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flue gases with old CI rads on conventional gas boiler

kensheets2 Member Posts: 36
edited January 2021 in Plumbing
I understand that with low water temp installations such as radiant floor heating, return water temps will naturally be less than ideal. My question is if I am running an application using old cast iron rads with a conventional gas boiler and running water around 170-180 will I realistically still need to be concerned with low return water temps in relation to flue gas condensation?



  • Jamie Hall
    Jamie Hall Member Posts: 23,305
    Probably not. The concern arises when the return water to the boiler drops below about 140 -- and stays there -- while the boiler is running. Mostly a control issue. Make sure the boiler is set to hold a source temperature high enough, and to make sure there is enough circulation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England