Boiler Temp.

hot_rod

with that 110- 115 number that many copper tube manufactures publish. I have replaced dozens of copper tube/ radiant boilers that corroded both flue and HX in short order when operated at that temperature for extended periods.

The boiler HX itself is only one part of the equasion. As important, and harder to diagonic is the conditions in the flue pipe from the boiler thru the roof.

Category 1 appliances need to assure that the flue by products remain in a vapor state to vent out. Should the temperature drop below dewpoint anywhere along the flue pipe travel, it turns to a liquid. This flue gas condensate will run a ph in the four to 5 range. This will very quickly disolve flue liners and any part of the HX the condensate collects.

Condensate corossion often leads to flue failure and potential flue gas leakage. Believe me I have seen B vent inner liners completly corrode away in a few years time from this!

This flue gas condensate also leads to the white lime or calicum deposits you may observe on the finned copper HX tubes.

If you chose to run those return temperatures for extended periods consider running some numbers with a combustion analyzer and a dewpoint chart, and keep an eye on the condition of that flue, especially with long runs and, or flue pipe runs in cold spaces, like ventilated attics!

hot rod

Mike Lundstrom

Boiler Temperatures

I was wondering if anybody can help me out here. I've seen articles saying not to run natural draft boilers (natural gas) at nothing less than 140F return temp. and then I just came across a copper tube boiler operating manual that stated no less than 110- 115. I am a little confused. I am putting a Burnham cast iron boiler in my house this fall and would like to use a outdoor reset so I really want to peg down the truth on this matter. I work for a school division with 16 schools and I am in charge of the heating systems. The boilers are all natural draft cast iron or copper tube or steel tube.

Thank You
Mike Lundstrom

Al Letellier

boiler temps

Mike, I would go with the manufacturer's recommendations for minimum return temps. It all has to do with boiler mass, flow and water content as to how much or at what point a boiler will condense or subject itself to thermal shock.

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