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Strange pop/bang noise in condensor loop


Myself and mechanical company having an issue with a secondary condenser loop (RETURN SIDE ONLY) We brought in a SONIC imagine camera to pint point the area and this is what it came up with. Here are some facts on the system.

1) The water temp ranges from 72 supply - 82 degrees return
2) We have replaced these expansion joints already
3) Water treatment is good
4) Pump operation verified Okay
5) System supplies heat pumps with condenser water
6) During winter- we inject hot water into the cold loop (I thought it was related to that but the problem continues into cooling season)
7) Some of the best mechanical minds have looked at this and have not been able to solve.


  • DanInNaperville
    DanInNaperville Member Posts: 40
    edited June 2018
    Any chance a check valve somewhere in the system (maybe built into a pump) is causing sound to be conducted to this location? Does it sound anything like a water hammer? Is there sheet metal somewhere that could be oil canning? Have you used the stethoscope with a stick on it trick (or held a long screwdriver to your ear) to try to pinpoint the sound? I'm not sure that a remote sensing sonic imager is that precise. Was it calibrated to a known sound source just before use? It could be that the sound sensor pattern and the image are displaced a few inches from each other. It's not like a thermal imager where you're able to view direct source. A couple degrees of arc one way and the sound is coming from the wall. A couple degrees the other way and the sound is coming from the duct. A couple of degrees up and it's coming from that coupling.

  • LFsuper
    LFsuper Member Posts: 29
    Hi, Thanks for your response. It does sound like water hammer a little. Thanks for the great info. Only checks on this system are after the main pump on supply side. The heat pumps connected to the return would have checks/flow valves which is interesting.
  • ratio
    ratio Member Posts: 3,543
    How loud? How often? Can you post a recording of it?

    Looks like new residential work? Homeowners complaining?

    What's between the flanges right above the hot spot? I'd be looking at that pretty closely even if the sound is unequivocally located as shown: I can only imagine a few scenarios where a straight piece of pipe can make any kind of sound.

  • LFsuper
    LFsuper Member Posts: 29
    Hi there, Its new constrction. 65 story hi rise. noise is on return line on a few different apartments. I will find a recording. Thanks.
  • LFsuper
    LFsuper Member Posts: 29
    Unfortunately I cannot upload an audio clip.
  • GBart
    GBart Member Posts: 746
    Obviously something is wrong, the only thing I can suggest is out together the factory recommended piping for each system, pumps, heat exchangers, wshp's and find what is wrong that way, as you state the noise is in different areas and on the returns so the return piping and perhaps those checks are the focal point?

    this gives some variations of designs and situations, since it's happening in different areas whatever was done wrong was repeated