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Noise issue w/ Lochinvar boiler
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