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Thread: Navien LP to NG conversion - not possible?

  1. #1
    DIY Junior Member kwadz's Avatar
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    Default Navien LP to NG conversion - not possible?

    Ok, so when I bought my house, I knew I'd be converting to NG within a few years. Our old tank wh was leaking so we replaced it with a Navien NR-240A (LP model) tankless. Our plumber told us that Navien's rep directly told him it was convertible to NG (and we unfortunately did not get this in writing). Well, we now have NG in the house and when we contacted Navien to see if they had a conversion kit, they told us the unit is NOT convertible and that we would have to buy a brand new unit...and our "old" one is only 2 years old!

    I know, shame on us for not verifying everything and trusting our plumber. Our plumber insists, however, that #1 - Navien originally told him it was convertible and #2 - even though they now say it isn't, he can and will convert it for us by just changing the orifice.

    I need to understand from those of you "in the know" what will or may happen if he "converts" it by just changing the orifice to allow more NG into the unit (to make up for its difference from LP). Will the unit catch fire, blow up, destroy our house, annihilate our county? Or will it just stop working? Or will nothing happen and it may continue to run for years without any problems?

    At this point, unless there's a safety issue involved, we're at a loss anyway so I see no harm in just letting him convert it the way he thinks it will work. Any input? Don't worry - I'm not a lawyer and I won't legally hold anyone to his opinion on here if anything does happen. My wife is just worried and wants to know what we're facing. Thanks in advance!

  2. #2
    In the trades Dana's Avatar
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    Letting some random guy install a manufacturer-discouraged hack onto the unit may indeed have serious safety consequences. Before you let him do it make sure he is a licensed-bonded contractor with a combustion analyzer (and knows how to use it), and is willing to sign up for the liability for any modifications made.

    If he screws it up the risks of it blowing up or burning your house down are probably lower than those of improper combustion and major soot issues, along with extreme levels of carbon monoxide in the exhaust. Those things would show up in the combustion analysis.

    Curiously, Navien sells kits for making those conversions on the NPE series, but explicitly states in the manuals for the NR series that it can't be field converted. See the warning on the bottom of p.13. Since it may require a software change in the control electronics or something, simply monkeying with the mixtures probably isn't a good idea.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    If it were possible, it would require both a regulator change and orifice changes, and then recalibrating the fuel mixture. I do not think you could do any propane to NG conversion otherwise. The logic to regulate the flame to the water use may be affected, which could throw the whole thing off as well. Performing modifications not approved by the manufacturer voids any warranty and certification on the unit, potentially also affecting your insurance should you have an accident caused by those changes...IOW, not good...do not tweak gas appliances and lose the certifications!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    DIY Junior Member Jymer's Avatar
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    Only the new models are convertible. They send the kit in the new models as well. I have the NR 210A and it's not possible to do it safely. Don't play with it.

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