Navien NR-210 set at 113F goingextremely hot to cold and back again to normal

Slippers

Hi just a few questions if I may. I had the unit installed now for about 6-7 years. My problem is this. About a week ago I noticed that I was taking a shower and the water got extremely hot then it went cold ( like I ran out of propane) then it came back to normal maybe a little hotter. I recently cleaned the unit for the 1st time didn't know I had to do anything other than clean the dirt trap (i ran 3 gallons of white vinegar through it for about 4 hours). Doing research on it I changed the flow sensor cleaned the cold water filter ( is there on on the hot outflow?) and the air intake screen. It's still doing it. What could it be? Maybe the mixing valve or the actual temperature sensors. I have never had a code during any of this and the only time I ever do get a code is when I run out of propane and need to f

Change the tank ( have it hooked up to 100 Lb tank about 23 gallon at a time ) any ideas on what it could be . The plumber who installed it is retired and moved out of state and I'm a DIY as much as possible. One other question is they put a regulator out where I connect the tank going fron 1/4 copper line to the 1/2 in regulator to the 3/4 Black pipe to the unit. My question is does the unit have it's own gas regulator built in or does it need the one outside. The unit has been running trouble free all this time thanks to God ( not knowing about the yearly cleaning being needed LoL. Any help on what part is obviously going bad would be greatly appreciated thank ahead of time-----Richard

GroundUp

Is there an external mixing valve in the piping? No, there is no internal regulator and you need one inline. This isn't really a DIY project- the flame side also needs to be cleaned and the combustion needs to be analyzed and tuned

Slippers

No there's an internal mixing valve in the unit. All parts are modular,( just pull a stainless steel clip on both sides of said part and replace with new part. As far as the flame side I have watched it running while another family member is showing and nothing changes it's pretty much rock solid when it's running just the cold water sandwich issue. Do you think it could be the mixing valve . Do the temperature sensors on hot side go bad ? Thank you for replying

psb75

The mixing valve is a mechanical device that can go bad. When it fails it fails to "cold." Temp. sensors also can go bad. Try talking to Navien tech support.

Slippers

Yes been trying to get ahold of them haven't had much luck with a call back yet. Still trying to troubleshoot what it could be in the meantime. Anyone what would cause the nr210 to turn on normal set at 113F for 5-6 minutes then get pretty hot almost scalding then  completely drop out to cold water then gradually come back to hot and stay there( all without setting a code . Like I said before I cleaned the unit performed standard maintenance and changed the flow sensor. Other than that it's all original OEM. And for **** and giggles could it be the regulator at the tank failing /starting to it is original from install 2012/2013.  

GroundUp

Watching the flame doesn't tune the burner. This is not a DIY thing.

Slippers

Hey I'm not saying I'm doing anything regarding the flame DIY I'm only asking people that have delt with these units for some insight into what it could be. I'm in CT and throwing parts at it is almost to only option at the moment. Getting someone to come that has ANY idea about the unit (besides telling me that there a pice of **** and they don't service them) and the rest of this God forsaken state staying home and making more on unemployment. Besides I'm a licensed electrician and and mechanical engineer to boot. Hell I service fuel systems on Blackhawks for a living dealing with a damn hot water heater isn't an issue. All I'm asking for is the experience of others who may have come across this issue and have an idea on what's wrong. On a side note I did an experiment this morning  the temp started to drop off and I jumped out of the shower and turned on the hot side of the sink low and behold the temperature came back to normal and stayed there ( was reading a post someplace and that was a suggestion to try but I can't find the thread to see what the fix was). It seems like it's a flow issue but I already replaced the flow sensor in less there's another Method the unit uses to determine water flow besides the flow sensor. ADVICE welcome CRITICISM is not.

psb75

You probably should take the shower head off and see if it has some mineralized 'crud' in it. Often its created by the on-demand hot water unit and it can plug shower heads, faucet aerators, and washing machine hot water inlets. That has worked for me in the past.

psb75

Hey, I just read about some "recently-broken" Blackhawks in the news! Hopefully you don't have a broken Navien, and it may just be something simple. We're humble mechanics ourselves on this forum and are frequently surprised at how simple "the fix" often is.

Slippers

I'll try the suggestion ty . Yes we're still trying to figure out what happened in San Diego and as far as the 108 BH over in Afghanistan who knows why there not working anymore 😉