatchewan campus, together with a

summary of t h e d i f f e r e n t operational functions performed by

the

CCMS.

C l a s s D Systems

I n s t a l l a t i o n of a central c o n t r o l and m a n i t o r i r ~ g systci~i is n e i t h e r economical nor p r a c t i c a l f o r small b u i l d i n g s because u f t h e rclativcly

h i ~ h i n i t i a l and o p e s a t i n g c o s t s . The altcrnativc i s to n o ~ ~ i t o r a n d

control buildings i n a wide geographical area from a s i n g l e location.

The b e n e f i t s of a building automation c e n t r e can be obtained by

purchasing t h e service r a t h e r t h a n providing it independently. I n this

case, t h e manufacturers install the CCMS in a centralized location of t h e area to h e served. The purchased building automation service may

i n c l u d e most of serviccs t h a t could b e obtained by owning a central

m o n i t o r i n g and c o n t r o l system, but wixhout t h e burden of maintaining

thc system i t s e l f .

Examples :

1 - TABS - Total Automated B u i l d i n g S e r v i c e :

Johnson's Controls CQ. will provide building monitoring and control

s e r v i c e s on a rental b a s i s . T h i s service includes installing t h e data g a t h e r i n g p a n e l s on t h e site and connecting t h e communication l i n k s between t h e central f a c i l i t y and t h e customer's building.

2 - BOSS - Building Operating System S e r v i c e s :

T h i s scrvice i s available from Honeywell Co. on a rental b a s i s .

It i s similar to TABS p r o j e c t

i n

many aspects. It utilizes t h e

Honeywell Delta 1 0 0 0 system which i s connected t o individual

buildings by means o f dedicated telephone lines.

3 - ADMIC - Central Control and M o n i t o r i n g System:

Adaptive Microelectronics Ltd. [ADMIC) provides c e n t r a l control and

monitoring services for buildings from a central facility by means

of dial-up telephone system.

SELECTION OF CCMS

For a particular b u i l d i n g o r building complcx, the p r c l i m i n n r y

stlrvcy o f tllc e x i s t i n g IIVAC systcm nncl dcsircd control f ~ n n c t i o n s 511ed some l i g h t o~r sllc t o t a l nunt~cr o f ~ l o i n t s t o he n l n t l i torccl. 'I'llc outcn111~ of this survey is irscd i n c s t i t e a t i n g tIic i n i t i a l c o s t a s 1 ~ 1 1 a s t l ~ c

suitable hind of CL'MS. Table 1 i s a summary of soinc CCllS 41tsta11ccl i n

buildings of v a r i o u s sizes, showing t h e t o t a l c o s t , the number of

monitored p o i n t s and t h e cast per p o i n t f o r each system. It is e v i d c ~ l t

t h a t t h e c o s t per point decreases as t h e number of p o i n t s increases and

approaches an almost constant value. Figure 9 illustrates this t r e n d

for t h e number of CCMS included in this study. It should be n o t e d t h a t , due to sapid change in prices of e l e c t r o n i c equipment, t h e dollar values presented i n this study i n d i c a t e only a relative p r i c e scale and n o t t h e

present market p r i c e s .

The t o t a l number of monitored p o i n t s is an important f a c t o r in

s e l e c t i n g a CCblS. Each system h a s a certain number o f p a i n t s t h a t it

can handle e f f i c i e n t l y , and any additional p a i n t s t e n d t o overload the

system. T h i s r e s u l t s i n an i n e f f i c i e n t operation and sloigcr speed of

communication bctwccn the ficld d e v i c e s and the c e n t r a l f a c i l i t y .

I n d c t c r n i i n i n g t h c t o t a l number of p o i n t s 3 s y s t c r n c;in h:i~~rlLc e f -

f i c i e n t l y futurc expansion of the building a s w e l l as the ]>ossil~ilit!-

of implementing some other program or e n e r g y conservation measures,

s h o u l d be investigated. Such expansion o r new measures u s u a l l y result i n an a d d i t i o n a l number of aLLouable p o i n t s and l a r g e r computer memory to store t h e a l g o r i t h m s and the p e r t i n e n t information.

F o r example, t h c economizer cycle program minimizes t h e e x p e n d i t u r e of cooling cnergy by u s i n g proper amounts o f outdoor a n d / o r r e t u r n a i r .

'Yhc f o l l o w i n g points have to be monitored t o u t i l i z e t h i s p r o g r a m f o r

each a i r handling u n i t (Figure lU],

- outdoor air d r y bulb temperature - outdoor air dew point temperature - return air dry bulb temperature

- r e t u r n a i r dew p o i n t temperature - selected leaving air temperature

Some of these p o i n t s may already have been monirored f o r seine

other purpose; t h e remaining points are t o b e connected t o t h e c e n t r a l

facility via t h e d a t a gathering panels. Othcr energy conservation

measures nhicil may r e q u i r e additional paints are:

- load cycling program

- chillers optimization program

-

scheduled supply a i r temperature reset

- light: control program

- preventive mainzenance program, e t c , The procedure t o s e l e c t a s u i t a b l e CCMS can be summarized as

follows:

1. Study t h e e x i s t i n g W A C system to determine t h e approximate number

o f points to be monitored;

2. Determine the control and other functions required including the

energy conservation measures, management, s e c u r i t y , etc;

3 . Make provision f o r future e - q a n s i e n in buildings, control s t r a t e g i e s and o p e r a t i o n a l f u n c t i o n s ; and

4 . Estimate the payback time o r rate of return on t h e money invested

t a k i n g into account anticipated increases i n c o s t s o f labour and e n e r g y .

Eigurc 9 may b e used t o estimate t h e i n i t i a l c o s t of t h e CCMS based on t h e estimated t o t a l number of p o i n t s . It also g i v e s some guidance on

which system i s suitable f o r that p a r t i c u l a r p r o j e c t .

F o r example, if the number of points is below 100, then leased

building services (Class D systems) a r e more economical t h a n a privately

owned system. In case leased building services a r e not available i n t h e

area, automatic time clocks (or similar electronic devices) can be used

to achieve equipment scheduling.

I f t h e number of points i s between 100 and 200, then Class A Systems

might b e used at a reasonable c o s t . This would p r o b a b l y b e the case

with medium and l a r g e o f f i c e buildings of between 10,000 and 20,900 m 2 .

For a group o f buildings where the number sf rnonttored points is between

500 and 1500, Class 5 Systems are believed to be _{s u i t a b l e and more econo-} mical. This would p r o b a b l y be the case for building complexes such as university campuses, educational institutes, and p e n i t e n t i a r i e s .

I n t h e case of a large building complex (20 buildings or mare) t h e

number o f monitored p o i n t s usually exceeds 2r100. I n t h e s e

situations, the direct digital c o n t r o l systems (Class C Systems) may h e

appropriate, The c o s t per p o i n t f o r t h e DDC systems is u s u a l l y highcr

t h a n t h a t o f t h e other classes, but t h e additional benefits a r e o f t e n s u f f i c i e n t t o j u s t i f y t h e extra cost. Although t h e c a p i t a l c o s t of this

class of system is relatively high, it has many a d v a n t a g e s over the other classes, i , e . ,

1, DDC s y s t e m is expandable i n terms o f number of p o i n t s a b l e t o be

monitored, software packages, and o p e r a t i o n a l f u n c t i o n s .

2 . It i s more reliable t h a n pneumatic c o n t r o l systems.

3 . Failure o f t h e c e n t r a l facility d o e s not u p s e t t h e individual

control u n i t s because s a t e l l i t e processing units are p r o g r a m e d to

stand a l o n e in such cases.

4. L a r g e r computer memory allows t h e building management t o u t i l i z e a preventive maintenance program and perform energy a u d i t s for the

d i f f e r e n t buildings.

5. Electronic components a r e usually a v a i l a b l e from several computer

m a n u f a c t u r e r s . T h i s has the advantage o f n o t being r e s t r i c t e d t o

a p a r t i c u l a r company f o r equipment maintenance, and, in most cases,

r e s u l t s i n

a

r e d u c t i o n i n t h e operation c o s t of the CCbIS.

6 . Although t h e i n i t i a l c o s t of t h e DDC systcms i s reIatively h i g h c r ,

t h e payback period is comparable w i t h those of smaller systems.

T h i s i s expected because more energy saving measures a r e implemented

when using DDC systems as explained earlier. Table I1 g i v e s a sum-

mary o f t h e payback p e r i o d o f some CCEIS.

COMMENTS AiiD CONCLUSIONS

1. B u i l d i n g a u t o m a t i o n systems c o n t r i b u t e t o conserving, e n e r g y because o f better control of energy consuming equipment.

2 . CCMS have t h e advantage o f r e p o r t i n g off-normal conditions before

t h e y are registered as a complaint resulting from uncomfortable

conditions i n t h e occupied space.

3, T r o u b l e areas are e a s i l y identified; CCMS provide.: t h e mairltenancc p e r s o n n e l and e n j o y s t h e convenience of c h e c k i n g 011 the HVAC system components w i t h o u t p h y s i c a l l y having t o visit the systein in various

buildings.

4 . Major c o n t r o l companies s u p p l y , install and maintain t h e CCLIS e q u i p -

ment. T h i s has t h e disadvantage of heing totally dependent on t h e

supplicr f o r any changes, modification, or updating o f t h e existing

system.

5. l i x t e n s i v c e n g i n e e r i n g studies a r e always necessary to s t u d y t h e

e x i s t i n g llVAC systcms, operational functions desired from t h e CCMS

311d tllc p r o j e c t e d expansion in b o t h lluildings and moni t a r i n g s y s t e m .

These arc usually done p r i o r t o c o m m i t t i n g a l a r g e sum of money t o a

s p c c i f i c l ~ u i l d i n g automation system. Unfortunately, t h e r e have been somc cnscs where t h e management personnel had to replace t h e installed

CCMS i n s r d c r to avoid i n e f f i c i e n t o p e r a t i o n of t h e existing system.

O . Managcmcnt p e r s o n n e l are often c o n c e r n e d about equipment obsalescence,

p a r t j . c u l : i r l y i n t h e clectranics field. This concern i s j u s t i f i e d

by t h e r n t h e r significant changes i n electronic equipment f o r building

building automation systems minimizes t h e negation of o u t d a t e d systems.

7.

In

mest cases, building automation systems do not r e s u l t i n reduced

manpower, but a central control system can assist

i n

making b u i l d -

i n g management and maintenance personnel

more

e f f i c i e n t , particularly

when implementing e f f e c t i v e preventive maintenance programs.

8. Problems i n e x i s t i n g W A C systems and controls should be corrected

before the installation of a control c e n t e r . Otherwise these problems

will be c a r r i e d o v e r t o t h e new center and be compounded.

9 . Finally, there has been great difficulty in o b t a i n i n g informati011

about e x i s t i n g CCMS. For exnmplc, management and system l ~ e r s o n n c l

are usually rc luctitrit t o r c l c n s c acczil';itr. informntion :~I)out s y s tcni

c o s t , o p e r a t i n g c o s t , frequency of CCMS failure, and tE~c d i s a d v a n -

tages and inefficiency

in

operatioa 05 the system.

REFERENCES

I . Chorley and Bisset Ltd. Feasibility Study f o r C e n t r a l C o n t r o l

System, Dalhousie University, Halifax, N-S., October 4 , 1976.

2 . Molnar, J. Electrical Demand Cost Control Factors. Building

O p e r a t i n g Management, August 1978, p . 5 4 .

3 . Johnson Controls I n c . The Big Idea i n B u i l d i n g Automation. Milwaukee

,

Wisconsin.

4 . Petievich, G.M. Facilities Management System. Massachusetts

TABLE I

OVER-ALL COST, NUCIBER OF POINTS AND

COST PER POlNT 01: SOME CONS

'I'O'l'AL

COST

NO. 01:

PO

l NTS PROJECT SYSTEM Gue lph University Johnson T 6500 York University Honeywell System 6 Selectographic Univ. o f Lethbridge Honeywell Delta 2000 McMa s t e r

University DEC Eqp.

LIospital f o r S i c k Children Johnson T GOO0 Toronto Dominion Bank Johnson T 6000 NRC D e l t a 2000 M.I.T. Campus Boston Univ. of Western Ont a r i a Univ. of Saskatchewan Place de V i l l e O t t a w a Univ. o f Alberta DDC E)alhousic. Uniu. (Proposed) I,;.~kcheaJ U n i v . [Proposed)

PORT I I 1

I

DATA CONCENTRATOR

I

EVENT OMMUNlCATl ON :S TO FIELD DEVICES J R E 3 O C K D I A G R A M S H O W I N G THE S E N T U R I O N 2 0 0 S Y S T E M PROAf CT OR

ADDRESS AND DATA DISPLAY

VISUAL DISPLk'f I-,5NT?OL

START-STOP PFCSPM~

Dl GlTAL SCAN h l"4G

REAL-TIME CON'P'JL

PROJECTOR dOF.T?OL TELETYPE C G N T i S L TREND 'LOG CONTZOL

PILOT LIGHT C G h T f D L

F I G U R E 4

D A T A P R O C E S S I N G C O M P U T E R F A C I L I T Y REMOTE P R O C E S S O R U N I T S F I E L D P R O C E S S O R S P R O C E S S I N T E R F A C E

NOTE: Dashed l i n e s i n d i c a t e f u t w r e expansion

F I G U R E 5 H I E R A R C H I I C A C N E T W O R K P R O C E S S OUTDOOR A I R T E M P E R A T U R E SENSOR A N D T R A M S M I T T E R AIR F L O W I E L E C T R I C TO P N E U M A T I C r T R A N S D U C E R I T E M P E R A J W R E I I I H O T W A T E R SUPPLY L , r _e

j

I

1 H O T W A T E R R E T U R N 1

!

1

I M A N U A L D I R E C T D I G I T A L O P E R A T O R f N P U T

I

'---+

I TO C E N T R A L C O M P U T E R L M O N I T O R I N G S T A T 1 O N t I G I I R C o I Y P I S A L D I R E C T W l G l T A L C O N T R O L LOOP

'"

C3

CCMS 1 400 NUMBER OF P O I N T S I FIGURE 9 C O R R E L A T I O N B E T W E E N T H E NUMBER OF P O I N T S A N D T H E I N I T I A L C 0 5 T / P 0 1 N T O F C C M S 3 P 5 9 6 6 - T

1

I

I

t

1

1

I

DEl?' RETLIRN POINT _AIR DATA W L6 GATHER1 NG PANEL POINT 1

I

-

- I WATCH DOG DELAY C!RCUIT I I L - 3 - 15 PSI E 200 I 1 0 0 0 800 6 0 0 - < L A 5 5 i, U D l I

*

C L A S S D

'\

\ \ \ \ \ 1 \ '0 O X \ 1

.

\

-

.

\

.

\

-- .

-

- -

I \ -1 \ 0 _<

--

0

--

--

\ _1.

-

.

--

--

0 Q

'

.

,

0 '

---

I

400 -

.

0 '*. \ 0

'.

-

-

.

' O .

--

- --

-_

\ 0

-I

i

' s 0 200

---

A 0 I

I

I

1 0 5 0 0 1 ooo 1 500 2 000 2 500 3 000 T 5110

I

d aoo

APPENDIX A

CENTRAL CON'FROL

AN!)

blllN ITBK 1 NG SYS'I'EICE

7'lIli UNlirI!l<S I'lT Lll' I ~ I ~ S ' I ' I ~ I ~ N O N ' ~ A l < 1 0 L~~\i*ll'lJS

'I'l~c university cnmpus consists of 3 8 rnajor b u i l d i n g s , 2b of which are connected t o the c e n t ~ a l c o n t r o l and monitoring systerl.

The total f l o o r area served by the CCMS i s a b o u t 3 2 5 , 0 0 0 m2. A c e n t r a l control system was installed on t h e university campus to

w h i c h 1200 p o i n t s are connected to monitor and c o n t r o l about 200 air

handling systems. The CCMS is a JC/80-55 which c o n s i s t s of t h e

f 01 loving main components :

1 - A Cathode Ray Terminal [CRT) that serves as the primary device

used t o d i s p l a y i n f o r m a t i o n and t h r o u g h which data are e n t e r e d

2 - A s l i d e projector t h a t displays schematic diagrams o f each system

connected to t h e CCMS

3 - A teletype p r i n t e r t h a t records alarm conditions and o t h e r o p e r a t i n g

activities which a r e used t o facilitate analysis of conditions

4 - R hi-speed p r i n t e r o f d a t a l o g g i n g and system s t a t u s reports

5 - A c e n t r a l computer c o n t a i n i n g a 32K processor, a 524K f i x e d hcad

disc s t o r a g e and n p3per t a p e record~r

I:igurc A-1 i s a hlock cIi:!~ratt~ ~ I I o w ~ I ~ ~ t l l ~ o r g : ~ t l i ~ : ~ C i o t l o f tllc

c c n t r n l control systems.

SYSTEM FUNCTIONS

1. Operator Commands

- s t a t u s display o r p r i n t o u t of any s i n g l e p o i n t , s y s t e m ,

building, o r summary of a l l p o i n t s

-

stop/start, o n / o f f , open/close, high/low speed o p e r a t i o n s - adjustment of t h e s e t t i n g s o f temperature and humidity

controllers

- Summer/ Winter system change-over

2 . Programmed Commands

-

automatic programmed commands w h i c h a r e scheduled by the

time of d a y , day of the week

- Sumrner/Winter t h e m o s t a t s e t t i n g

3 . Alarm Messages

-

o f f s t a t u s c o n d i t i o n of b i n a r y p o i n t s [ e - g . , o n l a f f ,

openlclosed, etc.)

-

o f f limit c o n d i t i o n o f analogue p o i n t s ( e - g . , temperature, humidity, pressure r e a d i n g s , e t c . )

4. Monitoring

- status condition of all p o i n t s

- analogue p o i n t values

- l o g g i n g of information on any p o i n t

5. Electric Dernznd Prediction

- provides an alarm when p r o j e c t e d demand exceeds a preset limit

6 . Electric Load Shed

- Automatic shedding o f selected l o a d s when dcmi~nd p r e d i c t i o n

indicates a need t o do so

7 . Miscellaneous

-

h e a t i n g and c o o l i n g plant monitoring

-

run time totalization f o r all motors connected to t h e CCMS

-

automatic restoration of a l l systems to t h e i r correct s t a t u s

ALARM FlXED HEAD 524 K WORDS CENTRAL CONSOLE IN SERVICES BLDE

I

T

I

1

r L 7 &R No.

3

I

f

I LOOP No. 1 I

I

-

I

I

!

LOOP N o . 2 1 JCAO CENTRAL COMPUTER SLIDE PROJECTOR LOOP REMOTES IN BUILDINGS C f l l 32 K CORE

*

REMOTE C.R.T. 625 CPS 4 REMOTE TELETYPE I PAPER TAPE READER LOCATED HEATING

I

F I G U R E A - l LOOP C.R.T. CONTROLLER A B L O C K D I A G R A M S H O W I N G THE C C M S O R G A N I Z A T I O N , U N I V E R S I T Y OF W E S T E R N O N T A R I O LOOP CONTROLLER

I

N o . 1 KEYBOARD N o . 2

1

t

4

I-

I---

4

-

1

-..

_{I hc Univers i ty of S ; ~ s k n t c l ~ c w n ~ ~ enmljus consists of c i g I ~ t c u n}

majar b u i l d i n g s ; i n Phasc 1 f i f t e e n of these b u i l d i r l g s a r e connected

to the central control and monitoring system. The total area s e r v e d

by the system is about 242,000 m2.

An c x t c n s i v e study was conducted to investigate the v a r i o u s

central c a n t r o l and monitoring systems t h a t could be used on t h e

university campus. A d e c i s i o n was made to install a Direct D i g i t a l

Control (DDC) system in 1982 to serve the entire campus. Figure 13-1

i s a block diagram outlining t h e structure o f the DDC system a t t h e U n i v e r s i t y of Saskatchewan.

[ a )

Central F a c i l i t y

T h i s consists of t h e C e n t r a l Corltrol 1;acilitp (CCF), Conimur~ication

l'raccssor (CP) , modcms, alarm and r e p o r t Loggers, opcr;itor t c r n ~ i i ~ : ~ l ;111d

~ r a l ~ l ~ i c J i s p l a y i 1 1 l i . t . I I - is ;I !>Loch Ji;r~r;~m s h u w i l ~ ~ t l ~ c c l v t ; ~ i 1s

of t h c c c n t r ; ~ l Fiicilit!..

( h ) BEen~ate I'rocessi~lg Units (RIW)

There is a RPU located in each building t o perform t h e r e q u i r e d

control strategies and t o communicate with t h e CCF. F i g u r e B-5 is a block diagram showing details o f a RPU.

The main f e a t u r e s of the KPU a r e :

-

It is capable o f stand-alone o p e r a t i o n and continues to perform l o c a l c o n t r o l funceians d e s p i t e failure of t h e CCF.

-

Control f u n c t i o n s a r e stared in t h e memory of the

RPU,

and dircctly

perform process monitoring, process analysis and control action

r e q u i r e d .

-

Data acquisition, i n v o l v i n g g a t h e r i n g and s t o r i n g c u r r e n t f i e l d

information Ear f u t u r e analysis, i s performed for each building

and can be shared w i t h o t h e r buildings through the central facility.

Central Control Functions

T h e s e f u n c t i o n s are r e l a t e d to a l l buildings on t h e campus and are

supcrviscd by t h e c e n t r a l computer.

I . Forward to building R P U ' s a l l processed informatian r e g a r d i n g

equipment shutdown s c h e u d l e s , weather data, cantrol acrions, and

a l l o t h e r o p e r a t o r f u n c t i o n s .

2 . Balancing t h e chilled water system to ensure t h a t each building on t h e campus g e t s i t s fair share of chilled water during t h e peak

3 . Implementing power deinand a r l n l y s i s and control progrsrt t a r a i n i m i :c t h e peak e l e c t r i c a l demnrtd. 'I'his is nchicvcd h!- c l t a ~ p i n ~ c l c c t r i c a l l o a d s ( f a n s , pumps, c t c . ) f o r prc-spccif ic.d pct-i wtli; o f

r

inir* u r ~ :$

rotational b a s i s nmottp, t h e b t ~ i l c l i t l g s .

4. At thc present timc, the CCMS is n o t r e q u i r e d to s t o r e long-tcrm

historical data. However, d a t a t r e n d s over l i m i t e d time frames a r e sampled and recorded every ten seconds.

5. A p r e v e n t i v e m a i n t e n a n c e program i s utilized to p r o v i d e weekly

print-out o f equipment/systems r e q u i r i n g maintenance i n the.

following week. The p r i n t - o u t sorts the maintenance items i n t e r -

nally by building areaizone and by equipment and i t s associated

maintenance f u n c t i o n . The program is capable o f performing o t h e r

functions r e l a t e d to equipment listing, trade-mark, and equipment

CCMS C E N T R A L C P C C F 4 WIRE COMMUNICATION LINE TO EACH OF THE l 5 RPU'S

-

University instolied 8 owned ) 50 AMP UNINTERRUPTABLE POWER SUPPLY CONDITIONER

;

FIRE HALL

1

:

'

I I L

- - - -

J L - - - - + - - - HEATING PLANT Cunrnunication$ Procc$sor Ccntral Cantrot Facility

I

-

OUTSIDE TRANSMITTER 411 HUMIDITY

SHORT HAUL MODEMS (Operating $peed

60I) b u d ) --

(Total of 18 _DISC

Trons.fiec. Units) _DRIVE DIGITAL I N

N o . 1 _lGHT

OPERATOR'S 5UPERVISOR1S PROGRAMMER

Dl SC - _{TERMINAL TERMINAL}

DRIVE TERMlNAl

No. 2

COMMUNlCATIONS

COMPUTER

T

16 K Core COMPUTER GdAPHlCS ALARM REPORT

DISPLAY LOGGER LOGGER

PDP 11/35

EXPANDER 96 K Corc

FIGURE 0 - 2

A B L O C K D I A G R A M S H O W I N G D E T A I L 5 OF THE C E N T R A L F A C L l T Y OF T H E D D C SYSTEM, U N l V E R I l T Y OF S A S K A T C H E I A N CAMPI:i

BOX PDP 11/35

_{- - - -}

_{- - -}

~ F I R E ALARM; ~ P E R A T O A ~ S ALARM-'

I

C C M S R E M O T E ( R e m o l e P r o c e s s i n g u n i t ) F I E L D D E V I C E S

I

S H O R T HAUL MODEnilS TEMP. T R A N S . HI SUMP LEVELS LO S T E W PRESS. (Opernting speed 600 b u d )

I

D I G I T A L I N P O I N T S

/

::'lNITl. AIR

(consists ol flying c a p c i t o r mux

AJP relectable & i n Amp)

A N A L O G O U T P O I N T S 4 (Opticaliy irolated) D I G I T A L O U T P O I N T S ---)i

1

VALVES o p n / s l a e

1

CURRENT TO PNEUMATIC TRANSDUCERS - CASSETTE

I

HUM. TRANS. PRESS. TRANS. 4

(

W A T C H D O G T I M E R I k R E M O T E COMPUTER I FIELD 1 -b MAINTENANCE

I

A

3

1-A N 1-A L O G IN P O I N T S 32 K Core PDP 11/05 1 CONSOLE TERMINAL 4 WIRE COMMUhlltATlON LINE TO CENTRAL COMPWTER hlniversily lnrtulled 8 Owned)

t

65 Points in Heolrh Science

4 0 Points in Library

35 P o k h in Health Science 24 Points in tibrory

118 Points in Heolttl 5 c i a n c ~ .

5 7 Points in Library

3b Points in Health Science 17 Pointr in Libwry

1

Processor

F I G U R E 8-3