What makes this noise in an AC system?

16 years ago

My central AC makes a noise when running. The air handler and coil is in the attic above a bedroom and the lines go down inside the wall 2 floors to the outside unit. Best I could describe the noise is buzzing and gurgling combined. More of a buzzing if I had to choose one. It seems like it's inside the lines. Not sure if that's possible. That's why I'm posting here. It's not like I will fix it myself, but I want to know what to tell the tech when he comes out. Could it be a low charge or something like that?

I did go into the attic and check for loose stuff that could be vibrating but didn't find anything. I have two units and it's only one that is making the sound. I can't hear it at the unit because it's just too loud with the unit running, but down underneath in the bedroom, it can clearly be heard. Sounds like the corner of the room where the attic floor meets the bedroom wall. That is where the lines go across the attic floor and drop down into the wall to go down and eventually outside.

Is buzzing a normal occurance? I was hoping it was for an easy fix, such as a charging level issue. thanks

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Comments (3)

maryland_irisman
16 years ago
The gurgling and buzzing is normal and really exists in all units (i.e. it is likely you have nothing wrong but an irritating noise). I even listen for this noise when I first approach a unit because it gives me sign of it's "health" so to speak. There is an explanation and several solutions which use a lot of technical terms and even some elaborate devices which can be added to the system but, I won't go into all that right now. I'll explain as simply as I can and hope you understand (and also hope I explain it simple enough!!!)If the noise is noticable but not irritating or disturbing, I think the following is most likely the problem.

It is associated with the refrigerant as it cycles through the line sets. If the lines touch the structure anywhere along the hollow wall, the noise can be transmitted more noticeably. It may be that where the lines enters the attic space, they are affixted to a joist or just laying against it. If they are affixed without a vibration dampening means, the noise will be more pronounced. A rubber grommet inside a fastening clamp usually minimizes the noise. The air handling unit where the evaporator coil is mounted should also be dampenedor the gurgling and buzzing will be heard also. Although there is not much noise associated with it in the way of gurgling, there is a condensate drain to drain off the evaporator coil. The buzzing is usually associated with the refrigerant leaving the metering device and the gurgling is associated with the liquid refrigerant going up the line to the metering device and some can be heard as the refrigerant is in the evaporator coil. When the unit shuts off, you may hear this noise more clearly for 30 seconds or so.

I hope this helps you understand and if you should call a technician to remedy the problem, you'll have a better idea of what he'll be doing. Good luck and feel free to email me if you need more info!!
udarrell_2007
16 years ago
A gurgling, pulsating surging sound near the evaporator coil, when you press the small liquid line to your ear, can be an indication of non condensibles such as air in the refrigerant system, it cold also be an under charged system. Very low airflow through the coil might cause a TXV control to shut down the flow to the point of possibly causing a gurgling pulsating sound.

Let me know what you find!

Linked page, Click on Liquid Line Noise.
udarrell _ 2007

Here is a link that might be useful: udarrell.com
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dlrobinson01_bellsouth_net
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What causes your central unit to make a pulsating noise like the agitator in a washing machine?

What makes this noise in an AC system?

Comments (3)

maryland_irisman

udarrell_2007

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