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Navien propane NR-240 shut down after 7 years

Hi folks,
Here is my issue. One day a few weeks ago, my tankless NR-240 shut down. Me being semi technical could tell the guy would not fire up..no ignition. I checked for codes and nothing. I had a "trained" Navien tech come out and make a long story short, after replacing the ignition, the PCB and then the gas valve the ubit will still not fire up. He checked the gas pressure and the readings were at first jumping all over the place to a constant drain. The prognosos was now not enough pressure from propane tank. Gas company comes over and says the piping is too small at 1/2" and should be 3/4" cause of the long run from one side of house to the other. Gas guy says " I think this unit was running hard these years and decided to burn out". The max load on unit id 199, 000 BTU and no way the pressure can get at 8-13 WC. I really dont get why I am not getting much of a pressure reading now when for 7 years it ran OK

thanks Paul


  • lchmb
    lchmb Member Posts: 2,997
    possible they set the pressure high to compensate. With that btu and style of unit you do need at least 3/4 for LPG. If you can do a diagram of existing piping in your house and btu load of all appliances (and length of run) it would be easy to size the system for you...
  • DZoro
    DZoro Member Posts: 1,048
    Boilers are like people when we are young we can overcome many obstacles, when we get old, not so much.
    I believe on that unit there is a air flow damper, on the exhaust side, I have seen those stick closed or slightly closed and cause the issue you are describing. If you have your tech contact Navien they can do a inducer blower rpm test, which may or may not confirm my suspicion. With the damper not fully functional will cause the unit to not fire, and yet have some gas flow but not the proper air gas mixture for fire.
  • GBart
    GBart Member Posts: 746
    why no fault codes?