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I recently bought a brand new house which has new AC unit. but the outdoor AC unit constantly makes the loud humming noise which also vibrates refrigerant pipe. see the attached video link. what could be the problem?? Is this humming noise is normal??

https://drive.google.com/drive/folders/1arvnQP6-KxBKUqhklRQq9QCtNPBq9Nyh?usp=sharing

Thank you in advance

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  • you seem to be far too focused on the "is it normal" instead of "how do I fix it" part of the question. Since this is a brand new house and you've already had the HVAC tech out to look at it, get a sales person/customer service rep to come to your house and sit in the living room. When the AC kicks on ask them if this is the level of noise/vibration they would accept in their own home. If they still say it's normal... [con't]
    – FreeMan
    Commented Jul 6, 2020 at 15:38
  • ... remind them that it's not what you had in your previous home from them and indicate that you hope that this isn't the direction their overall build quality has taken since the last house, especially since you were so pleased with it that you had them build another house for you instead of choosing a different builder. It would be a shame if you had to recommend someone else to your friends since their quality seems to be declining...
    – FreeMan
    Commented Jul 6, 2020 at 15:39
  • Thank you FreeMan for your answer. I would certainly ask customer service to look at it again. It seems like the HVAC technician does not want to identify the problem because if they identity the problem they may have to replace the unit which would cost more to the company.
    – Krupal Patel
    Commented Jul 6, 2020 at 16:30

2 Answers 2

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A major part of the problem is the way the condenser is mounted. They are normally set on a concrete pad a few feet away from the house to facilitate air flow around the unit. Your condenser is mounted on steel brackets bolted into your foundation so the vibration, which every unit has, is transmitted right into your house. Check to see if there are any type of vibration mounts between the condenser and the brackets. Also check to make sure the foam or rubber pipe insulation completely covers the pipes.

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  • Thank you for your answer. There is a rubber pipe insulation but it still vibrates the living room floor. AC is mounted behind the living room. I don't mind little bit of humming but this humming noise I could clearly hear inside the living room which distract me everything AC is on. I don't know if this humming noise is normal or not. at night I could hear this noise from my bedroom which is on the second floor. would this noise be normal?? Thank you for your answer
    – Krupal Patel
    Commented Jul 6, 2020 at 14:56
  • @KrupalPatel Being bolted into your wall is causing a lot of vibration to be transmitted through the walls/slab. Condensers are noisy and it's attached right to your wall instead of on a ground mounted concrete slab. Have you checked with any of your neighbors to see if they have the same problem?
    – JACK
    Commented Jul 6, 2020 at 17:13
  • I have check with my neighbors. they have little bit of noise but not loud as mine. I was searching online and someone wrote all compressor are not same, even though it is from same manufacturer, some may be louder than other? is it true? sorry I don't know anything about compressor.
    – Krupal Patel
    Commented Jul 9, 2020 at 16:14
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I hear a harmonic to the compressor running this may be able to be dampened using isolation studs, this is a vibration isolation that has bolts sticking out of a solid rubber piece there is no metal to metal contact aprox 1/2” of rubber is between the bolts you remove the existing bolts put these in between the frame and the outside unit, one time I had to do this on a wall mounted the owner flipped out saying his refrigerant lines would now break until I opened the unit and showed him that the mount the compressor with vibration isolators. Other than this it is hard to tell if there are any other issues.

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  • "one time I had to do this" Is there anything you haven't done? :-) stay safe Ed.+
    – JACK
    Commented Jul 5, 2020 at 12:31
  • Thank you so much for your answer. it is greatly appreciated. in my previous house which I also bought from the same builder, brand new AC was not making such sound. I am just wondering if this humming noise is normal?? and what could be the definition of normal humming noise vs loud humming noise which is not normal? I am confused because the builder's HVAC technician came and checked it and said this humming noise is normal but I am not completely satisfied with it. please advise me on this humming noise if it is normal or not.
    – Krupal Patel
    Commented Jul 6, 2020 at 14:52
  • The mounting method really goes back to the type of system in my experience. I normally pad mount straight single speed compressors because there old time technology is a bit noisy, but with gell pads , neoprene isolators or other forms of isolation I have seen these compressors mounted on walls. When it comes to VFD or inverter driven compressors these are usually so quiet it doesn’t matter. A 2-1/2 ton unit on the factory rubber pads I can barely hear right outside my window with the window open.
    – Ed Beal
    Commented Jul 6, 2020 at 22:55
  • I have check with my neighbors. they have little bit of noise but not loud as mine. I was searching online and someone wrote all compressor are not same, even though it is from same manufacturer, some may be louder than other? is it true? sorry I don't know anything about compressor.
    – Krupal Patel
    Commented Jul 9, 2020 at 16:18

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