Dew point on condensing boilers

[Johnyc86]

Can anyone tell me the dew points in kerosene and natural gas condensing boilers please.cant find answer online

 

[Chuck]

How accurately do you need the answer? From memory, for natural gas with 10% excess air (for maximum efficiency) the dew point is about 58°C, for oil it's about 49°C.

Don't forget that if you need a boiler to condense a useful fraction of the water vapour in the flue gas you need the return temperature to be significantly (say 5°C or more) lower than the theoretical dew-point.

 

[John.g]

 

[blockeddrainssydney]

Condensing Boilers Can Ensure a 90% Efficiency Rate
but Generally, conventional boilers can only reach 70-80% efficiency. These high-efficiency boilers owe a great deal of their heat conversion to their combustion chamber.

 

[John.g]

The big easily got gain with a HE boiler vs a SE boiler is the extra sensible heat extracted from the flue gases due to another Hx installed (called a economiser on steam boilers) which reduces the flue gases by ~ 150C leading to a 7% to 10% gain in efficiency, any condensing effect is a added bonus, fairly easily attained with outside temperature compensation.