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G o o d P r a c t i c e

Energy efficiency in higher education

buildings: condensing gas boilers

Condensing gas boilers for

heating in higher education

buildings

Run ning cost savings of 10-20

Paybacks under 5 years

High efficien cies using

conventional system design

Easy to install and maintain

Environmentally friendly

Overview

On average, higher education buildings use

a b o u t 3300 k wh i s t u d e n t p e r y e a r

o r

190

kWhlm2 per year in provid ing spac e

heat ing and domest ic hot water. This can

account for around 65% of the total energy

used in this type of build ing. Po tentially it is

one of the most controllable overheads in

any education budget. Overali responsibility

for saving energy, minimising environmental

dama ge and reducing expenditure, lies with

the directors of these establishments. One o f

the best ways to address these issues is to

install condensing g as b oilers. This results in

savings of 10-20

in

the annual fossil fuel

b i l l a n d a c o r r e s p o n d i n g r e d u c t i o n i n

harmful emissions to the a tmosphere.

On a nationai basis, heating and hot water

cos t s h igher educa t ion es tab l ishments

r o u g h l y

€ 6 0

m i l l i o n e a c h y e a r wh i c h

r e p r e s e n t s a l a r g e p a r t o f t h e i r t o t a l

expenditure on energy. If only one-third of

the existing boiler piant were to b e replaced

by condensing boilers then conservat ive

estimates indicate that this measure aione

would save

f

million each year. In general,

the necessary additional investment would

b e repa id in less than five years.

Ov e r a l l e n e r gy c o n s u m p t i o n i n h i g h e r

education resuits in around

2.2

million tonnes

of C O? being emitted into the atmosphere

every year, thus addin g to the greenhouse

effect. Of this, about 1 million tonnes can b e

attributed to sp ace hea ting and domestic hot

wate r . Us ing condens ing bo i ie r s cou ld

reduce this by 33

000

tonnesiyr and would

also help prevent acid rain

This technology provides

a

cost-effective way

of reducing pollution and conserving natural

resources. Examples of good practice using

condens ing bo i le r s in h igher educa t ion

buildings are discussed in this Case Study.

The results show that cond ensing boilers can

offer very attractive investment opportunities

in a wide range of circumstances.

HIGH SCHOOL YARDS

EDINBURGH

UNIVERSITY

Edinburgh University was founded in 1583

and its estate is made up mainly of Georgian

b u i l d i n g s a n d m o d e r n a i r - c o n d i t i o n e d

teach ing b lock s . The

to ta l

f ioor area is

400

000 m 2 a n d p r o v id e s f a c i l i t ie s f o r

over

14

000 students. This Case Study

represents a part of the Un iversity known as

the H igh School Yards com plex , This houses

t h e Ge o g r a p h y De p a r t m e n t w i t h a n

advanced computer centre, alongside the

Depar tment o f Den t is t r y , The bu i ld ings

prov ide teaching and research fac i l i t ies

i n c l u d in g s e m ina r r o o m s a n d l e c t u r e

thea t res , workshops , labora to r ies , and

offices for ab out

40

staff.

The c omplex consis ts of three bui ld ings

which vary between two and three storeys

forming a courtyard at their ce ntre. They are

all of heavyweight sandstone constructions

with pitched slate roofs and single glazed

wooden frame windows.

System

He a t i n g wa s p r e v io u s l y s u p p l i e d b y

two, very old. coal-fired, Lancashire steam

boi lers , each rated at 4000 lbs lhr . They

suffered from heavy emissions of soot and

were diff icult to control. This le d

to

a poor

m a t c h b e t w e e n o u t p u t a n d d e m a n d ,

result ing in high energy consumption. To

meet the demand, they were normally fully

manned and operated

24

hours a day.

To

improve ef f ic iency, the o ld d irect s team

Chemistry block eele Universiol

Oxford

Bmokes Universliy

ondensing boilers can

off r

very attractive investment

opportunities in a wide range of circumatances

E S T P R A C T I C E P R O G R A M M E

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R G Y E F F I C I E N C Y I N H I G H E R E D U C A T I O N B U I L D I N G S

C H O O L Y A R D S E D I N B U R G H U N I V E R S I T Y

T h e n e w c e n t ra l b o i l e r s we r e

1988. Three Atlantic

d e n s in g b o i l e r r a te d a t

kW

each. They have low

are particularly com pact.

ing a considera ble amount of space

old boiler room and co al storage area.

ilers were connec ted directly to ths

relation to the dem and for heat.

o v e r 4 8 0 0 h o u r s

1450

hours each,

s e r v a r i e s t h e c v e r a l l l e n g t h o f t h e

d each day , t hus m in im is ing

ed into two zones. These are controlled

ration is normaily

for 5 days per week from late

. However , t he

of cold w eather.

I l isted buildings. Consequent ly, a

d i lu ted f lue was

t o b l e n d w i t h th e s u r r o u n d i n g

T h i s wo u ld a l s o h a v e b e e n

c o n v e n t io n a l b o i l e r b e e n

l l y to r e s i s t t h e s l i g h t l y

sing boil er. Three separate 200 mm

The three fans are se quenced in

o

boilers operat ing. The condensate

last ic

. The bo i le r has an in tegra l s ta in less

e l t r ap t o p reven t combus t ion p roduc ts

onsumpt ion has drop ped f rom

700 kWh fo r t he o ld ins ta l la t ion t o

kWh with the new boilers; as a result

Energy Management

Br i tish Gas. The overal l

o n p r o g r a m m e h a s t h e r e fo r e

60

saving in fuel consumption.

s du e to an in tegra ted package o f

mproved controls and a combination of

boilers.

ginally anticipated a

4

years for the condensing

BALANCING

VESSEL

T

HIGH EFFICIENCY BOILERS

ICIENCY BOILERS

VESSEL

CONDENSING

BOILERS

EDIMENTATIONESSEL

Schemaflc

of

heating

syst m at

Hlgh School

Yards

Edinburgh Unlversify

boiler. This has been confirmed b y recent gas

consumpt ions , Based

on

overal i addi t ional

costs of

f 5500

and an est imated

10 fuel

saving due solely to the condensing boiler, the

actual payback is calculated at 4.6 years.

Reactions

The University Engineer originally decided to

install a condensing boiler to reduce running

costs and was closely involved in the design

and installation o f the new boiler plant. He is

therefore wel l p la ced to g ive a v iew

on

the

overall process. He feels that the design was

relatively straightforward and the installation

and commissioning proved to be very easy.

M a i n t e n a n c e i s s i m p l e a n d h e s a y s t h a t

there are no extra maintenance costs involved

w i t h c o n d e n s i n g b o i l e r s o v e r t h o s e f o r

non-condensing boilers. Reliabii i ty has be en

very goo d. He would definitely use condensing

boilers again in other bu ildings. Overall, the

Univers i ty s taf f are very p leased with the

r e l i a b i l i t y a n d p e r f o r m a n c e o f t h i s h i g h l y

efficient installation.

CHEMISTRY BLOCK KEELE UNIVERSITY

Founded as a college in 1949, Keele acquired

university status in 1962. The

400

acre campus

accommodates around 5500 students and is

s i t u a t e d n e a r Ne wc a s t l e u n d e r L y m e i n

Staffordshire. The site previousiy had three

extensive district heating schemes which were

phased ou t in the mid-198 0s to redu ce SyStem

losses. This provided an ideal opportunity to

introduce a range of energy efficient measures .

These inc luded eight separate plant rooms with

condensing boilers, one of which aiso has a

combined heat and power (CHP) unit.

This Good Practice Case Study focuses on the

boiler plant situated in the Chem istry blo ck

which supplies up to 3 MW of space heating to

eight major science buildings. n general, these

are

2-, 3-

and

4-

storey b uildings constructed in

the

1950s

and 60s with flat r w fs and extensive

single giazed areas. The system suppiies heat

to over 21 000 m2 of floor space in the Physics,

Geology, Biology. and Neuroscience buildings,

the C omputer Centre and the Chemistry block

Edinburgh Unlversifyboilers

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E N E R G Y E F F I C I E N C Y I N H I G H E R E D U C A T I O N B U I L D I N G S

C H E M I S T R Y B L O C K K E E L E U N I V E R S I T Y

itself. The bu ildings are m ainly laboratories and

lecture theatres with some staff office sp ace.

T h e y a c c o m m o d a t e u p t o 2000 s ta f f and

students. Occupancy is generally 5 days per

week f rom 08.30 to 19.00 with in termit tent

evening classes up to 21.00.

System

Three natura l-draught Broag Seagold GAS

6A-16HE gas-f ired condensing boilers were

installed in the Chemistry boiler house in the

summer of 1987 Each boiier has an output of

1013 kW and aii three supply space heating

only. Each boiier has a highiiow f ire facil i ty

s w i t c h e d b y a s e q u e n c e c o n t r o l l e r . T h i s

improves the efficiency by closely matching the

b o i i e r f i r i n g t o t h e d e m a n d f o r h e a t . As

recommended by Broag, all three boilers go to

low f ire before any are allowed to switch to

n ig h f i r e . T h e f i r i n g s e q u e n c e i s r o t a t e d

regularly to even out wear

on

the p lant. At the

time of writing, each of the boilers has run for

4 0 0 0 - 5 0 0 0 h o u r s a t l o w f i re a n d 7 5 0 - 8 5 0

hours at high fire. The reverse return primary

wa t e r c i r c u i t h a s b e e n k e p t a s s h o r t a s

possible in order to minimise heat losses. In

o r d e r t o m a x im is e s u m m e r h o t wa t er

efficiencies, domestic hot water (DHW) for the

Chemistry block is suppiied separately by two

direct fired s torage water heaters.

The heat ing systems are pr imariiy radiators

and natura l convectors but there is a lso a

mixture of m echan ical vent i la t ion systems,

radiant panels and uni t heaters. A cent ra l

wea ther compensa to r ac t s d i rec t ly on the

boilers to p rovide a coarse tempe rature control

in relation o the externa l temperature. There are

ten circuits to the buildings, some of which are

indiv idual ly cont ro l led by separate weather

compensators acting on three-port valves. This

provides f ine con trol on the radiator circuits,

and hence energy savings, whilst stili supplying

the somewhat higher temperatures necessary

for air heating and radiant panel system s. The

return water is therefore at a mixed tem perature

that is s t il l low enough to make the bo i lers

conden se for much of the year.

Each boiler has a condensate drain made of

standard plastic waste p ipe with a trap to avoid

combustion products discharging into the plant

room. There is also an insp ection point to allow a

visual check

on

the level

of

conden sate. The flue

system combines in the boiler room to form a

single vertical chimney which is more compact

than tha t f o r conven t iona l bo i le r s . I t IS

cons tructed of twin wall stainless steel in order to

resist the m ild ac idity of any conde nsate which

may form in the flue. The flue has a separate

condens ate drain to accom modate his.

Economics

The Chemistry block boiler house installation

was designed by the Maintenance Manager

and i t is operat ing to h is expectat ions. His

or ig ina l es t imate o f a th ree year p ayb ack

period has been confirmed. With a current gas

c o s t n o w u n d e r € 3 2

000

p e r a n n u m , t h e

additional cost of the condensing boilers has

been paid back in just over three years. The

payback would have been even quicker had

the third boiler, which is only required for peak

lo a d s , b e e n c o n v e n t io n a l p i a n t . A mix of

condensing and convent ional boi lers would

have significantly reduced the capital cost of

t he ins ta l la t ion re su l t ing in on ly a sma l l

reduct ion in ef f ic iency, thus improving the

payba ck. The savings of f550 0 eac h year now

g o b a c k i n t o t h e Un i v e r s i t y ' s b u d g e t f o r

additional expenditure.

Ructlons

T h e M a i n t e n a n c e M a n a g e r h a s m a d e a

conscious effort to introduce energy efficiency

at every opportunity. This has also included

zone control, weather compensation and CHP.

He is very sat isf ied with all the condensing

boiler installations

on

the site and would always

seek to use them in the future. Installing an d

commiss ion ing t hese bo i le r s was

no

more

complicated than for conventional plant and he

h a s g e n e r a i ly f o u n d t h e m t o b e e a s y t o

maintain with no extra cost implications. The

eight separate condensing boiler plants on site

have all proved to be very reliabie - especiaily

the Chemistry block boilers.

OXFORD BROOKES UNIVERSITY

The Oxfo rd Brookes Unive rsity, formerly Oxford

Polytechnic, can trace its origins back to 1865

when it was a schm l of art. In 1976 it amalgamated

with a teacher training college based at Wheatley

and is now located

on two

sites.

The main Gipsy Lane Campus in Headington

was built between 1953 and 1975 whereas the

Wheatley Campus, situated 5 miles away, was

buiit between 1974 and 1988. The University

has abou t 1500 s ta f f se rv ing over 11 000

students, Many of the teaching facil it ies an d

res idences a re used ou t o f t e rm t ime fo r

external conferences, and teaching often goes

on un tii 21 OO throughout the whole of the yea r,

In recent years it bec ame d iff icult to m aintain

t h e s p r a w l i n g m a i n s of t h e c e n t r a l i s e d

h e a t i n g s y s te m a n d e n e r g y c o n s u m p t i o n

was high due to losses from the system. A

cent ra i theme throughout a progra mm e of

decentralisat ion, which began in 1990, has

been the instaliation of over 119 conde nsing

boilers in 14 plant rooms at Wheatley Campus

a n d 1 7 p ia n t r o o m s a t t h e G ip s y L a n e

C a m p u s . T h e D e p u t y B u i l d i n g s O f f i c e r

Keele University boilers

responsible for energy management instigated

the decentralisation in order to red uce energy

costs. He carr ied out the design

1

the new

systems himself, with support from the boiler

s u p p l i e r s . He i s

so

p l e a s e d w i t h t h e

conde nsing boilers that work is in progress to

instali 30 more in halls of residenc e.

System

Space is at a premium on the sites and this is

jus t on o f t h e r e a s o n s why t h e c o m p a c t

Microstar boilers were chosen.

In

some cases,

this avoided buiiding new plant rooms as part

of the decentraiisation, keeping capital costs to

a minimum.

The boilers are installed in a wh ole range of

building types including eaching block s, student

accom moda t ion, comm on rooms, a laundry

b loc k and a bus iness cen t re . Many o f the

residential blocks have, for exa mple, eight wall

hung 20 kW gas-fire d Yorkpark M icrostar boilers.

All the heat ing systems are controlled by a

centrai building energy m anagement system

(BEMS). This a l lows c lose m onitor ing, t ight

control and, ukimately, improvements in comfort

cond i t ions and reduc t ions in energy

consumption andlor costs. This is directly linked

to monitor ing an d target ing sof tware which

allows a whole range of soph isticated ech niques

including trend log ging a nd regression analysis.

There are numerous gas and electricity meterS

ins ta l led ac ross t he s i t e in order t o a l low

invoicing for conferences and seminars. This

also allows the estates staf f to keep a close

watch on consumption trends in order to identity

any problems very quickiy.

Each plant room has an opt imum start istop

control set in order to meet the requiremen ts of

the teaching staff. Sequence control m atches

the boiler firing to the load, essentially making

each p lant room one large modular boi ier

system. Each of these is weather compen sated

which reduces the return water temp erature

when the outs ide temperature is mi id. This

overall energy saving co ntrol package, resulting

in h igher o perat ing ef f ic ienc ies, makes the

boilers condense in the m ilder months of Spring

and Au tum n, Further con t ro l o f t he spa ce

temperatures is achieved using zone valves

throughout each b uilding . The new hot water

systems in the student accommodation blocks

have high cap acity ca lorifiers which ensure that

heat up t imes are very fast , This general ly

provides low return water temperatures an d

thus increase d efficiencies

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G Y E F F I C I E N C Y I N H I G H E R E D U C A T I O N B U I L D I N G S

Overcost Approxlmate

stlmated annual Estlmaied annual Estimated

runnlng cost runnlng

cost

saving

percentage

(condensing payback period

(conventional system)

(condensing element) savlng

element) (condensing element)

f

%

f

years

11 900 1200

1 5

500

4 6

Yards

UnlvenlN

37 100 5500 15

block,

University

8

700 1370

16

dord

Brwkeo

C block)

ed economlcs of the condensing boiler lnstallatlons compared to new

all

convenilonal systems, the original plant havlng come to an

of

its useful ife. In all cases savlngo are quote on the bads

of

he same useful heat delivered to the bulldlng, le room temperatures are

d savings shown take Into account system design factors.

y of the bo ilers have b alanced flues

e this has not be en prac t ical,

d, Conde nsate drains are run in ordinary

c was te p ipe and each bo i le r has an

ish to allow a visual inspe ction of the flow of

- a prime indication of high efficiency.

has achieved m ajor savings due

ramm e of decentralisation and the

im p r o v e m e n ts i n c o n t r o l . T h e

sing boilers have been a key p an of this

3 and

5

years.

The residential blocks have higher

nd there fo re a be t te r payback

years. Conside ring this is a relatively low

inves tment and in l ine w i t h p rev ious

It seems highly likely, therefore.

under two years.

tralising he main boiler plant meant that the

d as general boiler maintenance staff. This

o a high level. Standardisation of plant

lped this and has redu ced the spares that

need to be retained. The University's Deputy

Buildings Officer commented that there is no

additional maintenance compa red

to

conventional

plant, particularly if staff are trained p roperly.

Good training leads

to

better maintenance which

directly improves energy efficiency and relia bility

The decision to install a further 30 condensing

boilers in halls of residence indicates both the

success of the plant and the satisfaction of the

estates staf f . They maintain that the lack

of

complaints about hea t ing combined with low

g a s c o s t s s h o ws ju s t h o w w e l l th e p l a n t

performs. They are expecting between 10 and

15 years life from the boilers which is about the

same as conve ntional plant.

CONCLUSIONS

These three Case Studies have shown that

conde nsing boilers are a viable proposition in

h ig h e r e d u c a t i o n b u i l d i n g s . T h e y h a v e

prov ided energy savings of 10.16 and simple

payback periods of

3 5

years, All the eng ineers

c o n c e r n e d a r e h a p p y a n d w o u l d i n st a ll

condensing boilers again. They have proved to

be reliable and econom ic whilst m aintaining

comfortable conditions in the range of bu ilding

types and uses on these university campuses.

CI S€

Manual

Further

Information

This Good Practice Case Study is one of a

series on the use of condensing boilers in

var ious b ui ld ing sectors. Good Pract ice

Guide 16 provides practical information

on

i ns ta l l ing condens ing bo i le r s in la rge

bui ld ings. The Char tered Inst i tu t ion of

Bu i ld ing Serv ices Eng ineers (CIBSE)

Appl icat ions Manual AM31 Condensing

Bo i le r s g ives de ta i led gu idance

on

al l

aspects of the subject. This covers app liance

selection, new application yardsticks, system

design and ew no mi c evaluation.

The information presented in this series of

Case Studies has been taken from ma terial

provided by the users and from site visits

carr ied out by independent consultants.

Where possibl e, econom ic f igures have

b e e n c a l c u la t e d f r o m t h e f u e l b i i l .

Estimates have been made in cases where

these were not available. The co-operation

of the owners, designers, managers and

occupants of the Case Study buildings is

gratefuily acknowledged.

further

sop** 1

lhls

or

Other B e d PracIIce programme publications please sonmu BRECSU and ETSU.

projects:Enquilfes

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Building R-mh Emb llshm enl, Garslon,

Watford, WD2

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923

€64787.

Induslrlal

pmleca:

Energy

Eflldmcy EnqYilfes Bureau, ETSU, HaWY.11

OxbrdSh lR OX11

ORA. Tel0235 436747.

T h x 83135. FBX 0235

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