Baxi BOSTON 70 OF User guide

BAXIBOSTON
ALLMODELS
FLOORSTANDINGOPENFLUE(OF)
CENTRALHEATINGBOILERS
INSTALLATIONANDSERVICINGINSTRUCTIONS
GASTYPEG20(NaturalGas)
BAXIBOSTON80OFG.C.No4107765
BAXIBOSTON70OFG.C.No4107764
BAXIBOSTON60OFG.C.No4107763
BAXIBOSTON50OFG.C.No4107762
BAXIBOSTON40OFG.C.No4107761
PleaseleavetheseInstructionswiththeUser
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InstallationInstructions
INTRODUCTION
ThisisarangeofFloorStandingOpenFlueBoilers.Thereisachoiceofoutputslistedbelow:
BOILERTYPE HEATOUTPUT
 kW Btu/h
80OF 20.8to23.4 71,000to80,000
70OF 17.8to20.5 61,000to70,000
60OF 14.9to17.6 51,000to60,000
50OF 12.0to14.7 41,000to50,000
40OF 9.1to11.7 31,000to40,000
Theboilersshareacommonoutercasewithinwhichthereisadequatespacetofitacentral
heatingpumpusingstandardfittings.
AllappliancesaredesignedforuseonGasTypeG20(NaturalGas)only,atsupplypressure20
mb.
Eachapplianceconsistsessentiallyoftwocomponents,namely:
1.COMBUSTIONCHAMBERwithheatexchanger,burnerandcontrols.
2.OUTERCASE.
InstallationRequirements
GENERAL
TheinstallationmustbecarriedoutbyacompetentinstallerandbeinaccordancewithrelevantBS
CodesofPractice,I.E.E.Regulations,GasSafetyRegulations,BuildingRegulationsandbylaws
oftheLocalWaterUndertaking.ReferencesshouldbemadetoBS6891,BS6798,BS5440Part1
&2andBS5449.
SITING
Theseappliancesmustbefittedonasuitableoutsideorinsidewallwithdueconsiderationsofthe
openfluerequirements.
TheyshouldNOTbeinstalledinabathroom,bedroomorbedsittingroom.
Aneworexistingcupboardorcompartmentusedtoenclosetheboilermustbeconstructed
specificallyforthispurpose.
DetailsofessentialfeaturesofcupboardcompartmentdesignaregiveninBS5440:2.
CLEARANCES
Theminimumverticalareasrequiredfortheappliancesdependontheapplianceratingandits
application.Thedetailsaregiveninfig5.

WorkTops
AboveBoiler(AllModels) 100mm(4in)Min
Sides SeeFig5
VENTILATION
DetailedrecommendationsforairsupplyaregiveninBS5440:2.
Thefollowingnotesareintendedtogivegeneralguidance.Theroominwhichtheopenflueunitis
situatedrequiresanairventwhichshouldbedirecttooutsideortoaroomwhichitselfhasanair
ventdirecttooutside.Wheretheboilerisinacompartmentwithairventsdirecttooutsidetheroom
containingthecompartmentdoesnotrequiretheprovisionsofadditionalventilation.
APPLIANCE MINIMUMFREE
 AREAOFAIRVENT
cm2in2
80OF 102 16
70OF 84 13
60OF 74 11.5
50OF 57 9
40OF 39 6
Theactualminimumeffectivearearequirementsofcupboard/compartmentairventsarebased
upontheratedinputoftheappliance.
Ventilationareasrequired:
APPLIANCE HIGHLEVEL
VENTAREA
LOWLEVEL
VENTAREA
  cm2in2cm2in2
80OF Compartment 271 42 542 84
70OF ventedto 232 36 464 72
60OF adjacent 212 33 423 67
50OF room 176 27 353 55
40OF  140 22 281 44
80OF Compartment 136 21 271 42
70OF ventedto 116 18 232 36
60OF outside 106 17 212 33
50OF building 88 14 176 27
40OF  70 11 140 22
FLUEARRANGEMENT
The80,70OFareintendedforconnectionwith125mm(5in)fluetube.The60,50and40OFare
intendedforconnectionwith100mm(4in)fluetube.
ForfullinformationonfluesrefertoBS5440,butthegeneralrequirementsareasfollows:
1)Theflueshouldbekeptasshortandaswarmaspossible.
2)Givemaximumpossibleverticalrisefromtheappliancebeforeusinganybends(preferablyat
least600mm(24in)).Avoidtheuseofrightangledbends.

3)Terminateinanapprovedterminalpreferablyaboveridgeheightbutatleastabovetheeavesof
apitchedroof.
4)IfTwinwalltypefluetubingistobeusedtheinnertubingoftheboileradaptormustnotproject
intothedraughtdiverteroftheboiler.Aboileradaptorwhichmeetsthisrequirementisobtainable.
5)Anexistingbrickchimneyshouldbelinedwithacidandmoistureresistantmaterialssuchas
stainlesssteelflexiblefluepipe.Thisisparticularlyimportantiftheflueisabove6.5metres(20ft)
inheightandnotwhollyinternal.WHETHERORNOTTHECHIMNEYISTOBELINEDITMUST
BESWEPTTHOROUGHLYBEFORETHEINSTALLATION.
6)Whatevertypeofflueisuseditmustbeproperlysupportedandnotsimplysupportedonthe
boiler.
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WATERCIRCULATIONSYSTEMS
(seepages8&9)
Theappliancesareonlysuitableforconnectiontoacisternsupplyandcanbeusedwith:
1)Pumpeddomestichotwaterandpumpedcentralheatingsystems.
2)Gravityflowdomestichotwaterandpumpedcentralheatingsystems.
(a)With28mmpipestheminimumcirculatingheadforgravitydomestichotwatershouldnotbe
lessthan1metre(3ft3in)measuredverticallyfromtheflowconnectionontheboilertotheflow
connectiononthecylinder.Atthishead,themaximumhorizontaldistancemeasuredalongtherun
ofthepipeshouldnotexceed3metres(10ft).Greaterhorizontaldistancesandsmallerpipesizes
areacceptablewithsuitablyincreasedheads.Allowancesmustbemadeforpipebendswhere
necessary.
(b)Iftheaboveconditionsarenoteasilymetthenpumpedprimariesshouldbeused.
(c)Gravityflowandreturnpipesshouldbelaidtomaximumfalltoavoidairlocks.
Thefollowingpointsareofparticularimportance:
1)THEWATERSPREADERMUSTBEFITTEDTOTHEPUMPEDRETURNCONNECTIONON
ALLSYSTEMS.
2)Theappliancesmustnotbeusedonsealedsystems.
3)Thesystemmustbedesignedtoavoidreversecirculation.
4)Thestaticheadmustnotexceed30metres(100ft)ofwater.
5)Theboilersmustonlybeusedwithanindirectcylinderwhendomestichotwaterisrequired.
6)Drainpointsshouldbefittedatthelowestpointsinthesystem.
7)Thesystemmustbedesignedsuchthatgravitycirculationintheheatingsystemdoesnottake
placewhenthepumpisnotrunning.
GASSUPPLY
ThegasconnectionislocatedatthebottomlefthandsideoftheapplianceandisRC1/2(1/2in
B.S.P.T.internal).Ensurethatthepipeworkfromthemetertotheapplianceisofadequatesize.Do

notusepipesofasmallersizethantheappliancegasconnection.
ELECTRICALSUPPLY
ExternalwiringmustbecorrectlyearthedandpolarisedandinaccordancewithI.E.E.Regulations.
Forwiringinstructionssee'ElectricalConnections'.
APPLIANCEDETAILS(allmodels)
HEIGHT 900mm(351/2in)
WIDTH 395mm(151/2in)
FORWARDPROJECTION 
FROMTHEWALL 535mm(21in)
BOILERTAPPINGS 4xRp1(1inBSPinternal)
and 
 1xRp3/4(3/4inBSPinternal)
ELECTRICALSUPPLY 240v~50Hz3ampfuse
GASCONNECTION Rc1/2(1/2inBSPTinternal)
MAX.WORKINGHEAD 30m(100ft)
THERMOCOUPLEOUTPUT 1015mv
APPLIANCE WEIGHTEMPTY WATERCONTENT
80OF 98kg 7litres
70OF (216lbs) (1.54gallons)
60OF  
50OF 79.2kg 5.1litres
40OF (174.6lbs) (1.12gallons)
HYDRAULICRESISTANCECHARTS

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FittingtheAppliance
PREPARATION
1)AsoundandlevelfloorwhichconformstotherequirementsoftheLocalAuthoritiesandBuilding
Regulationsmustbeprovided.
2)Selectthemostsuitablepositionfortheboilertakingdueaccountofanyclearancesrequiredfor
thesafeandproperfunctionsoftheboileranditsassociatedcontrols.

3)Manoeuvretheboilerintopositionsothatthetwospacerpipsontherearofthedraughtdiverter
touchthewall.
4)Connectthewaterflowandreturnpipes(seeBoilerConnections).
5)Connectthefluepipe,makingsurethatthefluetrimisplacedinpositionbeforethefinal
connectionismade.
6)Partiallyfittheoutercase.
7)Connecttheelectricalsupply(seeElectricalConnections).
8)Completetheinstallation(seeCommissioningtheUnit).
9)Completetheassemblyoftheoutercase.
BOILERCONNECTIONS(Fig3)
Theboilershave5waterconnections:
2xRp1(1inBSPinternal)returnconnections.
2xRp1(1inBSPinternal)flowconnections.
1xRp3/4(3/4inBSPinternal)flowconnection.
The1xRp3/4(3/4inBSPinternal)flowconnectionisforusewhenthepumpisfittedinsidethe
outercase.Forotherinstallationsthisconnectionmustbeplugged.THEWATERSPREADER
MUSTBEFITTEDTOTHEPUMPEDRETURNCONNECTIONONALLINSTALLATIONS.THE
MARKSONTHESPREADERMUSTBEBETWEENTHETWOMARKERSONTHE
COMBUSTIONCHAMBER(Fig4).
Thespreaderhasonemarkonthe80,70andhastwomarksonthe60,50,40.
Wheninstallingthepipeworkensurethat:
a)Suitableunionfittingsareusedatthefirstjointofallboilerconnections.
b)Thepipeworkwillrunthroughthecutoutsprovidedintheoutercase(Fig2).
c)Drainoffpointsareprovidedasappropriate.
d)Pipesizesaresuitableforthesystemdesign.
Pump(Fig1)
Asuitablepumpe.g.GrundfosSelectric4orSMCCommodorewithballtypeisolatingvalvesand
22mmcompressionfittingsmaybefittedinsidetheoutercase.
Thepumpshouldbeconnectedtothe3/4inflowconnectiononthefrontoftheheatexchanger
usingthefollowingstandardfittings.
A 1off Elbow3/4BSPmalex3/4BSPfemale
B 1off Conexstraightconnector3/4BSPmale
  x22mmcopper
C 3off 22mmYorkshireelbows
D 1off wheninstallingthe60,50and40
  60mmlong22mmcoppertube
D 1off wheninstallingthe80and70
  92mmlong22mmcoppertube
E 1off 100mmlong22mmcoppertube

F 1off 145mmlong22mmcoppertube
G 1off 42mmlong22mmcoppertube
Theredundantflowconnection(s)mustbeplugged.
Accuracyisimportanttoavoidthepumpandorpipeworkobstructingremovalofthetoppanelof
thecombustionchamber,orfoulingthetoppaneloftheoutercase.
OUTERCASE(Fig6)
Assembletheoutercaseinthefollowingmanner:
1)LocatetheRHsidepaneloverthepegsattheRHsideofthebaseandpressdownwardsto
secure.Whenfittingthepanelsifaccessisrestrictedthecutoutsatthetopofthebackedgeofthe
panels.canbeusedtopassthecasefixingbrackets.
2)Securethepaneltothecasefixingbracketswithtwoofthesixscrewsprovided.
3)Repeat1&2withtheLHsidepanel.
4)Securethehingesofthefaciapaneltothetwosidepanelsusingtwoofthesixscrewsprovided.
5)Atthispointtheelectricalconnectionstothefaciapanelcanbemadeandtheappliancecanbe
commissioned.(See'ElectricalConnections'and'CommissioningtheAppliance').
6)Swingthefaciapanelupwardsandsecuretothesidepanelsusingthetwoscrewsretainedto
thecontrolfacia.
7)Lifttrimclearofflueconnectionontheboilerandlocatethetoppanelonthetopoftheside
panelsandpressdowntosecure.Repositionthetriminthecutoutonthetoppanel.
8)Hookthebottomedgeofthefrontpaneloverthelugsonthebaseandswingthetopedgeback
tillthepegsatthetopofthepanellocateinthecorrespondingholes.Presstosecure.
GASCONNECTION(Fig3)
Adaptthegassupply15mm(1/2inBSP)withintheoutercasemakingthegasconnectiontothe
servicetapprovided.

fig1PumpinCasing
Page5
fig2OuterCase

fig3BoilerConnections
Fig4SpreaderinPumpedReturnConnection
fig5ClearancesWorkTops

fig6OuterCaseAssembly
Page6
ElectricalConnections
THISAPPLIANCEMUSTBEEARTHED
GENERAL
Themainssupplyrequiredis220/250v~50Hzfusedat3amps.Adoublepoleswitchshouldbe
providedintheinstallationoranunswitchedsocketoutletshouldbeused.Allexternalwiringshall
becorrectlyearthedandpolarisedandbeinaccordancewithI.E.E.Regulations.
Electricalsupplytocontrols
Therecommendedcableforconnectiontotheapplianceis0.5sq.mm16/0.20PVCheatresistant
gradetoBS65001990.
Theinputcableshouldbesecuredwiththecableclipsprovidedandbelaidtoavoidcontactwith
hotsurfaces.
Thelengthofthesupplyconductorsbetweenthecablegripandtheterminalsmustbesuchthat
thecurrentcarryingconductorsbecometautbeforetheearthingconductorifthecableshouldslip
outofthecablegrip.

1)Withtheoutercaseassembledasin'OuterCase'14removethe2screwssecuringthe
thermostatcovertothefaciapanel.
2)Fittheinputcabletotheterminalstripandclampusingthecablegripprovidedandclampthe
incomingcableintothecableclipsprovidedontheoutercasesidepanelsoastoavoidcontact
withthehotcombustionboxsurfaces.
3)Connectthe2greenandyellowearthwireshalfwaydowntheappliancewiringharnesstothe
combustionchamberearthpointontheoutercasesupportbracket.
4)Fitthesocketattheendofthewiringharnesstotheplugattachedtotheburnerfeedpipeand
clipthewiretothecableclipsprovided.
5)Refitthethermostatcovertothefaciapanel.
6)Pushthethermostatphialintothethermostatpocketandclipthecapillarybehindtheretaining
clip(Fig8).
INTERNALWIRING
ProgrammerWiringPlate

Page7
NotesforGuidance
PIPESIZING

a)Thesizesofflowandreturnpipesfromtheboilershouldbedeterminedbynormalmethods
accordingtotherequirementsofthesystem.Normallythepumpshouldbesettogivea11°C(52
°F)dropacrossthesystemwiththegasrateoftheboileradjustedtotheoutputrequired.
b)Theopenventpipemustbeaminimumof22mmandmustrisecontinuouslytoabovethefeed
tank.Theflowpipefromtheboilermayformpartoftheopenvent.Nopartoftheopenventshould
containavalve.
c)Inafullypumpedsystemthecoldfeedpipe(15mm)maybeconnectedtotheflowpipe,6ins
awayfromtheventpipe,buttheremustalwaysbeacoldwaterpathtotheboilersreturn
connection.
DOMESTICHOTWATER
Anindirectcylindermustbeused.Ifaselfprimingindirecttypeisemployeditmustbeofadequate
sizeandappliedstrictlyinaccordancewiththecylindermanufacturer'sinstructions.
FUELECONOMY
Betterfueleconomyisachievedbyexercisingcontroloftheboilerbymeansofaroomthermostat
andoracylinderthermostatasappropriate.Examplesofdifferentcontrolsystemsaregivenbelow
alongwiththeappropriatewiringdiagrams.
ALLOWINGTHEBOILERTOCYCLEONTHEBOILERTHERMOSTATDOESNOTPRODUCE
THEBESTRESULTS.SIMILARLYFORECONOMYANDBOILERPERFORMANCETHE
SYSTEMSHOULDBEDESIGNEDSOTHATGRAVITYCIRCULATIONINTHEHEATING
CIRCUITDOESNOTTAKEPLACEWHENTHEPUMPISNOTRUNNING.
ControlSystems
FULLYPUMPEDSYSTEMS
OneZoneValve(Fig.A)
ZonevalvewithauxiliaryswitchfittedatpointV.Acylinderthermostatandaroomthermostatare
usedtocontrolboththepumpandtheboiler.Theroomthermostatalsocontrolsthezonevalveto
stopwatercirculationintheheatingsystem.
TwoZoneValves(Fig.C)
ZonevalvesarefittedatpointsVandUtostopwatercirculationtotheheatingsystemandthe
cylinder.Thevalvesarecontrolledbyaroomthermostatandacylinderthermostatrespectively,
eachofwhichalsocontrolstheboilerandthepump.
DiverterValve(Fig.D)
AdivertervalveisinsertedatpointWtodirectwatercirculationtoeitherthecylinderortheheating
system.Thevalvealongwiththepumpandtheboileriscontrolledbyacylinderthermostatanda
roomthermostat.
GRAVITYD.H.W.SYSTEMS
SundialControl(Fig.B)
Boththeboilerandthepumparecontrolledbyacylinderthermostatandaroomthermostat.The
roomthermostatoverridesthecylinderthermostatwhenheatingiscalledfor.



Inbothcasesthecoldfeedpipewhichistheneutralpointofthesystemisshowndirectlybehind
thepumptoavoidsubatmosphericpressure(airentrainment)inthesystem.

Page8
FigAOneZoneValveFullyPumpedSystem

FigBSundialGravitySystem

FigC2ZonesValveFullyPumpedSystem

FigDDiverterValveFullyPumpedSystem
Page9
CommissioningtheUnit
Flushthewholesystemwithallvalvesopen.
Fillthesystem,venttheradiatorsandcheckforwaterleaks.
TurnthegasservicetaptotheONposition,checkforgassoundness(BS6891:1988).Purgethe
airfromthegassupplypipeatthegasservicetap.
TurntheboilerthermostattotheOFFposition.
Turnonthemainselectricalsupplyandensurethatallexternalcontrolse.g.roomthermostat,
timer,etc.,arecallingforheat.
Removetheburnerpressuretestpointscrewandconnectapressuregauge.
HoldinthegreyON/OFFbuttononthegascontrolvalve(Fig7).Pressthepiezounitbutton(Fig7)
andrelease.Repeatuntilpilotlights.HoldinthegreyON/OFFbuttonforafurther20secondsand
thenrelease.Thepilotlightshouldthenstayalight.(IFTHEPILOTFAILSTOREMAINALIGHT
TURNTHEGREYON/OFFBUTTONCLOCKWISE,WAIT3MINUTESANDSTARTAGAIN

FROMTHEBEGINNINGOFTHEPARAGRAPH.)Theflameshouldbewithoutayellowtipandbe
approximately25mm(1in)long.Noadjustmentofthepilotflameisnecessaryaswiththerestrictor
screwfullyopenthepilotjetissizedtogivethecorrectflamelengthat20mbar(8inwg)inlet
pressure.
Operatetheburnerbyturningthethermostatknobtothehighsetting.CHECKTHEOPERATION
OFTHEFLAMEFAILUREDEVICEbyturningthegreyON/OFFbuttonclockwise.Theburnerand
thepilotshouldgoout.
TurntheboilerthermostattotheOFFposition.Wait3minutesandrelightthepilot.
Operatetheburnerbyturningthethermostatknobtothehighsetting.
Removethecoverscrewandadjusttheappliancegovernortogivethecorrectpressure
correspondingtotherequiredinput.Seetableopposite.Checkthispressureafter10minutesand
adjustifnecessary(Fig7).Replacecoverscrew.
TurntheboilerthermostattotheOFFpositionandrecheckthepilotflamelength.
Thesystemshouldnowbeflushedagainwhilsthot,refilled,ventedandcheckedforwaterleaks.
Makeafinalcheckforgassoundness.
Replacetheburnerpressuretestpointscrewandthenturntheboilerthermostattotherequired
setting.
Completetheassemblyoftheoutercaseasdescribedin'OuterCase'(Fig6).
Instructtheuserintheuseoftheunit.Pleaseleavetheseinstructionswiththeuser,alongwiththe
user'sinstructionsandsafetycard.
NOTE:Intheeventofanelectricalfaultaftertheinstallationoftheappliance,preliminaryelectrical
systemchecksmustbecarriedout(i.e.Earthcontinuity,polarityandresistancetoearth).
Model Maximum
Input
Setting
Pressure
Minimum
Input
Setting
Pressure
80OF 30.36kW 15.8mbar 27.11kW 12.7mbar
 (103600Btu/h) (6.35inwg) (92500Btu/h) (5.1inwg)
70OF 26.4kW 16.4mbar 23.15kW 12.2mbar
 (90100Btu/h) (6.6inwg) (79000Btu/h) (4.9inwg)
60OF 22.91kW 16.8mbar 19.5727kW 12.3mbar
 (78200Btu/h) (6.7inwg) (66800Btu/h) (4.9inwg)
50OF 19.25kW 17.1mbar 15.91kW 11.7mbar
 (65700Btu/h) (6.85inwg) (54300Btu/h) (4.7inwg)
40OF 15.26kW 16.9mbar 12.07kW 10.5mbar
 (52100Btu/h) (6.8inwg) (41200Btu/h) (4.2inwg)

fig7BurnerControls
fig8BoilerThermostat
Page10