NBE RTB Owner's Manual - page 26
Flue gas condensation:
When a boiler has an extremely high efficiency> 93%, the temperature of the flue gas is naturally
low. Typical flue loss is only 2-3%. This creates greater demands on your chimney and on how to
adapt the boiler to its existing installations. It is important, if you have condensation to prevent it;
otherwise you risk developing soot into the chimney and corrosion on the boiler.
Note:
that even if there is water in the boiler it may come from the chimney.
Things that can prevent condensation in the boiler and chimney.
1. High chimney> 5m.
Provides a good draft in all conditions.
2. Small clearing in the chimney 125mm-150mm.
Provides better flow, and can "carry“ out more moisture.
3. Short un-insulated smoke pipe
Do not cool down the smoke unnecessarily before it
reaches the chimney.
4. Draft stabilizer.
Stabilizes the draft, and provides the chimney with dry air.
5. High boiler temperature> 70C degrees.
10 degrees up in the boiler temperature gives 10 degrees more smoke temperature.
6. Suitable return temperature> 55C degrees.
Hits the smoke boiler surfaces under 47C degrees, it starts condensing.
7. Open bypass in the boiler (applicable only on BS1016, BS2030, BS4050).
Release the smoke before the last smoke cooler,
15C degrees increase in temperature of the smoke,
only costs approx. 1% in efficiency.
8. Heated boiler room.
Lowers cooling of the boiler and smoke pipe
and provides draft stabilizer more hot air to work with.
9. More oxygen in combustion.
Increases air flow in the boiler, and carries more moisture,
1% more oxygen costs approx. 0.5% in efficiency.
10. Remove the Turbulators
Decreases resistance of the boiler,
and get a bad chimney to work better
The gas temperature typically increases
to approx. 100 degrees.
The burner should be readjusted
after the turbulators are removed.
11. Extend the heating cycle when only running DHW priority
During the summertime, it is common to use the DHW priority feature in the controller.
If you are noticing condensation in the boiler, a strategy to prevent condensation is to
extend the heating cycle by slowing the regulation(PI settings) so as to allow for
greater time for the boiler to dry out.
12. Mount exhaust fan to chimney.
Helps the flow the right way, from CHIP 6.82
can exhaust fan be connected directly to the controller.