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Part Number 550-142-785/0812
4 Install water piping continued
GWI
Series 2 Gas-Fired Water Boilers – Boiler Manual
Figure 12 System bypass piping in boiler loop with
separate system circulator, using primary/
secondary piping
Figure 13 Boiler bypass piping — use only for high
water content systems — DO NOT use for
radiant panel systems
Near-boiler piping continued
Installallcomponentsspeciedaboveandadjustvalvesasdescribedtopreventlowtemperatureintheboiler.Failureto
preventlowwatertemperatureintheboilercouldcausecorrosionoftheboilersectionsorburners,resultinginsevere
personal injury, death or substantial property damage.
System bypass method
1. Apply bypass piping of Figure 12 to high water content
systems,radiantpanelsystemsoranysystemthatislikely
to operate with lowreturn water temperature forextended
periods.
2. Thebypassarrangementshownprotectstheboilerfromdam-
age caused by condensate corrosion due to low return water
temperatureandprotectslowtemperaturesystemsfromtoo
high a supply temperature.
3. Adjustthebypassvalvesasindicatedbelow.
Adjust Bypass valves 1 and 2 as follows:
1. Startwithvalve2fullyclosed,valve1fullyopen.
2. Slowlyopenvalve2whileclosingvalve1.Adjustthevalves
untiltheboilerpressure/temperaturegaugereads160°For
higher.Asyouopenthevalves,pauselongenoughtoallow
temperaturestoleveloff.Ittakesawhilefortheboilerwater
temperature to rise as the flow changes.
3. Bypass valve 2 allows hot boiler outlet water to blend with
colder return water, raising the supply temperature to the boiler.
Bypass valve 1 balances the pressure drop through valve 2.
4. Thepurposeofthispipingistoraisethereturnwatertem-
peraturetotheboilerenoughtopreventcondensationofue
gases.
Boiler bypass method
1. ApplybypasspipingofFigure 13 to high water content sys-
tems, such as converted gravity systems.
2. Thebypassarrangementshownprotectstheboilerfromdam-
age caused by condensate corrosion due to low return water
temperature.Thismethoddoesnotprovideprotectionfrom
high temperature water being supplied to the system.
3. DO NOT apply this piping to radiant panel systems.
4. Adjustthebypassvalvesasindicatedbelow.
Adjust Bypass valves 1 and 2 as follows:
1. Startwithvalve1fullyclosed,valve2fullyopen.
2. Slowlyopenvalve1whileclosingvalve2.Adjustthevalves
until the boiler pressure/temperature gauge reads approxi-
mately60°Fhigherthanthesystemtemperaturegauge.As
you open the valves, pause long enough to allow temperatures
toleveloff.Ittakesawhilefortheboilerwatertemperatureto
rise as the flow changes.
3. Bypass valve 1 controls system flow rate. Bypass valve 2
controls flow through the boiler.
4. The purposeofthispipingistocauseahighenough tem-
perature rise in the boiler that the average temperature will
bewarmenoughtopreventcondensationofuegases.
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