No water flow - tankless water heater (Navien)

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davidcom

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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!
 

WorthFlorida

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I know nothing about these models but the number one fault problem learned over the years from this forum, it is the air intake. There is a filter screen that clogs up preventing enough combustible air to enter. If I recall it's causes warm water or cold but not completely shut off. It is something to check.

https://www.navieninc.com/products/npe-180a

Unplug the unit before doing any work on it.

navien-filter-2.jpg
 
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davidcom

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Hey thanks @WorthFlorida. I took a look at the diagram link you shared. I see the PVC air intake venting at the top left. But I don't see any mention of a filter screen. Any idea where that is located?

Also, you mentioned "If I recall it's causes warm water or cold but not completely shut off." In my case, the hot water flow is completely shut off. Not even a trickle comes out.

Thanks again!
 

davidcom

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@WorthFlorida I found the user manual through the link you sent me and have located the air intake filter and the water inlet filter. I'm going to try to clean both of those. I'll report back!
 

Reach4

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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.
This made me wonder who is responsible for repairs during this period. https://www.ncrealtors.org/wp-content/uploads/markup0718-2A8-T.pdf is a model/form rent-back agreement, and it says
Seller shall be responsible for the maintenance and repair of all appliances, systems and equipment on the Property other than any appliances, systems and equipment described above.​

You knew this I expect, but I didn't, and now I do.
 

davidcom

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This made me wonder who is responsible for repairs during this period. https://www.ncrealtors.org/wp-content/uploads/markup0718-2A8-T.pdf is a model/form rent-back agreement, and it says
Seller shall be responsible for the maintenance and repair of all appliances, systems and equipment on the Property other than any appliances, systems and equipment described above.​

You knew this I expect, but I didn't, and now I do.

Yeah, it's an interesting situation. The buyer just closed last week. He's giving us free rentback for 30 days, as we prepare for our move. Even if the new buyer were responsible for repairs, I'd feel really bad saying "Hey, you're not going to believe this, but just a few days after you bought our house, the water heater went out. As you're now the landlord giving us free rent, you need to pay for the repair! :D
 

Reach4

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Hey thanks @WorthFlorida. I took a look at the diagram link you shared. I see the PVC air intake venting at the top left. But I don't see any mention of a filter screen. Any idea where that is located?
https://www.navieninc.com/downloads/npe-user-s-information-manual-en

Page 13 upper right shows that filter in the generic manual.

See the maintenance section in chapter 4 for other stuff to do.

https://www.navieninc.com/products/npe-180a is specific to 180A

Would you put a tankless into your next house if the existing WH failed and enough gas was available?
 

davidcom

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Thanks to all. I got it working. For anyone else in the future, here's what I did:
  1. Followed the instructions in the manual for draining the water heater.
  2. Removed and cleaned the air intake filter - this wasn't very dirty. Just had a couple of bugs in it.
  3. Removed and cleaned the Recirculation Inlet Filter - This wasn't really dirty at all.
  4. Removed and cleaned the Cold Water Inlet Filter - This didn't look terrible, but it did have some calcium buildup. I cleaned all that out.
  5. Removed and cleaned the "Condensate Water Clean-Out" (basically a dirt trap)
  6. Put everything back together.
I didn't have high hopes that the various filter cleanings would fix the issue, because none of them were very dirty. But when I put it all back together and turned it on, the hot water started flowing again and it was heated. Success!

Thanks again!

@Reach4 yes, I think I would install it into my next house. I've got 2 teenage girls and it's nice that we never have to worry about the hot water going out! :)
 

Jeff H Young

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davidcom, just wondering because I don't work with tankless that much how long have you had one? and did you ever flush the system out with a citric acid or vinegar ? I hear they build deposit in the tubes. glad no repair bill for you or "landlord"
 

davidcom

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Hello all. Well, I guess I celebrated too soon. My hot water stopped flowing again this morning. I have no idea why it started working and then stopped again. Ugh.

I thought I'd give this update in case anyone had any suggestions, knowing what I've done so far.

@Jeff H Young the house was built in 2016. I've owned the house for 3 years. I had never flushed it. The reason is because I didn't even know that was a thing. I don't know if the previous owner (who bought the house new) ever flushed it. But I doubt it.
 

Jeff H Young

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Hello all. Well, I guess I celebrated too soon. My hot water stopped flowing again this morning. I have no idea why it started working and then stopped again. Ugh.

I thought I'd give this update in case anyone had any suggestions, knowing what I've done so far.

@Jeff H Young the house was built in 2016. I've owned the house for 3 years. I had never flushed it. The reason is because I didn't even know that was a thing. I don't know if the previous owner (who bought the house new) ever flushed it. But I doubt it.
Good Luck with it . around here they recommend flush yearly , thought about getting a set up to flush with but never have. Perhaps it needs flush but would only be a guess , If a plumber came to service I would expect flush and clean screens first along with diagnosis.
 

WorthFlorida

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Looking at the manual, there is a "water adjustment valve". Is this valve controlled by a solenoid? Is it is then the "Main PCB" is shutting off the water. Why is still a guess. This valve may default to off (close) when there is no power or the opposite or always open until the PCB puts power to the solenoid to close it.

With power turned off to the unit, does water flow on the hot side of any faucet?
 

davidcom

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With power turned off to the unit, does water flow on the hot side of any faucet?

Yes, when I power the heater off, the water starts flowing on the hot side of all faucets. So it's the tank that, when turned on, is shutting off the water flow.

In the manual, under troubleshooting, its says if the water stops flowing, to (1) clean the Cold Water Inlet Filter (which I did) and (2) look at any error code on the display screen. However, there are no error codes showing.
 

Jeff H Young

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I thought if there is no gas fire it wouldnt flow on hot side or a very slight amount. but belive davidcom said no flow
 

Giantsean

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Yes, when I power the heater off, the water starts flowing on the hot side of all faucets. So it's the tank that, when turned on, is shutting off the water flow.

In the manual, under troubleshooting, its says if the water stops flowing, to (1) clean the Cold Water Inlet Filter (which I did) and (2) look at any error code on the display screen. However, there are no error codes showing.

I have a CH240 which is similar. What are you seeing on the LCD panel when the problem is happening? Does it just cycle through supply temp and pressure?
 

RLW

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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.
 

MD1978

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I'll save you the hassle. It's the adjustment valve. Not sure why but perhaps it is slow to open or something and maybes as a fail safe just shut? Mine would just shut right away and I'd have no flow.

I did run a day with dipswitch 6 flipped up. I believe this is full flow so there is no metering going on, which is perhaps why it works...who knows.

It's the adjustment valve. Thanks to the previous threads! You guys saved me some money!

I have a NPE-240A. I don't run the internal circ or external circ. Just in and out with the hot stuff.
 
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GingerMike

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I'll save you the hassle. It's the adjustment valve. Not sure why but perhaps it is slow to open or something and maybes as a fail safe just shut? Mine would just shut right away and I'd have no flow.

I did run a day with dipswitch 6 flipped up. I believe this is full flow so there is no metering going on, which is perhaps why it works...who knows.

It's the adjustment valve. Thanks to the previous threads! You guys saved me some money!

I have a NPE-240A. I don't run the internal circ or external circ. Just in and out with the hot stuff.
I have same issue. Also when I try to descale nothing comes out of the hot water service port.
 
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