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Crown Phantom 80 Heat Exchanger Corrosion

DinoRoberti Member Posts: 9
edited November 2021 in Gas Heating
Inspection of a Crown Phantom 80 heat exchanger was performed after 1 year of service after installation. I was shocked to see this much corrosion activity in one year of operation. The boiler uses natural gas and setup with an outdoor reset programmed with 120-160 degrees operating temperature. The boiler supply is pumped into the bottom of the buffer tank and return off of the top of the tank to minimize condensing to extend heat exchanger life. The buffer tanks supplies panel radiators with TRVs and radiant floor zones. With return temperatures into the boiler above 127 degrees for a majority of the heating season, this boiler primarily operates in a non condensing mode with 87% efficiency. Is this normal to have this much corrosion in one year operation? How will the boiler lockout as the corrosion worsens. At this rate of corrosion how long until the heat exchanger have to be replaced? image

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    EBEBRATT-Ed Member Posts: 13,422
    If it's a non condensing boiler you need to get the temperature up over 130. This looks like it's running with a low temperature too much.

    There are many things that "might" work.

    In my opinion a three way valve with a sensor on the boiler return line is the only fix
  • hot_rod
    hot_rod Member Posts: 19,260
    was the burner dialed in with a combustion analyzer?
    is the intake air near the exhaust, recirculating exhaust gas?
    does it get clean air, no dirt or gravel roads, tree pollen?

    They are what they breathe
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • DinoRoberti
    DinoRoberti Member Posts: 9
    Yes, a combustion analyzer was used to tune the boiler. A concentric vent is used and it does not recycle the exhaust. The vent gets clean outside air.
  • clammy
    clammy Member Posts: 2,910
    That boiler is a condensing modulating boiler reverse piping of the buffer tank defeats the purpose . This boiler is designed to condense by piping the buffer in reverse u end up w a elevated return temp totally defeating the purpose . If piped correctly the buffer tank would have some temperature stratafaction which I would guess is not occurring . I ve done the same thing piped correctly and ended up w long burner run cycles and zero short cycling and a decent temp diff between both boiler supply and return and system s and r and also using panel rads and constant circ on the system side ,I would lose tank stratafaction only when system pumps where running w no boiler pump running found larger to across boiler then system so I removed the system sensor and just ran boiler off t stat and system pump off a simple ranco etc and it’s work perfect for close to 10 years . That staining may be from prolong low fire and or from running in a non condensing mode . I would clean the heat exchanger and re test the combustion and also chk your temps when in heating mode and producing portable water . I ve seen worse . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
    EBEBRATT-Ed Member Posts: 13,422

    That boiler has been discontinued. Too bad. Another strike against MOD CONS IMHO. Who wants to put their confidence in a boiler line that is no longer made and maybe you can't get parts for??

    I don't know if your hooked up primary secondary but Crown strongly recommends that for that boiler
  • kcopp
    kcopp Member Posts: 4,187
    I would not classify that as corrosion.
    For that style of boiler (water tube) that looks like pretty normal residue for the combustion process. Im guessing its LP gas. Clean it up w a scotch brite pad and some white vinegar and flush.