Navien NPE-240A condensate drain leak

[BabaCharles]

I bought a home a few months ago that had a Navien tankless water heater installed in 2019. Yesterday I noticed lots of water coming out of the condensate drain. The floor beneath the unit was a little wet too but whatever caused that bit of moisture has seemed to have stopped. But the water flowing out the condensate drain is continuous. It only stops if I shut off the water valve. Called plumber over to take a look. They said they’ve never seen this problem before. They called Navien and unfortunately my serial number was never registered so I’m told it isn’t under warranty. They are giving me the options to troubleshoot the unit for possibly $700 or more or to install a new one for about $5000. I figured at this point I’d try and troubleshoot it myself. I don’t know where to start though. We have had another plumbing issue with a leaky tub faucet. Seems like the water here is very hard. Any guidance would be appreciated. Thank you.

 

[Breplum]

First off, Navien tech will provide support, even out of warranty. Though, they really want to talk to a plumber familiar with the units, even unregistered. They understandably have to hesitate, when, if un registered, have chance that installer did not follow guidelines.
And, replacing: New updated model cost us about $1,600 plus tax. And they swap out easily in most situations. (two people needed just because it is heavy).
Send pics and I can respond more accurately.
Water flowing out the condensate is very very, weird. Condensate flows from the sealed heat exchanger and might be that it has failed. Failure would be extremely rare because it is pure stainless steel.
Can you get purchase receipt from the sellers? The receipt would have the serial number on it typically.
Heat exchanger is a pain to replace (covered under normal warranty), so in your case, would not want to pay labor to do the exchanger if part is not covered.
You could fly me down on JetSuiteX and limo me over for the few hours and it wouldn't cost $5K.

 

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[Fitter30]

It is a possibility that the heat exchanger is compromised and the leak cold be leaking burner side running out the conensate. Burner condensate runs 2-4 ph litmus paper to test it. Distilled water 7. Test boiler water just for a baseline. I've seen heat exchangers only leak under fire. More.likely on the dhw side.

 

[Allanlo]

I had the same issue. The O-ring between the flow sensor on the inlet was bad. Replaced it and the problem was resolved. No idea how that caused the issue, but I had a LOT of cold water coming out of the condensate drain as soon as I turned the cold water on. Boiler was unplugged at the time. Hope that helps someone.