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Experienced Ears Wanted - Circulator Noise Detectives

LazyDevil
LazyDevil Member Posts: 7
in Radiant Heating
Single level radiant system consisting of four loops in a concrete slab. Four Uponor MVAs in an Uponor manifold. A single B&G NRF22 controlled by a Taco pump relay triggered by the MVA end switches. Circulator is mounted vertically, pumping down, away from the air eliminator. The circulator was replaced 8 years ago and has been running quietly till now.

About 1.5 to 2 minutes after the circulator starts a soft rattle sound starts and slowly builds. A sound recording is attached. Is this a bearing beginning to go out, or cavitation. Why would cavitation start now with no changes in the system. The circulator is moving water from the moment it starts, and the system is heating the townhouse well.

Thanks in advance for any information or hints.

Lazy Devil

Click below to hear the sound:
https://drive.google.com/file/d/161HnF-e7XCc-tgQFAsNn8QQSv762dHRK/view?usp=share_link


Comments

  • HomerJSmith
    HomerJSmith Member Posts: 2,583
    edited December 2022
    I don't know if I qualify, I'm deaf in one ear and can't hear out of the other, but that never stopped me from rendering an opinion. Might be a solder ball lodged in the impeller or volute or maybe a fractured impeller. Pull the pump head off and examine everything.

    If not that, maybe a bad check valve in the output of the pump if it has one.
  • Intplm.
    Intplm. Member Posts: 2,146
    It's great that you have isolation valves installed on that circulator.
    Since you do. Take the circ. off the flanges and look for any debris that may have lodged in the head of the circ. Try running it a little while it's off before putting it back on, and listen for the noise. You probably have something caught in the head of the circulator.
    If you do this, change the flange gaskets before putting it back on.
  • LazyDevil
    LazyDevil Member Posts: 7
    I removed the circulator. The volute was choked badly with rust concretion. Cleaned the bulk of this off, and reinstalled with new flange gasket rings.

    I think it was cavitation which started slowly as the reduced flow built up back pressure. The cleaned circulator is running silently and all seems in order.

    Thanks to HomerJSmith and Intplm for their suggestions. And of course, thanks to HeatingHelp.com as a repository of knowledge.

    LazyDevil
    Intplm.

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