QueBall
New Member
Ok, So I have a 4.5 year old Navien NR-210a condensing tankless heater. (Late 2010)
I more or less did the entire install myself with the help of a few skilled friends either on site or on the phone to give advice.
While I'm not an installer or service tech working on these things all day every day I do talk to one frequently and he has passed on some of his general observations as well as what I have directly experienced with my own system.
I have had a few glitches with mine during the time it has been installed but nothing too bad. My friend who services these tells me the older the unit the more glitches you get. The newer ones are way better than the older units. He says they used to get a fair number of calls for tanks that were installed by other companies that had constant ongoing problems that could be traced back to poor installs. The usual big culprit is not enough gas supply when switching out an old heater. I know in my house it was a major undertaking to get the 3/4" line installed, we had to go through a finished wall to reach the meter but we did a home run right back to the meter and I have never had an issue with gas supply. I know if I just tied into the existing 3/4 line feeding the furnace, fireplace, BBQ, and garage heater it wouldn't have worked very well.
So, the older units like mine definitely have a few glitches to watch out for. The prior CR series are the ones with the most serious troubles. The newer NPE are supposed to be very good, and can even tolerate retrofit installs that the old one would have failed without new gas lines and bigger vents (Though I would still want a full sized gas supply so the unit doesn't have to restrict water flow to match gas supply)
First, a sure fire point of failure on older NR units. The water flow sensor will fail on yours if it had not been upgraded to the newer design with stainless steel internals. The old plastic impeller model will fail if it hasn't already. It's very easy to remove this and inspect it. This part is right near the front on the cold water inlet just before it goes into the heat exchanger with some simple push fit clips holding it in. Take it off and look inside, if you see plastic, get a new one. Navien will likely send you a free replacement if you are still under 5 years. If not buy one and keep it on hand, it's not a very expensive part. When it fails the impeller either gets encrusted with deposits or simply wears out and wobbles and gets stuck. If you remove it and give it a shake and blow into it you can often get it spinning again so the heater works for another hour or another day. But it's a relatively simple part to replace.
So next thing I just had happen is Error number 10 or E010 or 10E 010E etc (for the search engines).
This probably indicates a problem with your combustion air supply. Not enough fresh air, or some blockage in the air vents.
Usually that just meant that air filter on the input air is clogged. So if you get that error you just take off the cover and in the extreme top left of the machine you unscrew the mesh filter and clean it out and start it up again and things are fine. You know this is your problem if you can run the machine with the cover removed (so it draws air from the room instead of outside). You might also have a blockage outside, sucked in some leaves, or trash blocking the air intake. I even had a mouse try and build a nest in the pipe when the outdoor pipe cover fell off. he left in a hurry the next time the unit was used but his debris was still there blocking the air.
In this case it didn't make a difference.
The next thing to check is the cleanout on the bottom for the siphon (white cap near the gas input). This can get clogged up with debris and soot from the burner. If the debris blocks the condensate drain then it will cause this same issue. I guess it creates some kind of back pressure when the condensate drain is blocked.
Last up is the air pressure sensor (APS). This is a black device mounted on the top of the burner with two small hoses coming out of it and it's about the size of a hockey puck. The service manual will tell you that you can check the voltages coming from this device with a volt meter. It gets 5v supply on red and black wires and returns a signal of 0.3v at idle up to about 4.5v when the fan is running at full speed on the white and black wires. I did this test and it showed my APS was reporting what seemed to be a good voltage. Unfortunately it was still bad. The next test is what the Navien support asked me to do. Remove the APS from it's mounting (2 screws holding it in place). Remove the top hose and gently blow into it. You are blowing into a sealed chamber so you should not get any air leakage. If there is air leaking out of the sides or a crack then the APS needs to be replaced. When I blow into my old one I can feel air leaking out of the seams around the sides of the unit. The replacement had no such leak. I tried to temporarily seal the leak but it didn't help, I guess the readings from the sensor didn't match up with the fan speeds which is why the unit wouldn't work.
In my case the unit would try to start up. The fan would start running at moderate speed and then switch to full speed and run continuously for almost a minute before it shutdown with the e010 code. There was no attempt to light the burner. Just before shutting it down when I first noticed it wasn't working it was cycling between purging and attempting to light the burner. I got an ignition error code I think e012 for that event, but it was the same root cause, just a bit different sequence since the machine had just failed and it had not been shut off yet.
So bingo, that was my problem in this case, bad APS.
To summarize my experience, I have certainly had some moderate glitches that have brought the machine to a stop over the 4 years.
-I had the mouse make a nest in the exhaust air line causing E010 errors
-Every spring when to poplar tree and dandelion seeds are like a snowstorm outside my air filter gets clogged frequently causing the E010 error. (I started leaving the cover off during this time of year as it's annoying to clean it every day usually right when you are about to step into the shower)
-I had a problem with the air purge vent on the top of the recirculation pump get clogged with hard water deposits.
-I broke an O ring on that same air purge vent after removing it for cleaning on a subsequent scheduled maintenance (de-scaling)
-Of course de-scaling the unit on a regular basis is important. But my first small pump broke, so I bought a more heavy duty one now.
-I had a faulty water flow sensor
-I had a faulty air pressure sensor
I would suggest if you have a unit of the same age you keep a few spare parts on hand.
I have now started keeping the following supplies
-An O ring kit of various sizes. I would tend to do the descaling on a weekend when the suppliers are closed and I have found out that is exactly the time when you are most likely to break an o ring or develop a leak due to a failing ring. pn: 30009933A
-replacement water flow sensor pn: 30010537A
-replacement APS sensor pn: 30000663A (Probably do not need to keep this part on hand, after you replaced it)
-replacement air purge vent if you have the older recirculation pump. (Newer style has a red cap on the purge valve and hopefully doesn't get hard water deposits collecting in the valve to cause leaks) pn: 30006830A
I more or less did the entire install myself with the help of a few skilled friends either on site or on the phone to give advice.
While I'm not an installer or service tech working on these things all day every day I do talk to one frequently and he has passed on some of his general observations as well as what I have directly experienced with my own system.
I have had a few glitches with mine during the time it has been installed but nothing too bad. My friend who services these tells me the older the unit the more glitches you get. The newer ones are way better than the older units. He says they used to get a fair number of calls for tanks that were installed by other companies that had constant ongoing problems that could be traced back to poor installs. The usual big culprit is not enough gas supply when switching out an old heater. I know in my house it was a major undertaking to get the 3/4" line installed, we had to go through a finished wall to reach the meter but we did a home run right back to the meter and I have never had an issue with gas supply. I know if I just tied into the existing 3/4 line feeding the furnace, fireplace, BBQ, and garage heater it wouldn't have worked very well.
So, the older units like mine definitely have a few glitches to watch out for. The prior CR series are the ones with the most serious troubles. The newer NPE are supposed to be very good, and can even tolerate retrofit installs that the old one would have failed without new gas lines and bigger vents (Though I would still want a full sized gas supply so the unit doesn't have to restrict water flow to match gas supply)
First, a sure fire point of failure on older NR units. The water flow sensor will fail on yours if it had not been upgraded to the newer design with stainless steel internals. The old plastic impeller model will fail if it hasn't already. It's very easy to remove this and inspect it. This part is right near the front on the cold water inlet just before it goes into the heat exchanger with some simple push fit clips holding it in. Take it off and look inside, if you see plastic, get a new one. Navien will likely send you a free replacement if you are still under 5 years. If not buy one and keep it on hand, it's not a very expensive part. When it fails the impeller either gets encrusted with deposits or simply wears out and wobbles and gets stuck. If you remove it and give it a shake and blow into it you can often get it spinning again so the heater works for another hour or another day. But it's a relatively simple part to replace.
So next thing I just had happen is Error number 10 or E010 or 10E 010E etc (for the search engines).
This probably indicates a problem with your combustion air supply. Not enough fresh air, or some blockage in the air vents.
Usually that just meant that air filter on the input air is clogged. So if you get that error you just take off the cover and in the extreme top left of the machine you unscrew the mesh filter and clean it out and start it up again and things are fine. You know this is your problem if you can run the machine with the cover removed (so it draws air from the room instead of outside). You might also have a blockage outside, sucked in some leaves, or trash blocking the air intake. I even had a mouse try and build a nest in the pipe when the outdoor pipe cover fell off. he left in a hurry the next time the unit was used but his debris was still there blocking the air.
In this case it didn't make a difference.
The next thing to check is the cleanout on the bottom for the siphon (white cap near the gas input). This can get clogged up with debris and soot from the burner. If the debris blocks the condensate drain then it will cause this same issue. I guess it creates some kind of back pressure when the condensate drain is blocked.
Last up is the air pressure sensor (APS). This is a black device mounted on the top of the burner with two small hoses coming out of it and it's about the size of a hockey puck. The service manual will tell you that you can check the voltages coming from this device with a volt meter. It gets 5v supply on red and black wires and returns a signal of 0.3v at idle up to about 4.5v when the fan is running at full speed on the white and black wires. I did this test and it showed my APS was reporting what seemed to be a good voltage. Unfortunately it was still bad. The next test is what the Navien support asked me to do. Remove the APS from it's mounting (2 screws holding it in place). Remove the top hose and gently blow into it. You are blowing into a sealed chamber so you should not get any air leakage. If there is air leaking out of the sides or a crack then the APS needs to be replaced. When I blow into my old one I can feel air leaking out of the seams around the sides of the unit. The replacement had no such leak. I tried to temporarily seal the leak but it didn't help, I guess the readings from the sensor didn't match up with the fan speeds which is why the unit wouldn't work.
In my case the unit would try to start up. The fan would start running at moderate speed and then switch to full speed and run continuously for almost a minute before it shutdown with the e010 code. There was no attempt to light the burner. Just before shutting it down when I first noticed it wasn't working it was cycling between purging and attempting to light the burner. I got an ignition error code I think e012 for that event, but it was the same root cause, just a bit different sequence since the machine had just failed and it had not been shut off yet.
So bingo, that was my problem in this case, bad APS.
To summarize my experience, I have certainly had some moderate glitches that have brought the machine to a stop over the 4 years.
-I had the mouse make a nest in the exhaust air line causing E010 errors
-Every spring when to poplar tree and dandelion seeds are like a snowstorm outside my air filter gets clogged frequently causing the E010 error. (I started leaving the cover off during this time of year as it's annoying to clean it every day usually right when you are about to step into the shower)
-I had a problem with the air purge vent on the top of the recirculation pump get clogged with hard water deposits.
-I broke an O ring on that same air purge vent after removing it for cleaning on a subsequent scheduled maintenance (de-scaling)
-Of course de-scaling the unit on a regular basis is important. But my first small pump broke, so I bought a more heavy duty one now.
-I had a faulty water flow sensor
-I had a faulty air pressure sensor
I would suggest if you have a unit of the same age you keep a few spare parts on hand.
I have now started keeping the following supplies
-An O ring kit of various sizes. I would tend to do the descaling on a weekend when the suppliers are closed and I have found out that is exactly the time when you are most likely to break an o ring or develop a leak due to a failing ring. pn: 30009933A
-replacement water flow sensor pn: 30010537A
-replacement APS sensor pn: 30000663A (Probably do not need to keep this part on hand, after you replaced it)
-replacement air purge vent if you have the older recirculation pump. (Newer style has a red cap on the purge valve and hopefully doesn't get hard water deposits collecting in the valve to cause leaks) pn: 30006830A