11
Part Number 550-110-737/1108
GWS-090E
Gas-Fired Water Boiler –
Boiler Manual
Figure 6
System bypass piping in boiler loop with
separate system circulator, using primary/
secondary piping
Figure 7
Boiler bypass piping — use only for high
water content systems — DO NOT use for
radiant panel systems
Near-boiler piping
continued
Install all components specified above and adjust valves as described to prevent low temperature in the boiler. Failure to
prevent low water temperature in the boiler could cause corrosion of the boiler sections or burners, resulting in severe
personal injury, death or substantial property damage.
3 Install water piping
continued
System bypass method
1. Apply bypass piping of Figure 6 to high water content systems,
radiant panel systems or any system that is likely to operate
with low return water temperature for extended periods.
2. The bypass arrangement shown protects the boiler from dam-
age caused by condensate corrosion due to low return water
temperature and protects low temperature systems from too
high a supply temperature.
3. Adjust the bypass valves as indicated below.
Adjust Bypass valves 1 and 2 as follows:
1. Start with valve 2 fully closed, valve 1 fully open.
2. Slowly open valve 2 while closing valve 1. Adjust the valves
until the boiler pressure/temperature gauge reads 160 °F or
higher. As you open the valves, pause long enough to allow
temperatures to level off. It takes a while for the boiler water
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. The purpose of this piping is to raise the return water tem-
perature to the boiler enough to prevent condensation of flue
gases.
Boiler bypass method
1. Apply bypass piping of Figure 7 to high water content systems,
such as converted gravity systems.
2. The bypass arrangement shown protects the boiler from dam-
age caused by condensate corrosion due to low return water
temperature. This method does not provide protection from
high temperature water being supplied to the system.
3. DO NOT apply this piping to radiant panel systems.
4. Adjust the bypass valves as indicated below.
Adjust Bypass valves 1 and 2 as follows:
1. Start with valve 1 fully closed, valve 2 fully open.
2. Slowly open valve 1 while closing valve 2. Adjust the valves
until the boiler pressure/temperature gauge reads approxi-
mately 60 °F higher than the system temperature gauge. As
you open the valves, pause long enough to allow temperatures
to level off. It takes a while for the boiler water temperature to
rise as the flow changes.
3. Bypass valve 1 controls system flow rate. Bypass valve 2
controls flow through the boiler.
4. The purpose of this piping is to cause a high enough tem-
perature rise in the boiler that the average temperature will
be warm enough to prevent condensation of flue gases.
