Scroll Compressor Noise
The propaganda about scroll compressors says they are inherently quieter than piston compressors. However, as I walk around my neighborhood, there is a noticeable and annoying hum/buzz from all the scroll compressors regardless of brand. Way more noticeable than the older piston units. I hear a "waaaaaah" from the new units and only fan noise from the older squatty units.
I think my unit was quieter when it was first replaced, but perhaps I was so grateful for a cool house, I didn't care. It's not any louder than everyone else's. I measured the noise with a db meter at my unit, and it is at 72db. Not too loud. but at a very annoying frequency. Now that all my adjacent neighbors have new units, it's impossible to sit outside in the summer for all the noise. So what is normal scroll compressor noise? What sounds indicate a problem? Do we all have problems? Or is it just me being sensitive to the scroll compressor frequency?
May be that condenser fans have become slower and/or quieter, making the compressor noise more noticeable. Scrolls do have a different sound though.
Good point! The older fans make a kind of white noise, not so different from wind through the trees.
Originally Posted by ar_hvac_man
So the scroll compressor noise similar to a gas powered leaf blower a block away is normal? Normal but annoying?
Originally Posted by jax1
Ummm never anything remotely like that. But they are a lower pitch sound which does carry and penetrate walls better than higher pitch sounds a piston unit seemed to make, expecially with older noisier, higher speed fans.
Whether or not the service covers are fasteend tight make a big difference too. A metal panel rattling will really amplify the noise. I know a lot of builder grade units that are quietest with a large cinder block on top of them (but no blocking airflow). Although sometimes 2 minutes with a nut driver tightening sheet meatal screws will quiet it up. I'm tempted to sneak over and tighten a few on my nighbors tired old Carrier units. Fortunatly they are nicely oversized so they don't run all that much.
I believe when the compressor is not loaded to near its Nominal Btuh Rating & is low on charge the noise will be a higher pitched whining noise; which may be less bothersome at a lower pitch when rightly charged with a full load on the Scroll compressor.
Low charge plus underloaded due to low indoor airflow, etc., seems to me, results in the highest pitched whining Scroll compressor sounds.
Fully charged & loaded Scrolls seems to lower the pitch of their sound.
I would hope Techs would let us know whether they notice a little difference in those respects.
Last edited by udarrell; 07-16-2012 at 12:30 PM.
Reason: higher pitched whining noise...
I have noticed the scrolls do get a bit quieter as you get the charge dead on. I'm not the best judge though as I am getting somewhat hard of hearing.
In my work at Carrier we put the units in an anechoic chamber and measured the sound in decibels as well as sones with special microphones. We usually did this at 3 AM when there were no airplanes and motor traffic around the factory and the all the production machines were turned off The data is published.
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