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Advice requested: Navien tankless heater releasing more gas than it should through the vent


I had posed this question on Reddit originally and someone suggested posting here, so I am just going to copy past the issue.

New to home ownership and this bit of trouble arose today. I have the Navien NCB-180E heater in the basement that heats my condo and the water. I had been smelling gas coming out of it's vent, which is outside of the house, ever since I moved in 4 months ago. But I always assumed that it might just be residue. However, my neighbor's plumber smelled the gas today and did not like how strong it was so he asked me to shut it off and call the gas company. I did exactly that and someone from the gas company showed up. They scanned the vent and concluded that it was releasing too much gas so they shut the heater off and asked me to get it fixed. They didn't share what the reading was and I wasn't smart enough to ask.

I called the manufacturer and they downplayed the situation stating that the gas companies tend to exaggerate things and that as long as the gas is coming only out of the vent and not the actual heater which is located within the basement (gas is indeed not leaked/released in the basement). I have a 3 month old so I had to be extra careful and therefore chose to side with what the gas company concluded and have left the heater shut. I then called many plumbers because apparently this type of unit is still relatively new in the market so not many people out there know how to troubleshoot it. One plumber returned my call and pretty much echoed what the manufacturer was saying.

What would you guys do in my situation? Perhaps have a plumber come in and perform scan the vent and call back the manufacturer? One responder on Reddit suggested having the plumber perform some sort of combustion analysis to see whether I have an incomplete combustion situation going on. Is that a good start? Anything else? We basically have no heat and hot water now and it is supposed to be <60 degrees the next few days, so appreciate any advice.


    HVACNUT Member Posts: 5,763
    I cant see any manufacturers Rep, yes even Navien, tell you excessive gas fumes from the exhaust vent is normal and downplay a potentially dangerous situation.
    Their Tech Support discussed issues with you knowing your not a Tech? I dont see that happening either.

    Do not call just a plumber. You need a qualified heating Tech to troubleshoot, set up, and perform a combustion analysis.

    Do not turn the boiler on until it's been serviced by a pro.
  • lchmb
    lchmb Member Posts: 2,997
    a test of the vent proves nothing. A pressure test to the unit in question to see if it is leaking by and combustion test to start would be minimum. Safety first..find a gas tech..
  • Zman
    Zman Member Posts: 7,553
    I would say you either you have a bad gas valve or very poor combustion.
    Find a qualified tech with a combustion analyzer.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein