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Navien NCB-240 making repeated creaking / groaning / moaning and knocking with burner off

cj5cj5 Member Posts: 10
Hi All,

This morning I heard an odd groaning and knocking sound. Thought it was coming from my neighbor but it was actually from my Navien NCB-240 gas boiler.

I'm waiting for a call back from my maintenance guy but like to short cut the investigation if possible with your help.
  1. It continually makes a creaking noise for 3 seconds then there are 3 knocks.
  2. I tried powering off the boiler but it still makes the noise. If I pull the plug the noise goes away.
  3. I took the cover off to see if I could hear where the noise was coming from. Sounds like the middle or bottom. There is so many different things in there it is hard to tell.
Any ideas what this could be?

Maybe related for a couple weeks I've periodically been getting E109 (abnormal fan operation) codes. I've clean the air filter not that there was much on there but still get the code every few days. Thinking it is the fan but still waiting to hear back from my repair guy. The sound isn't coming from the fan though.


  • NY_RobNY_Rob Member Posts: 1,370
    IIRC I have seen posts where the fan actually degrades and breaks apart. Do you by chance have concentric venting?
  • cj5cj5 Member Posts: 10
    edited July 2018
    I don't have concentric venting. Why do you ask?

    I'm sure the fan isn't making the creaking noise. I only mentioned it, if the codes could somehow be related to the noise. Maybe you just mentioned it as why I'm getting E109.

  • NY_RobNY_Rob Member Posts: 1,370
    Concentric venting sometimes leak exhaust gasses back into the intake air, once that happens it starts breaking down the plastic blower fan blades. Once pieces start coming off the fan and get lodged/stuck in the intake air path it changes the combustion air/gas mix and all sorts of things can happen at that point.

    You might also just need a gas valve adjustment. I got occasional "abnormal fan speed" error codes on my mod con till I re-adjusted the combustion ratio with a Combustion Analyzer. FWIW that was about 1.5yrs after install/commissioning and running perfectly from day one.
  • cj5cj5 Member Posts: 10
    edited July 2018
    So I got one of those automotive stethoscopes that have the wand at the end that lets you pinpoint where the noise is coming from.

    The creaking and knocking is coming from a 3 way valve in the bottom left corner and right about the space heating outlet. It may also be leaking water very very slowly. Hopefully a cheap fix.

    Would there be a cause for the valve to go bad besides it wearing out after 4 years?
  • cj5cj5 Member Posts: 10
    Not that I'm planning on doing it myself but I found a youtube video of someone changing it out.
  • cj5cj5 Member Posts: 10

    Is there any way to manually close the 3 way valve?

    I had the repair guy come and verify that the valve needs to be replaced. Need to wait for the part to come in which is expected.He disconnected the power to the valve so it wouldn't make the noise.

    But now I'm getting E001 which isn't in my manual. Seem like a high temperature cut off. The space heating side is getting up over 200F when I run the domestic hot water. Think the valve is stuck partially open on the space heating side so I guess water is passing through the space heating heat exchanger and gets hotter and hotter because the domestic hot water side doesn't get up to 120F (my setting).

    Just occurred to me that I could set the DHW to 105F which it seems to reach based on the display and run with that till I get the part replaced. Definitely not ideal.

    So is there any way to manually close the 3 way valve? Hoping I can turn a shaft or something.

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