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Issue with Navien flow sensor

zepfan
zepfan Member Posts: 412
in Domestic Hot Water

About five years ago we installed 12 Navien tankless gas water heaters model # NPE-240a. These were installed in several houses in the same neighborhood, on the same city water service. One of the units has had the flow sensor fail, three times within the last five years, since the unit was installed. the other 11 have operated without one issue. I have spoke with Navien and they don't seem to have a solution. Has anyone every heard of this or ran into the same issue? My first thoughts were higher then normal water pressure, but the pressure seems to be the same on the entire street, around 60 psi. Any ideas as to what could be causing these sensors to fail would be much appreciated. Thanks to all.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,777

    Maybe put in a PRV to lower the pressure to 40psi maybe water hammer is causing it? Just a wild guess.

    zepfan
  • hot_rod
    hot_rod Member Posts: 23,762

    put a gauge like this on the system for a few days or a week. It will catch a spike from water hammer or a failed regulator

    IMG_9141.jpeg

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GGross
    GGross Member Posts: 1,357

    Have you run the high pressure idea past navien tech support? according to their documents the unit is rated for 15-150PSI. is there an inlet filter on the unit? what do the failed flow sensors look like when you pull them out? what is the nature of the failure, electrical physical damage etc. multiple failures of the same part on the same install usually implies something else is at play imo. need more info

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