Navien NCB-240E Question

Discussion in 'Tankless Water Heater Forum' started by JRL84, Sep 28, 2020.

  1. JRL84

    JRL84 New Member

    Sep 28, 2020
    New York
    Hi Everyone,

    I just had my old Navien CH-210 replaced today with an NCB-240E.
    Here is my issue:

    When I turn on the heat, the unit kicks on and gets up to a range of temperature between 137-142. Within 10 minutes, it will drop below 135 and the unit will once again make the sound as if it is kicking back on. Is this normal or is there a setting I need to change.
    Thanks for the help.
    Last edited: Sep 28, 2020
  2. TEch99

    TEch99 New Member

    Oct 14, 2020
    Sounds like your running on a curve using temp readings from your outdoor sensor and since its still warm in NY it will do what you describe and stop around 140, when it gets colder it will reach the 150 or whatever yours is set to but it will pass the limits your currently seeing. Ensure your outdoor sensor is not laying around indoors.
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    FDNY/RETIRED New Member

    Sep 3, 2020
    Retired Lt FDNY/EMS
    TEch99 is right, but my first question is. Outdoor sensor is it hooked up? If it is do you see the O/R outdoor reset lit up blue? If you look at the User Info Manual page 7 where it shows what the icons are. If the light isn't on and you do not have a ODS it is running default mode with no Parameters set. That should give you min water temp 0f 104*F to 180*F max. Plus what is your return water temp? Press the mode button 3 times and INFO will show up. Look at the A: supply water temp, and B: supply return water temp. While it is running. Also if you look at G: that will also tell you if the Outdoor reset curve is on. A number between 1-7 means it is on.
    if it is -- -- -- it means it is off.

    Around Sept 28th where I live in NY the night time temp only 68*F. Today right now 39*F according to my info for my ODS. So one way or another if your unit is running. I do not think you should be cycling, with the gas light going on and off. That's if you have your thermostat set to stay on. You should hear it modulating and I believe the gas light should be staying on. That is what mine is doing right now and I took my Nest E taken off Eco which I have set at 65*, and I set it at 71*F. Don't know what type thermostat you have. Also how many zones do you have? If I am wrong about the gas light staying on. Please someone correct me. Because I am just a homeowner and getting use to how my unit is operating. Let alone the Nest Thermostat.
    Right now A: 160*F B: between 140 to 149*F, I am set to G:1 for finned tube baseboard. Everything else is set to defaults, except my F: Max Heat capacity for space heating which is at 80%. I think I am still to high on my return water for proper condensing.
    Last edited: Nov 16, 2020
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