Hello all. I was hoping to get some help here. This evening my daughter came in saying there was no water coming out of the hot water faucet in her bathroom. Upon inspection, I realized that the water from the hot side had completely stopped flowing from all of our faucets and showers in the entire house. (the cold side of the faucets is flowing just fine)
We have a Navien 180A tankless gas water heater.
I discovered that, when I powered off the water heater, the hot side of the faucets started flowing again (cold water of course). But as soon as I power the heater back on, it shuts off the water on the hot side of all the faucets in the house.
I don't know anything about tankless water heaters so I was hoping someone here could give me some advice.
The crazy (frustrating) thing is... We actually sold this house! We literally closed escrow last week and we're renting it back for a few weeks before we move. Ugh.
Thanks in advance!
I've had the same thing occur a couple of weeks ago with our 240A unit installed in our new house about 6 years ago. The unit has been fantastic few issues the entire time. My unit has internal circ and no external circ loop; all Pex piping and direct runs to points of use from a manifold adjacent to the heater and cold water sources. My filters were all clean and I had done a flush 6 months ago. For testing, I used a garden hose right at the valves from hot water from the heater to easily test on/off and "adjust" test flows. Fully open, and zero flow as you indicated. After calling Tech support and insisting on a level 2 technician, he walked me through questions and directed me to make one change. On the front panel dip switches behind the rubber cover, he directed me to move DIP 6 to UP. Bingo, water flowing again and heated properly. He insisted that flush cleaning is key and a flow problem due to being unclean could be the issue. Strange. So I set about getting the vinegar and ran the system normally for a few days until I could get this done. I did the 45 minute flush per the manual procedure. Reset DIP 6 Down since it had been that way since installation. No hot water!!
Frustrated, I put 6 back up and started searching until I could fine the Operation AND Installation manual, the latter naturally never left on site as is often the case at install. I am a retired HVAC controls engineer and not going to rest until it all worked and I understood why things did what they did.
In the process, I realized (a) my internal recirc pump was never running (DIP 1 should have been up at install and was not) Set it to on and noted lighted symbol now on the display shows but only of DIP 6 is down/off. (b) cold supply water was not getting through the servo controlled water distribution valve so I needed to figure out why. In the beginning I had not tried fully power down the unit and see if water did flow through this however (it should). (c) the 'info" button cycled to GPM display shows flow not only when a hot faucet opens/adjusts but ALSO when there is internal recirc. More on this later.
I theorized that the valve was stuck or not being turned/sensed rotated by the system computer and decided (maybe a bad idea) to take off the plastic control servo unit fron that water way valve. Doing so, I could see 0-315 deg rotation markings on the parts and I marked positions, unpowered, of each rotating part. With cold supply off, I tried manually rotating the valve a bit CW (opening) and CCW close. It seemed stiff so I worked it back and forth a dozen times. Then re-attached the servo motor, turned on water and power. NO JOY.
So I decided tp reset the starting position of the valves shaft to be further open "at rest" somewhere at what read as 0.4 gpm. THen cycled power to watch the motor movement detached from that valve stem. It seemed on power up, it tries to rotate a few degrees open then recloses but I hear what sounds like a clutch knocking several times when it moves to the stop at closing. Humm, perhaps something wrong? (Later on after talking with Tech support again, he told me taking that off likely ruined the valve/actuator or it could have been defective and there is no way to recalibrate it which I questioned providing it responds and rotates on command from the computer board which it did) I have a new one on order just in case now.
However, through this process I DID GET hot water flowing and tested normal operation now with DIP 1 ON and DIP 6 back to OFF. I can hear the internal circ pump work, burner modulate on/off, internal tank warm up, etc. Other than the clicking sounds a few times when the system is fully on, and cooling post purge ends, it continued to operate fine for a couple of days now. I will add to this diatribe later when I get the new servo valve and go from there.
Hopes this helps. Do not try this at home. Your mileage may vary. I'm convinced our installer (who my builder picked) was not properly trained on what to set initially and will look for a local properly certified contractor so I don't need to dig into this myself in the future.