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Loud horn noise on Lochinvar Cadet the day after inducer motor replacement

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dhw_probs
dhw_probs Member Posts: 26
in THE MAIN WALL
I just had a tech in yesterday to replace the inducer motor on my Lochinvar Cadet 120k BTU.

Since then, I've had a new problem: As often as about every 10 minutes it will give off a loud horn noise like a semi truck, lasts for about 5 seconds. Sometimes it will go hours without doing it, then do it often.

It seemed like it was doing it when firing up, and I was able to fairly reliably reproduce it by hitting the reset button and waiting for it to come back up. I was watching through the little glass hole where I can see the flame, and the noise happens about 1 second after the flame ignites.

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  • HVACNUT
    HVACNUT Member Posts: 5,841
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    Is this natural or LP gas? I recently had a call for a horn noise where the installer didn't install the LP orifice. This wasn't a Lochinvar but its something to check. The tech had to remove the gas valve to replace the blower and the orifice is right there.
    kcoppZman
  • dhw_probs
    dhw_probs Member Posts: 26
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    Thanks to both replies... Sounds like it's nothing user-serviceable, so I'll have to get them back.
  • Ironman
    Ironman Member Posts: 7,376
    edited January 2021
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    Is the any CSST in the gas line? If so, that’s the SOURCE of it. Having the burner not properly tuned to the richer side of the manufacturer’s specs can cause the resonance when CSST is used.

    If proper tuning doesn’t alleviate the problem, then removing the CSST, or using a larger diameter should.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Zman

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