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Noise issue w/ Lochinvar boiler

zepfanzepfan Member Posts: 292
We are having a noise issue with a Lochinvar boiler model# RBN 180. It is one of three of this same model installed in 2004. The three boilers are piped in parallel. One of the boilers makes a humming noise that is noticable throught out the building only when it is firing. We have disassemble the boiler cleaned the outside of the heat exchanger, soaked the burners in hot water and detergent brushed them out, and then reinstalled them
in the boiler. None of this helped. The noise continues. We took the flue pipe apart, check the chimney for obstructions, and the flue pipe that connects to the boiler. The gas manifold pressure is fine, right at 3.5” All three boiler’s combustion was checked in October but I am thinking that the only other thing that could be causing this noise is either an air/fuel ratio issue, or water flow. The noise is only there when the boiler is firing. If the boiler is up to temperature, with it’s circulator still running the noise stops as soon as the burner goes off. Any assistance would be much appreciated. Thanks to all


  • IronmanIronman Member Posts: 5,626
    Do you have any CSST in the gas line?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • zepfanzepfan Member Posts: 292
    The final connection to the boiler is done in csst. The mains are all black pipe with the last 6" connected to the boiler done in csst
  • DZoroDZoro Member Posts: 1,035
    Is it the last one to fire, or do they rotate firing? Probably worth the effort of removing the csst.
    Did it just start this trick or has it always done it?
  • zepfanzepfan Member Posts: 292
    The noise just started. It is the lead boiler of the three, and they do not rotate. The other two don’t make this noise and they have the same csst hookup.
  • DZoroDZoro Member Posts: 1,035
    I would change it to hard pipe. Being first in line to fire he is getting full gas pressure and causing some turbulence in the pipe.
    But it is still a WAG at best, worth the effort IMO.
  • if think the noise is being carried by the water pipes, could it be a kettling noise, from the fin tubes being limed up on the inside.??
    have you checked the water side of the tubes in the recent past?
    i have been involved with some fin tube boilers making noises while burning and it was because the tubes were limed up.
  • zepfanzepfan Member Posts: 292
    thanks to everyone who commented on this post. If it was lime scale on the tubes I would think that the noise would be present then anytime the boiler is up to temperature with the circ. running. The noise is only there when the burner is on. It goes away after the flames have gone out
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