Navien question from new owner (Intelligent preheating with no external recirculation)

Discussion in 'Tankless Water Heater Forum' started by MacMan34, Jan 15, 2019.

  1. MacMan34

    MacMan34 New Member

    Jan 15, 2019
    Raleigh, NC
    Hey all,

    I am new to the world of tankless water heaters and am super excited by my new unit.

    Please forgive me if this is an obvious question or anything, I have been trying to search here and elsewhere since I decided to go with the Navien 240A.

    I see from the instructions that to turn on intelligent preheating you toggle the first 2 switches inside the control panel. From my reading this turns on both internal and external re-circulation.

    Is there any benefit to doing this without the external line? or does turning this on without the line possibly damage anything? I like the idea of there being readily available hot water in the internal re-circulation system when it believes demand will call for it (the wife gets up and showers at 5am, and I do about 6:30 five days a week), but am not at the moment at a place to install an external line or a Grundfos valve. Maybe one day....

    Any insight on this, along with any other advice you can give as I venture into the tankless water heater world, would be very much appreciated.

    Thanks so much and have a great day.

  2. SoCal Plumber

    SoCal Plumber New Member

    Feb 18, 2020

    There is NO benefit, there is a two way valve to turn inside the unit, as well, either INT or EXT. Set everything for Internal Pump and make sure your parameter settings are correct. Parameter setting P17 Enable Thermal Bypass, must turned ON. Both dip switches 1 and 2 are “on” but this is just setting for Intelligent Preheat for internal pumps. Individually switch’s 1 and 2 set INT or EXT pump settings but both on all that goes out the window. Best Advice, Properly service and maintenance your tankless! Figure how to do it on your own or call a plumber.

    Here’s a link to cop and paste for the install and operation guide.

    NPE_Installation_&_Operation_Manual_EN_CAFR_190529 ENGLISH.pdf
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