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Navien NR-240A heating issues

haukeg Member Posts: 23
Hello, thank you for reading my post.

--- First off:

I am a home owner with a little understanding on the setups for tankless and radiant heating, but do not claim to be a contractor or installer. I have been experiencing a lot of issues ever since we moved to a tankless/radiant setup for our home from a tanked/forced air setup about 4 years ago when we did a major home remodel. We had our Navien CR-240A + HeatBox installed by a company that turned out to be incompetent (since has closed for business and under subsequent inspection by reputable installers has been determined to have made a number of mistakes in the pex installation for the raidant heating). However, aside from the installation issues, we have experienced a number of issues with our Navien appliances...

After the initial install of our CR-240A (taps often would not return heated water, we had some leaking from bad fittings, etc.), we had a number of issues that required a complete warranted replacement.

We now have a NR-240A unit and we were excited to have problems behind us. However, we have had repeated issues with the heat level of our domestic water. Each time I call Navien for help, they suggest my issue is related to debris getting into the flow sensor and preventing it from triggering properly. The process to take apart the fitting which holds the flow sensor to "blow" it out clean is arduous, requiring drainage of the system etc., and has not solved the problem.

I have alos checked my HeatBox settings to ensure the temp is set high enough for my domestic supply (set to around 120 degrees). I do have my heater setup with a re-cir on a timer and I dont notice much difference from when the issue happens within or our of the circ running. My replacement unit is now out of the 1 yr warranty as well.

--- Here is the bottom line of my issue:

When we shower, it often starts out moderately warm (not hot) for about 2-3 minutes then goes cold. I have to turn off the hot water service and wait 10 seconds or so then turn back on, after 20 seconds it gets hot again.

My assumption is something (like the flow sensor suggestion from Navien help) is not triggering the domestic heating setting. I have run down to check my unit (in my basement garage) when the issue comes up but find the icon on the LCD with the faucet showing - indicating it sees the call for domestic hot water.

This extreme situation (having to turn on and off) is also fairly recent, it seems like the cold weather might have triggered it? I have wondered if the HeatBox is to blame, or maybe the demand on the radiant system is affecting thins since its more in use with the weather? Before the turn on/off situation our main issue was that it never seemed to reach full temp (the set 120 degrees) - and was a luke warm unsatisfying shower.

Unfortunately the LED read out for temp/status on my HeatBox is starting to fail (faint LED segments) so I am not able to accurately diagnose the temp of water being received in the HeatBox for domestic.

I dread calling Navien again to get help on this as they dont really seem to like home owners calling. The new company that I have servicing my house doesn't work much with Navien and do not really think they are a good line to go with,s o they havent had much to offer. The best advice I get from them is to change the unit out for a more reputable make, which is costly.

--- I know this is a fairly open ended post, but:

I am desperate to find some advice/help on this situation. My hope is that someone here might have a thought on why my setup would be acting this way. I have had a lot of issues with my overall heat setup since my remodel due to the bad install (other issues I wont waste time stating) and this decision has been the worst headache of my home life since my remodel. I now have kids with cold baths and a wife who is fed up - any help appreciated before I have to swallow the bitter pill to buy a new unit.

Thank you!


  • Ironman
    Ironman Member Posts: 7,225
    More Issues

    Can you post some pics?

    It's difficult to try and diagnose what's wrong with just a description of the symptoms and not being there hands on.

    On thing that is a definite issue is the use of the tankless for space heating. It's not designed or controlled to operate with the Delta T or flow rates required for space heating, nor is it approved for such. This may be the source of your problems if the return from the radiant is sending warm water back to the unit.

    Also, a re-circ line should not be connected directly to it as that will cause the same issue.

    Navien makes a combi unit that IS designed to do both, model CH. That would have been the correct choice. We've had no issues with these. They work great if installed correctly with proper system design.

    The biggest part of any system is the designer/installer; he's 98% of the equation.

    Where are you located?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • haukeg
    haukeg Member Posts: 23
    Photos and more

    Bob, thank you for your reply.

    I am not using the NR-240A alone for space heating, the unit is combined with a "Heating Box" ( http://www.rural-energy.net/docs/om_nHeatbox.pdf ) which acts as the heat conductor to the closed loop radiant setup. This was the setup approach before the CH units were available.

    I have attached basic photos of my setup, I hope it helps. If you need specific shots of any part of my system I would be happy to tae more specific ones.

    I totally hear you on the instal/design being incredibly important. As I stated, the original installer was a bit incompetent and we had to have a second qualified installer come make repairs/modifications to the setup to fix issues. Most of those issues have been resolved, however this unreliable heating of domestic water has been variable and persistent.

    To me the, situation seems likely to be the unit not accurately acknowledging when domestic service is being requested. Almost like it loses flow telling it it is being requested (which is how I understand the unit determines the request, by detecting the draw of water when a tap is open). I have tried troubleshooting and watching the Navien LCD controller to see if it shows the icon for domestic water (the faucet icon). It has been inconsistent in its behavior. I tired again tonight by having my wife run our shower and it stayed hot tonight. I will try again in the morning when we typically see the on/off solution issue. I wonder if it could be due to the increased use of the unit now in this cold weather, where the Heating Box would be more regularly calling for heated water to supply the space heating loop. But again, its a strange issue that isnt obvious. No error codes, just random cooling down or shutting off of the heat when we shower or wash dishes.

    I know tere are many successful installs and happy customers and I really want to have this setup work. We really love on demand service and believe in the approach, but the buggy behavior we have found with our Navien (both units) has left me frustrated.

    Thanks so much for your help, please lend me any thoughts or options for solutions.
  • Ironman
    Ironman Member Posts: 7,225
    Heat Box

    The "Heat Box" setup may still b e the issue.

    As I stated, a tankless, any tankless, is not designed or controlled for spacing heating. It's looking for a very high Delta T (77* to be exact). It's looking for an inlet water temp of about 50* to be heated to 125*. That's how it's designed. Its modulation is there to mach varying gpm, not varying inlet temp (for the most part). The heat box is returning warm water to the inlet of the tankless which is something it doesn't want; it wants cold water. If the water is too warm, or the flow is too low, the tankless won't fire.

    The Heat Box is an after-market attempt to make a tankless do something it was not intended to do: space heating.

    This issue comes up at least a couple times a week on here and many of us see it in the field regularly. My response is always the same: "If a tankless could take the place of a boiler, there would be no need to make boilers".

    The Navien combi is actually a boiler that employs a plate heat exchanger to heat domestic. It works great for heating both because it was designed to do so.

    If you'll post your location, we may be able to recommend someone locally who can help you.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • haukeg
    haukeg Member Posts: 23

    Thanks for the explanation Bob, that is interesting. I did not know that was the case and it makes sense. I had hoped my solution would not be to go with a full replacement of my Navien and Heat Box for a combi unit, but in the end if that is the only solution I may have to. In that direction, could you recommend what brands/models of on demand boiler combo units you have found to be best? Do you prefer the Navien Combi, or others?

    I live in Seattle, Washington. My current service company is Custom Floor Heating (Brian the owner has been fantastic to work with). However they do not work with Navien much and do not prefer them. We had worked with another company for the install but they closed down and were incompetent. Custom Floor came in and fixed a bunch of their mistakes/designs.

    --UPDATE on the behavior:

    So I had my wife run the water on and off a number of times while I stood by my Navien to see what it was doing. Here is the basic cycle of events:

    -No domestic water on - the Heat Box is calling for heat for space heating and the Navien is supplying hot water fine to that unit. The LCD control shows the Energy Save icon and Re-circ icon.

    -Domestic tap is turned on, the Heat Box shuts off as domestic takes priority. However, it seems that Navien doesn't recognize the domestic call. Now the LCD just shows the Re-circ icon. Water tem to the domestic tap plummets in temp (as the Navien isnt heating water).

    -Shut off the domestic tap for 10-15 seconds. While the tap is off, the Heat Box calls for water again and the Navien kicks back in.

    -Turn Domestic water on again (after 15 second in line above) and the Navien does supply Hot water to the domestic tap just fine.


    So it seems to me that somewhere between the Heat Box doing its thing, heating the space, and then a domestic tap turning on, the Navien doesn't recognize a domestic tap is on. But shutting off and back on triggers it. So maybe a sensor isn't functioning right, or as you suspect the Heat Box is interfering. I dont see the Faucet icon on the LCD very often, which I understand to be the sign it sees a domestic tap call (which doesn't show even when its working to supply hot water to domestic).

    In any case, the Heat Box is working fairly well for space heating, and the Navien hasn't been shutting down in that service mode - as you suggested that it might not like a return temp of hotter water (though I cannot confirm either way). It really seems like the transition from sending water to the Heat Box vs. the Domestic causes the Navien to shut off.

    Thanks again very much for your help.
  • RobG
    RobG Member Posts: 1,850
    Combi Unit

    Rather than go with a combi unit you could put in a properly sized Mod-Con wall hung boiler for your space heating needs (where your Heatbox is now), and dedicate your Navian tankless for domestic hot water (what it's designed for). The Navian will put out more hot water than any combi unit, then you would not lose your total investment in the system. Down the road, you could put in an indirect water heater off your mod-con if you choose not to replace it with another tank less. Tankless water heaters, when installed correctly, work great.   

  • haukeg
    haukeg Member Posts: 23
    Interesting Idea

    Rob, fist off, love your profile photo. Thanks for the idea. Can you explain a little more what your suggesting, what a Mod-Con is and any links to info on such devices?

    Thats an interesting idea, however I am not sure if it will solve my Navien issue where it isn't seeing the call for domestic hot water. But I assume it could, this issue has only been happening recently when the weather has gotten colder - so I suspect its because my Heat Box is calling for water so much right now it is fowling up the domestic calls (where before it would be sitting idle when a domestic call comes in).

  • smklin
    smklin Member Posts: 69
    space heat off

    Maybe turning your space heat off see if that will effect anything.
  • haukeg
    haukeg Member Posts: 23
    Great test idea

    Thanks, I will try that! Then I can narrow down the issue to being the Heat Box being on while calling for Domestic hot water. Cheers!
  • Ironman
    Ironman Member Posts: 7,225
    Paul Pollets...

    is in Seattle. I would highly recommend him.

    His posts are all over here on the wall.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,225

    Also, try turning the re-circ. off. It will cause the same issue.

    There's one other option if replacement is necessary: you could install the Navien combi unit and keep your CR tankless. They can be twinned for domestic which would give you twice the domestic capability that you now have.

    I'm like Rob though; the best setup is a dedicated mod/con with an indirect.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • haukeg
    haukeg Member Posts: 23

    Great idea, if I have to go that route, I like the idea of gaining something - more water capacity is a nice benefit as we run out easily if to many things are using water at once. That might also allow me to go a more economical route with a lower end Combi (CH-180 vs. CH-240 for example) if I dont rely on it for all services?

    I will try shutting off the re-cric as well and will post my finding for others. Thanks.
  • haukeg
    haukeg Member Posts: 23
    Thank you

    I will look him up when/if I need to make a service call.
  • HDE
    HDE Member Posts: 225
    Call Navien and tell them

    That the domestic hot water priority switch is not functioning and see what they say.

    Do you have a manual with a component breakdown? it's in the front, low in the cabinet
  • Ironman
    Ironman Member Posts: 7,225


    Why would a single function (domestic) unit have a priority switch?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • haukeg
    haukeg Member Posts: 23
    Getting Closer

    Ok, I think I am getting closer to the root of the problem (thanks for the tips so far):

    This morning I shut off all thermostats so my HeatBox would not call for water, then took a shower and to my delight I had a nice steamy long shower for the first time in a while!

    I then went down and checked to see what the Navien LCD showed when a tap was on and in this case (with the Heat Box off) the Faucet Icon was showing when a tap was on, which is expected. However before, when the Heat Box would be on and then a tap would call for water, that icon DID NOT show.

    My assumption is something is not triggering whatever sensor tells the Navien a domestic tap is on if the tap turn on when the Heat Box is on.

    If anyone can offer any other suggestions or ideas why this would be happening, please let me know. I plan to call Navien soon to discuss with their tech support. Hopefully there is a solution that doesn't require a replacement of the Heat Box, but perhaps thats the down side of that tech.

    I will also try turning the Re-Circ off (while letting the Heat Box run) and testing that affect on the condition.

    Thanks again to everyone's help so far, I really appreciate it.
  • RobG
    RobG Member Posts: 1,850

    It sounds like what HDE said above, the domestic hot water priority switch may not be working. What that does is automaticaly shut off the heatbox on a call for domestic hot water. Thats what you are doing manualy now.

  • haukeg
    haukeg Member Posts: 23

    Hoever, the Heating Box DOES shut off when a domestic call is made. If the Heating Box is running and a tap turns on, the Heating Box definitely shuts down but it then just seems like the Navien shuts off (doesn't fire up for the domestic call - no faucet icon like I said above).
  • HDE
    HDE Member Posts: 225
    edited January 2013

    Its nickname was "boiler room in a box"

    It consists of SS plate heat exchanger(s), pumps control, mix valve. Putting everything in a box, contractors were building on their own to add supplemental heat to a basement, addition, etc. off of a tankless. Personally I thought it should be a secondary heat source only for addons, additions, etc.

    The heating box was designed as an ancillary item to a tankless of any brand, not just Naviens. Its internal pumps would pump water through the tankless next to it creating heat to be exchanged via a plate heat exchanger for the closed loop heating side. The domestic connections are made to the heating box, so when domestic demand is sensed it stops the heat production for the heating side and goes into domestic priority. This is so no potential BTU's are stolen from domestic production allowing near tankless performance to be used.

    I suspect the OP's problem is sensing the domestic flow.

    Navien Heat boxes are no longer made, phased out by their combi but there are a few manufactureres still making a similar product

  • tim smith
    tim smith Member Posts: 2,708
    Re: Navien problems

    Haukeg, you are welcome to call me at 206-283-1234 if you like to discuss the problem. We are on Queen Anne hill in Seattle.  We do a lot of repairs on combi units but do not install them generally as we are fans of true boiler systems.  We can probably help although I will tell you it is not always a  quick simple fix.  We also call tech support to get info on the internal components when problems are not evident and basic checking of flow and components does not show problem. The info they have at their fingers help us with diagnosing and fixing the problems.  Our company is Reed Wright Heating
  • haukeg
    haukeg Member Posts: 23

    Hello, I wanted to give an update on my situation:

    I have tried diagnosing my temperamental domestic hot water behavior with little consistency. I tried killing any thermostat calls which tells the Heating Box to call for water and then turned on my DHW tap with varying results. Sometimes the Tankless would fire up and deliver hot water as expected (showing the tap icon on the LCD), but most times it would sit idle and never register the DHW call. I then tried killing our re-circ cycle and that also gave inconsistent results.

    When the Heating box is running and a DHW call is made, it does shut down the Heating Box as expected, but the Tankless inconsistently would deliver water. I watched the Heating Box's LED which tells the water temp going out to DHW and coming in from the Tankless, and the results were odd. Usually the DHW call would deplete any hot water in the system, going from ~110 degrees down to the 80's before the Tankless would kick in to supply hot water (if it does at all).

    I am not sure if the Heating Box is what dictates when the Tankless should kick in or the Tankless is just waiting random amounts of time before it kicks in (again, if it does), but it has been unpredictable. AS described in earlier posts, it seems to help to shut off the DHW call for 5-10 seconds and then turning it back on, then the Tankless seems to work as expected.


    So I have consulted with my heat guy on options, that will be my next post.
  • haukeg
    haukeg Member Posts: 23
    Possible next steps

    After consulting with my heating service guy, he is recommending a full swap out of the Heating Box and the NR-240A for a Triangle Tube Prestige Trimax Excellence unit. He has had good history with that make and is confident it will cover both my DHW and radiant space heating needs much better than the NR-240A + Heating Box setup I have now. He feels the flow rate for my space heating has been inadequate due to the flow rate of the Heating Box being small. He also feels the demand on the Navien is too much to supply DHW and space heating (which many of you had suggested above).

    He is quoting me at $8500 for the removal of the old units and installation and plumbing to istall the new Triangle Tube boiler. He said my current setup will make the swap pretty straight forward (I already have drainage setup for condensation, all my plumbing for my space heating and DHW are already setup, etc.).

    Some questions for you all:

    -Does this estimate seem on target?

    -How do folks here feel about Triangle Tube?

    -Is there any market for me to sell my used NR-240A and Heating Box units after this new install? The NR unit is just over 1 year old and the Heating Box unit is almost 4 years old. If so, what is the best route for that?

    This has been a frustrating conclusion to come to. I have now spent quite a bit of money and energy trying to get my setup running well over the past 4 years, but it seems the overall design was just poorly done. What a bummer.

    Thanks for all the tips along this thread.
  • Heat box failure

    We do not discuss prices here, as there are so many variables.

    Even more important than what you spend is the value you will receive from a boiler which is chosen properly, and installed correctly by a competent hydronic expert.

    The present heatbox installation has obviously been a dismal failure, and was probably installed to a price, rather than to a performance. Much of your system will have to be corrected, as the new boiler goes in.

    Make sure you have confidence in the installer, and that parts for the boiler will be available from a stocking distributor in your area.--NBC
  • Smartalex
    Smartalex Member Posts: 1
    Next Steps

    We have a similar set-up in our house in Toronto, with a Navien Heating Box and Navien tankless water heater NR-210. The Heating Box is now out of warranty and it's no longer heating our house. We just tried replacing one of the pumps, while the other pump was replaced under warranty, but it's no longer circulating the heat but makes noise instead.

    In any case, it looks like our Heating Box needs to be replaced and we have received a couple different quotes. I am curious to know what haukeg decided? What did you end up going with and how is it working for you? As for us, some are suggesting that we swap our Heating Box for a Combi unit and we could keep our Navien Water Heater. Others are suggesting we go with a boiler with a separate hot water tank, reverting back to more dependable technology. Any thoughts or opinions would be much appreciated.
  • johnmerritt
    johnmerritt Member Posts: 2
    New poster here. Came looking for answers to very similar questions. I won't run through the litany of problems I've had with my Navien... would take to long and might result in profane language. However, my current problem is the same as the current posters. I also use my unit for space heating with a Lifebreath unit and DHW. After reading and trouble shooting I tried turning off my lifebreath so that wouldn't be a factor. With the Lifebreath off my DHW temp fluctuates wildly to the point that showers are a misery. Too hot one second and cold the next. There are no error codes showing up ... sometimes the unit shows that DHW is demanded... sometimes not. Doesn't seem to be any real rhyme or reason. I'm guessing that it may have to do with the flow sensor... but I fear trying given that it's winter and if it totally breaks down I will freeze to death in short order. The unit, when an error code ... E12.. doesn't shut down unit all together, is able to heat the house. That error , BTW, is easy to clear by simply unplugging the unit for 30 seconds and then plugging it back in) The house is small and built with SIPS and so doesn't require much in the way of heat even here in Michigan, so I'm guessing that enough BTU's (probably again at wildly varying temps) are making it to the lifebreath to heat the house. My question is how do I clean the flow sensor. I'm handy with and have just about every tool but I would dearly love to know EXACTLY the steps to take. Can anyone provide a link ? Thanx, John.
  • SWEI
    SWEI Member Posts: 7,356
    Has anyone done a heat loss calculation on the house?

    Is the Navien heating your DHW satisfactorily?

    I'm not intimate with the Lifebreath line, but they look similar to the other residential HRV's and ERV's I've seen. Does yours have a hydronic reheat coil?
  • johnmerritt
    johnmerritt Member Posts: 2
    OK ! Finally did something that worked ( probably should have known it but didn't). I flushed out the Navien with 2 gallons of vinegar for three hours and it obviously needed it. Found a good youtube video that showed how to hook it all up. All I needed was a submersible pump ($89) and two 8ft washing machine hoses ($22) and the vinegar ($10). Hooked it up and let it go. Problem seems to be 90% fixed ( still runs colder for a few minutes occassionally)... but showers are good again and the wife has stopped threatening to hang me. I plan on this type of cleaning every 6 months unless anyone here knows a good reason not to. Hope this can help someone else.
  • gennady
    gennady Member Posts: 839
    Water heater cannot be used for for heating. Period. Get a boiler. And Navien? Seriously?
  • jonny88
    jonny88 Member Posts: 1,139
    HDE do you have a response.Honestly you are familiar with Navien as seen through your posts,if a perfectly plumbed NCB is installed what is the life expectancy allowing for a service every year?Would love an answer as I am getting beaten up by these Navien one day wonder installers.Note I said installed correctly which I see rarely.Thanks.
  • haukeg
    haukeg Member Posts: 23
    Reporting back on the change I made to the Triangle Tube (as stated earlier in this post). I am happy to report that it has been a huge improvement. I have never had an issue with the Triangle Tube unit. It can run hot water til the cows come home and has kept up with house heating needs nicely (although I have found the plumbing setup for that is also incorrect - the guy that set us up originally was incredibly incompetent and now out of business). Anyhow, just wanted to voice my disdain for Navien and my pleasure with Triangle Tube for any others looking for help on this. Although I cannot speak to any more recent Navien builds...
  • kcopp
    kcopp Member Posts: 4,305
    Thanks for the Update. Which Triangle Tube Model did you switch to?
  • haukeg
    haukeg Member Posts: 23
    Triangle Tube Prestige Excellence 110. It’s incredibly quiet and pumps out endless hot water.