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Boiler Exhaust Condensate

What causes the condensation in a boiler flue?


Back in the days of only Category 1 boiler and water heater flue systems, 17% of the heat produced by natural gas combustion when up the chimney.  This heat caused the "lift" of the flue gas and helped ensure that the poisonous gasses left the building.  The water vapor which formed during combustion would remain a vapor and would condense into water outside of the flue system.

But today's energy saving appliances heat our outside atmosphere a LOT less than they used to.  The heat is better utilized in our heating processes and this leads to energy savings.  With more heat entering the process there is less heat exiting out the boiler flue.  The water vapor formed during the combustion is less likely to remain a vapor.  As the temperature of the flue gas cools below "Dew Point", the water changes state to a liquid.

This liquid can easily absorb other products of combustion, like CO and CO2.  When this happens an acid is formed which is corrosive to many materials. 

Selkirk and HeatFab manufacture flue material from AL29-4C and Polypropylene which resist corrosion from the carbonic acid.  The acid can be routed to a neutralizer where a bed of magnesium hydroxide awaits it.  

JJM Boiler works published a white paper demonstrating why Mg[OH]2 is a far better product than limestone for your condensate neutralization.     

Heat Tech sales engineers love to talk about these concepts and we provide lunch and learn presentations on this topic as well as many others.  We welcome conversations about our quality products!


Product Spotlight:

Venting for boilers, fireplaces, grease duct, turbines, generators! Selkirk, inventors of the positive pressure system concept, exceed the requirements of codes and other manufacturers. Results of our testing programs illustrate this fact. We invite you to contact Heat Technology Products for details.