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NTI FTVN Error Code 104

skiploder Member Posts: 6
Just had an NTI FTVN installed around thanksgiving…replacing  a 20 year old munchkin that ran flawlessly (I know) since the house was new.  Boiler runs the DHW and floor radiant heat.

The NTI ran perfectly for two weeks  then started throwing a 104 code every 24 hours.  

That lasted a week while the tech worked out scenarios with NTI…. then the frequency increased to every few hours for two days.

NTI sent out a new harness and sensors for the supply and return lines which did not help the issue.  Went back to throwing the 104 code every 24 - 36 hours when switching from CH to DHW or vice versa.  If you shut down the water heater and run central heating or vice versa it will run without an issue. 

NTI sent out a new pump and diverter valve a few days ago, and while awaiting parts the boiler ran five days without an issue….then began throwing the 104 code every 6 to 8 hours again.  Waiting on the holiday to be over for the new parts to be installed.

Both NTI and the tech seem to think it’s a faulty diverter valve. Based on the group’s collective  experience with boilers…. does it seem like they’re on the right track?


  • Tom_133
    Tom_133 Member Posts: 879
    It would be very useful to see a pic from 5' back or so. Sometimes its how its piped that makes that error code come up.
    Montpelier Vt
  • skiploder
    skiploder Member Posts: 6
    I’m out of twin right now.  These are pics from the install:

  • skiploder
    skiploder Member Posts: 6
    Meant to say “town”.
  • Ironman
    Ironman Member Posts: 7,339
    edited December 2022
    I have the same boiler (HTP version) in my house and we install a lot of them.

    A104* error code is insufficient circulation or low water pressure.

    Your boiler gauge is showing sufficient water pressure.

    Air in the lines can cause insufficient or no circulation. Have all of the circuits been properly purged off air?

    You've replaced the wiring harness and sensors.

    There could be an issue with the internal circulator.

    These are the four things listed in the manual’s diagnostic flow chart.

    I can’t follow the piping under the boiler in your pics; however, the boiler MUST be piped primary/secondary when multiple zones circulators are used like you have. If not, you could have circulation issues.

    Better pics would help.

    I suppose it could be the diverter valve, but I’m somewhat doubtful: if the valve was sticking in either position, you’d still have flow to that circuit.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • skiploder
    skiploder Member Posts: 6
    It’s primary/secondary….With domestic hot water primary and radiant heat secondary it’s been purged and bled and it’s reading about 15 psi on both gauges.

    I guess what’s confounding even the NTI techs is that it’s sporadic….it’ll run two weeks with no issues and then go through a two or three day tear where it throws a 104 fault every 6 to 8 hours and then goes back to having no issues again.

    NTI has been great….they spent a lot of time on the phone with the installer , they have looked at photos of the install and deemed it per their specs ….they literally sent us out everything but the motherboard to replace … The sensors, the harness, the diverter, and the pump.

    When I get back to the house I’ll post some more detailed pictures of the set up. Thanks for everybody’s comments
  • skiploder
    skiploder Member Posts: 6
    Resolution update:  It was a sensor issue.  The finally admitted they had a bad batch of them and sent us a new set at the end of January.  They confirmed the issue by monitoring it remotely for about 10 days.  Knock on wood, the boiler has run flawlessly since then.

    Here's the problem...they refuse to reimburse us the money for the installation of all the parts they sent.  Despite having email communication with their tech staff wherein they said the install was completely correct, plus and admission that they had a bad batch of sensors, they are fighting the installer on the reimbursement of his costs to install the diverter, the circulation pump, the harness and the sensors.  

    We literally have an email from their techs stating all of this.....not an honorable company in my opinion...considering our installer had originally told them he was consistently getting severely fluctuation readings from the sensor.

    The tech line was great to work with and we had one tech from beginning to end that always returned calls and was polite, and spent a lot of time with the installer.  The customer service and warranty department - different story.  
  • hot_rod
    hot_rod Member Posts: 21,807
    Seems odd if they knew there were bad sensors out there, that should have been the first shot from the parts cannon?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • skiploder
    skiploder Member Posts: 6
    They apparently sent them out with the harness, but they were still in the middle of their bad batch run.