Weil-McLain SlimFit 3 Series User guide

Part No. SF-E009-A/0516
Application Guide
for
Common Venting SlimFit 550-750 Series 3 Boilers
Hazard denitions
e following dened terms are used throughout these Instructions to bring attention to the presence of hazards of
various risk levels or to important information concerning the life of the product.
Indicates presence of hazards that can cause severe personal injury, death or substantial property damage.
Indicates special instructions on installation, operation or maintenance that are important but not related
to personal injury or property damage.
Common Venting methods and requirements for SlimFit Boilers (SF 550 and SF 750 Series 3)
The SlimFit boiler can be common vented when the following requirements are met.
• CommonventingoftheSlimFitboilercanonlybedoneinaCategoryIIventsystem.Allrequire-
ments for the SlimFitboilertobeventedinaCategoryIIcongurationmustbemetasstatedinthe
SlimFit Boiler Manual or all subsequent addendas.
• SlimFit boilers can only be common vented with other SlimFit Boilers.
• ThemaximumnumberofSlimFit boilers to be common vented together is eight.
• TheVentsystemforaCategoryIISlimFit boiler is considered a Designed / Engineered vent system
and should be designed by a professional using accepted engineering practices.
• VerticalVentonly.
• Combustionairmustcomefromtheboilerroom.SeeDirectExhaust–CombustionAiropening
requirements in SlimFitVentCategoryIIAddendum.
• Mustincreaseventingto6”or8”usinga8”to6”bellreduceratboilerventadapterforCategoryII
VentConnection.
• TheVentSystemshouldbedesignedsothatthepressureintheverticalventpipeisbetweenthe
ranges provided in the Table 1, page 2, during all operating conditions (i.e., High Fire through Low
Fire,prepurge,postpurgeandignition).Ifanegativepressurecannotbeguaranteedatprepurgeand
post purge, a backflow preventer is required on each boiler’s vent.
To prevent backflow through boiler, negative pressure must be maintained in vent system at all
times including prepurge and post purge cycles.
• Fluegastemperatureshouldnotexceed210°F;theboilerwillshutdownandrecycleifitdoes.The
uegastemperatureshouldtypicallybewithin20°Fofthereturnwatertemperatureoftheboiler.If
there is the potential for a wide variation in return water temperatures, the lowest possible tempera-
ture should be used for any calculations.
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®
Series 3
Models 550 and 750 MBH
Commercial Condensing
Gas-fired water boilers

SlimFit™Series 3 gas-fired water boiler — Application Guide
Part number SF-E009-A/0516
2
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• Stack/VentFlowRateforeachindividualboilermodelislistedinthetablebelow.Thisowrateis
basedontheunitrunningat9.25%CO2andthemaximumuegastemperatureof210°F.
The values can vary depending on the location of the installation and operating conditions.
• Acarbonmonoxidedetector(s)isrequiredintheboilerroomforSlimFitboilersinstalledinaCat-
egoryIIconguration.Thecarbonmonoxidedetectormustbewiredonthesameelectricalcircuitas
theboiler.Checkyourlocalcodesforanyadditionalrequirementsofcarbonmonoxidedetectors.
ImproperInstallationofaCategoryIIventsystemresultinginpositivepressureintheventsystemcan
resultinuegasspillageandcarbonmonoxideemissions,causingseverepersonalinjuryordeath.
Weil-McLainrecommendstheuseofaVariableSpeedChimneyFan/Powerventertoensurethatthe
appropriatenegativepressureismaintainedforCategoryIIventing.Thisisrecommendedbecause,asa
resultoftheboiler’sefciency,theexhaustgastemperaturescanbequitelowresultinginlessnaturaldraft.
AowprovingswitchshouldbewiredintotheProofofClosurejumpercircuitontheboilercontrol.See
the boiler manual for additional information. The use of this device should be considered in any Engi-
neeredVentsystem.
 Weil-McLainrecommendstheuseofaDoubleActingBarometricDamperorModulatingDampertoen-
suretheappropriatenegativepressurerangeiskeptforCategoryIIventing.Theuseofthisdeviceshould
beconsideredinanyEngineeredVentsystem.
 Whenusingadamperofanykind,itisrecommendedtouseathermalspillswitchtodetectanyexhaust
owintotheboilerroom.VerifythetemperaturerangeonthethermalspillswitchisadequatefortheFlue
gas temperature from the SlimFit boiler. The use and set-point of this shall be determined by the system
designer.TheAutoresetinputontheBoiler’scontrolcanbeusedtowireinthethermalspillswitch.
The thermal spill switch should shut down all boilers connected to the common flue. Each boiler must be
wired to its own set of dry contacts activated by the spill switch.
 Increasingthenegativepressureintheventpipewillslightlyincreasetheringrateatlowre,thusreduc-
ingtheboiler’struemodulationrange.Considerthisfactorduringsystemdesign.
Code Compliance
Venting/Combustionairpiping–Installationsmustprovideprovisionsforcombustionand
ventilationairinaccordancewiththesection“VentingofEquipment”,oftheNationalFuelGasCode,
ANSIZ223.1/NFPA54,or“VentingSystemsandAirSupplyforappliances”oftheNaturalGasand
PropaneInstallationCode,CAN/CSAB149.1,orapplicableprovisionsofthelocalbuildingcodes.
TABLE 1 Rating & Vent Data
Boiler
Model
Input
Btuh
Stack / Vent
ow rate
scfm
Negative Pressure to be
maintained at
Vent Connection of the boiler
Inches w.c.
SlimFit Vent
Adapter
required for
Category II
SF 550 550,000 128 -0.001 to -0.100 6”- 8”
SF 750 750,000 175 -0.001 to -0.100 6”- 8”

SlimFit™Series 3 gas-fired water boiler — Application Guide
Part number SF-E009-A/0516 3
Thegurebelowrepresentsageneralcommonventingapproach.TheVentsystemforaCategoryIISlimFit
boiler is considered a Designed / Engineered vent system and should be designed by a professional using
accepted engineering practices.
Figure 1 Common vent

Part Number SF-E009-A/0516
Weil-McLain
500 Blaine Street
Michigan City, IN 46360-2388
http://www.weil-mclain.com
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SlimFit™Series 3 gas-fired water boiler — Application Guide