Navien NPE-240A2: No hot water in 1 shower

[younglloyd]

Hey! Thanks in advance for taking a look at my post if it is being discussed elsewhere please let me know.

My Navien NPE-240A2 has been working great for 2 years but over the last month has not been consistently providing hot water in 1 shower. There are no error codes. The other shower and all sinks in the house have no issue getting hot water.

I recently followed some YouTube videos and completed the annual maintenance and replaced the flow sensor but am still having the issue.

When the shower is lukewarm/cool the GPM on the Naiven is 0.5 but when it is hot the GPM is 1.3. Is there a way to make sure the GPM is always 1.3 when I use that shower?

To resolve the issue for now if the shower doesn't get hot I can turn on the sink in the bathroom and then the shower gets hot. Which we can live with but would ideally like for this to work properly.

 

[dgPlumb]

Same exact problem here on the same heater: it worked seamlessly for over a year and now, after a brief vacation, one shower cannot get hot water anymore and two sinks are flaky (some days they work, some days they don’t). I was planning to replace the flow sensor but after reading a few posts here I am not sure it will solve the problem anymore. I will let you know if I find a solution, please do the same, thank you

 

[Sponsor]

 

[GReynolds929]

Could be the check valve. @younglloyd if it's only happening at one shower I would replace the shower cartridge. There may be crossover happening.