Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Single wall heat exchangers

BobZmuda Member Posts: 23
In 2015 Minnesota changed their code to allow single wall heat exchangers for DHW in boiler systems. There are some stipulations though such as a 30psi or lower relief valve on the boiler, the heat transfer medium should be potable water _or_ contain a fluid that has a toxicity class or rating of 1 according to some book published in 1984.

Apparently sentinel x100 meets this requirement BUT a local inspector is saying that no single wall heat exchangers can be used unless everything on the boiler side is rated for potable water. Pumps, 100 year old radiators, etc.

Also, you need some warning stickers.

IMO the UPC code is relying on the difference in pressure of the relief valves to prevent dangerous cross contamination. Because even if you meet the ridiculous standards of everything on the boiler side being rated for potable eventually the water you put in the boiler will become non potable after some time. I don't foresee anyone doing a daily flush of their boiler system to maintain potable water status.

Any thoughts? Help? lol. I'd like to be able to install combis or indirects if necessary.


  • DZoro
    DZoro Member Posts: 1,048
    overkill I'd say, you guys will live forever over there, government is taking good care of you :D
  • hot_rod
    hot_rod Member Posts: 22,271
    I'd check with the chief inspector, that doesn't sound like a viable option for any system.

    If the code changed to allow single wall it should be easier not harder?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Sticky wicket. Bottom line, the field AHJ has the final say so, regardless of what the code says. IAPMO does have an "Ask the Inspector" section on their web site, but I doubt you'd get anyone to pony up an opinion on this hot potato.

    I think a person has to say "Would I be comfortable drinking this water?" I think their biggest fear is not whats in the water now, but what HAS been (nitrates) in the water prior to this point in time. They used some seriously nasty chemicals, when and where they used chemicals.

    Double walled heat exchangers in and of themselves are not too bad at thermal transfer. It's when you throw the "Positive leak detection" into the mix that quashes thermal efficiency. That air gap kills it.


    There was an error rendering this rich post.