7Part Number 550-110-832/1014
OWB & OWT
Series 2 Oil-Fired Water Boilers – Boiler Manual
4 Connect water piping
Expansion tank
Diaphragm- or bladder-type expansion tank — Figure 3,
page 8
1. Ensure expansion tank size will handle boiler and system
water volume and temperature.Tank must be located in boiler
returnpipingasclosetoboileraspossible,beforeinletside
ofcirculator.Seetankmanufacturer’sinstructionsfordetails.
2. Installanautomaticairventasshown.
Closed-type expansion tank — Figure 4, page 8
1. Ensureexpansiontanksizewillhandleboilerandsystemwater
volumeandtemperature.Seetankmanufacturer’sinstructions
fordetails.
2. Connecttankto½”NPTtappinglocatedbehindsupplyoutlet,
using½”NPTpiping.Pitchanyhorizontalpipinguptowards
tank1inchper5feetofpiping.
Undersizedexpansiontanks cause system water
tobelostfromreliefvalveandmakeupwatertobe
addedthroughllvalve.Eventualsectionfailurecan
result.
General
If installation is to comply with ASME an additional high
temperaturelimitisneeded.Installcontrolinsupplypipingbetween
boiler and isolation valve. Set second control to minimum 20 °F
abovesetpointofrstcontrol.Maximumallowablesetpointis240
°F.Seepage13forwiring.
Alowwatercutoffdeviceisrequiredwhenboilerisinstalledabove
radiation level or by certain state or local codes or insurance
companies.Uselowwatercutoffdesignedforwaterinstallations.
Electrodeprobe-typeisrecommended. Purchaseandinstallin
tee in supply piping above boiler.
Usebackowcheckvalveincoldwatersupplyifrequiredbylocal
codes.
Water piping — multiple zone systems
Installsystempipingusingeithercirculatorzoningorzonevalve
zoning.Installexpansiontankonsuctionsideofsystempump.
Always connect fill line only at the expansion tank — never at
another point in the system.
Relief valve
Installreliefvalveverticallyin¾”tappingonrearofboilerusing¾”
nipple and elbow supplied in bag with valve. See the tag attached
tothereliefvalveformanufacturer’sinstructions.
To avoid water damage or scalding due to valve
operation, discharge line must be connected to
reliefvalveoutletandruntoasafeplaceofdisposal.
Terminate the discharge line to eliminate possibility
ofsevereburnsshouldthevalvedischarge.
• Dischargelinemustbeasshortaspossibleandbe
the same size as the valve discharge connection
throughout its entire length.
• Dischargelinemustpitchdownwardfromthevalve
and terminate at least 6” above the floor drain where
any discharge will be clearly visible.
• Thedischargelineshallterminateplain,notthreaded,
with a material serviceable for temperatures of
375 °F or greater.
• Do not pipe the discharge to any place where
freezingcouldoccur.
• Noshutoffvalveshallbeinstalledbetweentherelief
valve and boiler, or in the discharge line. Do not plug
or place any obstruction in the discharge line.
• Failuretocomplywiththeaboveguidelinescould
resultinfailureofthereliefvalvetooperate,resulting
in possibility of severe personal injury, death or
substantial property damage.
• Test the operation of the valve after lling and
pressurizingsystembyliftingthelever.Makesure
the valve discharges freely. If the valve fails to
operatecorrectly,replaceitwithanewreliefvalve.
Circulator
The circulator is shipped loose (wiring pre-attached to boiler)
to allow you to locate it either in the return or supply piping, as
desired.Seepage8foratypicalinstallation.Pipetheexpansion
tanktothesuctionsideofthecirculatorwheneverpossible.Install
an air separator in the supply piping. Connect the expansion tank
totheairseparatoronlyiftheseparatorisonthesuctionsideof
the circulator. Always install the system fill connection at the same
point as the expansion tank connection to the system. Figures 3
and 4, on page 8, show typical near-boiler piping connections.
Near-boiler piping continued
SeeFigure3(diaphragm-typeorbladder-typeexpansiontank)
orFigure4(closed-typeexpansiontank)onpage8,andTable
4, for near-boiler and single-zone systems designed for return
wateratleast130°F.SeeFigure6or7,page9forlowreturn
temperature applications.
Seethispageformultiple-zonepiping.
Seepage8forboilersusedwithrefrigerationsystems.
Near-boiler piping
Boiler
model
number
To
system
From
system
OWB/OWT-3 1-1/4” 1-1/4”
OWB/OWT-4 1-1/4” 1-1/4”
OWB/OWT-5 1-1/2” 1-1/2”
OWB/OWT-6 1-1/2” 1-1/2”
All piping sizes based on 20° F temperature rise through boiler.
Table 4 Water pipe size (based on 20 °F rise)
Boiler
model
number
To
system
From
system
OWB/OWT-3 1-1/4” 1-1/4”
OWB/OWT-4 1-1/4” 1-1/4”
OWB/OWT-5 1-1/2” 1-1/2”
OWB/OWT-6 1-1/2” 1-1/2”
All piping sizes based on 20° F temperature rise through boiler.
