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Navien Heat Exchanger Failure

I am having issues with 2-Navien's. One is doing half of the domestic load only, the other is heating a basement slab with a heatbox & doing domestic for the other half of the house. The first units went out with bad heat exchangers after 6-mos. Now after replacing those first 2 in Feb of 2010, the second set is leaking again.

Both have recircs 210ANG,240ANG the  240ANG has a external pump because it is tied into a heat box & was installed as per Navien.

I had the water checked by a third party, and it came back well within the acceptable tolerances. Electrician checked for leakage of power or poor grounding, checked out good.

Now this is where it gets odd, the 1/2 proflo brass ball valve that isolates the recirc has developed a tiny pin-hole , healing itself as the deposit seals it up.

The Webstones feel a little crunchy.

 I thought I would do a little professional testing of my own on my finger and taste the mineral deposit to see if was salty or what. It was like licking a 9-volt, very bitter.

So, Navien jumped the gun & said it was the water, I said prove it. They have yet to tell me what  I need to look for in the water. This is a new issue for them? Basically, I need to know what the issue is before we move forward.

Any comment's or suggestions are welcome.


  • HDE_2
    HDE_2 Member Posts: 140
    What pump?

    Explain why the 240ANG would have an external pump when the pump in the heat box creates the flow through the Navien unit to make it fire?

    There should be no extra pump or circ between the heat box/Navien connections

    Did you add one (not shown in instructions) and by doing so double stack the units resulting in excessive head and flow?

  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    unscientific response

    but whenever I hear "pinhole leaks" and freshwater systems, I think electrolysis immediately.

    is it possible that you have a grounding issue?
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Jack
    Jack Member Posts: 1,047
    Did you check

    The waters ph. I recently was on a "problem" job, not navien, that had a water ph of 4. That is the ph of coca cola, or Pepsi even.
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