Navien 240A Revving Noise

Discussion in 'Tankless Water Heater Forum' started by Richard Wick, Nov 29, 2019.

  1. Richard Wick

    Richard Wick New Member

    Nov 29, 2019
    Hello, hoping people here can help with a loud Navien 240A revving sound.

    Replaced two tanks that had a continuous circulation pump on dedicated copper recirculation line with a new Navien 240A tankless. Originally set to EXTERNAL recirculation using the pre-exisiting dedicated recirculation line and unfortunately, we had a water hammer effect in our walls. This only happened with the recirculation phase of the operation and was thought to be due to variation in pressure and temperature in the recirculation line.

    To remedy this, we worked with the plumber and navien sales rep to install a 6-gallan electric tank that supplies the dedicated recirculation line (DHW goes out from navien into the 6-gallon tank, hot water goes from the tank up to the house. Recirculation line comes back to the tank using a dedicated TACO pump). We now have it set to INTERNAL recirculation per the rep's recommendation (Switch in left lower portion of the unit set to INTERNAL, and dip switche set to 1-ON, 2-OFF, 3-OFF)

    About two weeks after this set up was done (not immediately after the extra tank install) we get a very loud noise from the inducer fan, AFTER the hot water is used and turned off (My understanding is this is at the time of the gas purge).Through trial and error, we have turned OFF recirculation completely (all DIP switches OFF) and we now get the loud "revving" sound when the unit kicks ON for a hot water pull from the house, but does NOT rev at the end(??).

    It is very loud and heard one floor up from where the unit is installed. I will try to post a video shortly (I think it's saying the file size is too large): This video was taken while it was still in the INTERNAL recirculation setup.

    Any help in understanding if this is a normal sound is appreciated. Honestly, it drives me nuts and I regret installing this Navien if this is thought to be a "normal" operational sound. Im wondering if its tied to the recirculation feature and/or a loose barring in the fan.
    Last edited: Nov 29, 2019
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    A tankless by itself probably does not call for an expansion tank, but when you add a tank to the mix, you probably do need one. If there isn't one, try adding one and see what happens. Heating water causes it to expand. The tankless system may have an internal check valve, so when the small water heater turns on to heat water, or hot water gets to it, you may end up with warmer water once you stop using it while the tank recovers. That expansion will raise the pressure, and potentially leak out somewhere. To see if that's the issue, pick up a water pressure gauge with a tattle tale second hand and leave it in place for a bit. The pressure should stay about the same. If it rises (maybe significantly) after hot water use stops, add an expansion tank.
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  4. Navien Inc

    Navien Inc New Member

    Sep 3, 2019
    20 Goodyear, Irvine, Ca
    For all issues with Navien units, we recommend that you call into our tech support at 1-800-519-8794 option 2 so that we can have our team diagnose the issue and provide a solution. Our tech support is available Mon-Fri from 8am - 9pm EST and Sat-Sun from 8am - 8pm EST.
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