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metallic noise from circ area and from baseboard

Nom_Deplume
Nom_Deplume Member Posts: 91
Hello...our hot water heating system has developed a faint but increasing "tinkling" metallic noise from some of the baseboards. The same noise can be heard at the circulator that drives these baseboards. In a stupid homeowner move, I replaced the circ (I had an extra one). It made no difference.

However if I turn the circ off while leaving the other circs on, the noise stops.

(a) Is the next possible culprit the check valve that I know is built into one of the isolation valves?

(b) How does one tell which valve has the built-in check valve?

(c) Why do I need a check valve at all? Our primary/secondary system has three circulators, i.e. two zones. The zones are so well-matched that I use one stat for both zones, with no over/under-heating. In other words the primary circ and two secondary circs all run at the same time. They run 12 or more hours a day (outdoor reset) for most of the season. No DHW. So why do I care about ghost flow?

Thank you!

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    Possibly a small amount of air in the system. Check the pressure and the expansion tank and any air removal device.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Nom_Deplume
    Nom_Deplume Member Posts: 91
    Thanks for the suggestion!

    There is a Honeywell Supervent, but it is on the primary, and the noise is in a secondary (no noise if I run everything except this one secondary circ).

    I have drained lots of water from the baseboards and do not know what else could be done to remove air.
  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    If you drained water from the baseboards and didn't keep the pressure up while you were doing it, you may have introduced air. It's possible that -- eventually -- the Supervent will do the job, but you may have to actually purge the loop.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Nom_Deplume
    Nom_Deplume Member Posts: 91
    Homeowner, but not so ignorant as to drain without leaving the fill valve open.

    PS I figured out the answer to my question (b)---one valve has a longer body than the other, and it must be the one with the built-in check valve.
  • mattmia2
    mattmia2 Member Posts: 9,576
    introducing fresh water in to the system will introduce the air dissolved in that water so the air elimination will need to remove that air.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,455
    If you have a flow check valve they usually have a lever or screw co you can open it and see if the noise goes away
    mattmia2
  • Nom_Deplume
    Nom_Deplume Member Posts: 91
    edited April 2021
    Just an update. Of course it was not air making the metallic noise. The check valves built into pump isolation valves do not have any built-in way to lock them open. I jammed the check valve open with a small pellet made of aluminum foil. Noise is gone. I realize the foil pellet is slightly blocking the flow. I will change the entire shutoff/check valve during the summer.