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Navien Vibrating Squeak when it is cold out

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cj5
cj5 Member Posts: 24
in THE MAIN WALL

Hi,

For a few years now my Navien NCB-240 Combi has been making this vibrating squeaking noise when it is starting up space heating. Its like the bearings in the circulating pump needs to warm up. It will do this for about an hour each time the space heating turns on.

It only does it when it is cold outside perhaps <30F.

The past couple years I was thinking it had something to do with flushing the boiler and air being trapped since it would start soon after a flush, but it just started doing it today and I haven't flushed it yet.

I'm pretty sure the noise is from the circulator pump but not absolutely sure.

It's not coming from the inducer fan at the top.

Wondering if this is a sign of pending part failure and which it would be. Since it goes away in warmer weather maybe it is a thing these boilers do…

Any thoughts on this?

Thanks

Comments

  • yellowdog
    yellowdog Member Posts: 287

    Who is telling you to flush your boiler?

  • Intplm.
    Intplm. Member Posts: 2,909
    edited December 2025

    It might be your circulator squeaking at start-up. Take a long screw driver, place the handle at your ear, and the other end on the circulator to get a better idea.

    Maybe post a video here so we can hear it too?

  • cj5
    cj5 Member Posts: 24
    edited December 2025

    Here's a video of the noise. It is a very noticeable noise but not quite as loud as the video makes it seem.

    https://youtube.com/shorts/U2kffScgkes?si=WntxeKyCof8YI5Cp

  • Intplm.
    Intplm. Member Posts: 2,909

    Hmmm. Sounds like the flame. Couldn't hear a squeak.

  • cj5
    cj5 Member Posts: 24
    edited December 2025

    I took a closer look it.

    It's definitely the recirculation pump.

    Since the sound goes away half the time and isn't present when it's warmer outside, I wonder if there is air in the line perhaps lower level zone.

    I've tried bleeding the lines from outside the unit before.

    I there a way to bleed air inside the unit?

    I have baseboards so no method to bleed them.

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