9
Part Number 550-110-832/1014
OWB & OWT
Series 2
Oil-Fired Water Boilers –
Boiler Manual
Near-boiler piping
continued
4 Connect 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
damage 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
temperature 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
damage 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 approximately
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
temperature rise in the boiler that the average temperature
will be warm enough to prevent condensation of flue gases.
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.
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.
