As I am now dealing with a job that has Lochinvar CHHN0990 non-condensing boilers that were condensing in the boiler as well as the flue, I've done a little search and found that natural gas flue gas condenses at 60*C, which equals 140*F. Coincidentally, that is the minimum allowable return water temperature to these boilers. Return water less than 140* is no longer a problem.
As I have seen a lot of white crusty evidence of condensation on the flue where the flue goes thru an unconditioned/ventilated attic, would it be proper to assume the flue gas was/is dropping to 140* in this section? And to prove it, I want to test the flue gas temp at this point.
Does this make sense?
Anybody have experience with this?
BTW, both boilers, and the Lochinvar domestic boiler show the same condensation evidence.