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Radiant heat exchanger’s failure

RickF1963 Member Posts: 3
edited February 2023 in Radiant Heating
I have a zbr28-3a greenstar combination boiler that was installed in 2019 and the heat exchanger failed ( leaked) and was replaced on 10/5/21 under warranty and is now leaking again on the top left where the fitting (possibly stainless) is threaded or pressed into the aluminum heat exchanger, along with the seal on the front of the heat exchanger. There also is a leak on the impeller housing gasket where it is bolted to the motor. I’ve tried to contact the installer and he won’t return phone calls or texts. I have contacted the Bosch representative and he says that it’s likely due to me having “hot” natural gas being that I’m fed from a shallow gas well. Has anyone heard anything of this sort as I’m looking for suggestions on how to proceed since nobody wants to help. I’m currently waiting on a gas analysis to see if that’s possibly the culprit. When I looked in the back of my manual the installer failed to populate anything on the commissioning log such as CO2 and O2 readings. Any suggestions would be appreciated as I’m sure the Bosch representative is going to try to blame something other than a poorly over engineered unit!


  • HomerJSmith
    HomerJSmith Member Posts: 2,387
    You should have asked what he meant by "hot". I would think off hand that that would be gas that is more acidic, maybe with a lot of sulfur. Instead of calling go over there and face him, but don't be accusative. Act like you are working together to solve a problem.
  • RickF1963
    RickF1963 Member Posts: 3
    I have to attempt to get the Bosch representative out but want to get the gas analysis back first as that’s what he’s hanging his hat on with no proof. This my second boiler so 4 heat exchangers in 12 years, have to get to the bottom of it as it’s starting to sting!
  • Jamie Hall
    Jamie Hall Member Posts: 22,878
    That gas analysis is going to be interesting... if it shows a moderate amount of sulphur, or hydrogen sulphide, neither of which would surprise me at all, you've got a real problem. Both of those, as a result of combustion, turn into concentrated suphuric acid, which will do a number on any metal parts very quickly -- and it doesn't take much.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • kcopp
    kcopp Member Posts: 4,383
    You have a Shallow gas well? Is this Nat gas that is not connected to a utility? Please explain...
  • RickF1963
    RickF1963 Member Posts: 3
    Yes I have a gas well on my property that is tied into a bunch of wells in my area.
  • kcopp
    kcopp Member Posts: 4,383
    Not sure I buy the "hot" aspect but to Jaimes input there could be impurities in the gas. I have installed a few greenstar boilers. So far no issues.
    When I install anything and there are multiple failures in short period of time I have to think there is an outside influence.
    What if the water quality there? Especially with an all aluminum block that gets contact w/ the water you need to be careful.
  • hot_rod
    hot_rod Member Posts: 21,799
    They can fail from water quality inside out, also. If it is aluminum you need to watch ph of the water or fluid.

    Take a sample from a failed boiler before you flush and drain.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream