Navien 240A suddenly not as hot in internal recirculating mode

Discussion in 'Tankless Water Heater Forum' started by mitch22, Apr 12, 2020.

  1. mitch22

    mitch22 New Member

    Joined:
    Apr 12, 2020
    Location:
    Washington
    Works fine with recirculation off, reaches the target temperature. But feels about 20 degrees cooler when I put it in internal recirculating mode. Confirmed the dip switches and valve position.

    This started a few weeks ago. Cleaned the water filters. Everything else seems to be in working order. Any ideas?
     
  2. HydroAirJoe

    HydroAirJoe New Member

    Joined:
    Feb 18, 2020
    Location:
    06820
    There is a check value in the T connection on the outlet of the pump. When this fails this will introduce cold water into the hot water stream. Depending on your cold water temperature you will get luke warm water to something like you described, 20 degrees cooler. On my NR-240A I had 2 of these fail in 2 years, and the most recent one was yesterday. Luckily I had a spare one since most parts distributions do not keep these in stock. The way to verify if the check valve is the issue, is to check the temperature of pipe coming out of the heat exchanager, if it feels hot, then the check valve is the issue. It easy to replace.
     
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  4. HydroAirJoe

    HydroAirJoe New Member

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    Feb 18, 2020
    Location:
    06820
    BTW, if this is a NR-240A, the part number is 30002282e
     
  5. mitch22

    mitch22 New Member

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    Apr 12, 2020
    Location:
    Washington
    Joe - that was the cause! Thanks so much!
     
  6. HydroAirJoe

    HydroAirJoe New Member

    Joined:
    Feb 18, 2020
    Location:
    06820
    Do you have a NPE or NR? On the NPE that check valve is much longer than the NR. It's weird that it took 8+ years before the first failure then I get another one 1+ year latter. There was was no debris in the old one, it just looked like the spring got weaker over time. Probably due to all the hand washing we are doing these days.

    I'm adding this part to the list of extras I keep so that I don't have to wait two-three days for a part to arrive. check valve, flame rod, flow sensor.
     
  7. mitch22

    mitch22 New Member

    Joined:
    Apr 12, 2020
    Location:
    Washington
    NPE. I've found the part online. On ours, the valve plunger had pushed through its closed / seated location. Re-assembling it worked, but am replacing it just in case.
     
  8. TxInjun

    TxInjun New Member

    Joined:
    Jan 20, 2020
    Location:
    San Jose CA
    Hello Mitch22,

    I too have a NPE-240A unit that is having a different / similar problem - in ext recirc mode, the water starts off hot and then the temp drops off in a couple of minutes. If I shut off and restart in a minute, the temp is back to scalding and slowly drops off again. I'm suspecting a leak in the check valve; also not sure if the temp sensor may need replacing and/or the water adjustment valve. I have ordered the replacement check valve - my question is: how easy / difficult is it to replace the check valve - do you unscrew it or does it just pop out with a pull on the black tab? And I assume the insertion of the new valve is just the same steps in reverse?

    Thanks for your assistance,

    Cheers

    TxIn
     
  9. mitch22

    mitch22 New Member

    Joined:
    Apr 12, 2020
    Location:
    Washington
    It's relatively easy. I think it was just a turn. It took more time to remove the assembly to reach it.
     
  10. TxInjun

    TxInjun New Member

    Joined:
    Jan 20, 2020
    Location:
    San Jose CA
    I want to thank HydroAir Joe and mitch22 - this thread solved my problem. It took me a few days to get the part in-house, but switching out the check valve was a breeze and now (just in time for summer, excellent timing wot) we have plenty'o hot water. The old check valve was indeed unable to fully close due to some mineral deposits on the sealing piston.

    Cheers,

    TxIn
     
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