Guess why this scroll compressor made this noise when I shut it off.

[vac-dude]

I like that sound. It makes the shutdown sound more dramatic

[rcinfla]

Newer scroll compressors have a discharge port check valve just behind the discharge port. This was added because of customer complaints of back wash shutdown noise. A lot of techs don't wrap a wet cloth or heat dampening putty around the ports when they braze in a new compressor and if the check valve receives too much heat it can warp it making it not close properly.

It is more important on high SEER units with large condensers that hold a larger refrigerant load. The subcooling level is a percentage of condenser volume that is liquid refrigerant. Larger condenser means more liquid refrigerant in condenser when it shuts off. Copeland specs specify a maximum system refrigerant load to avoid off cycle flood back due to larger refrigerant loads. Unit manufacturers get around this by closing down expansion valve and relying on compressor check valve to trap liquid in condenser during off cycle, preventing low side flood back through evaporator. On these units you will notice the high side pressure does not drop off after unit shuts off (unless it has a leaky check valve).

All scrolls have a floating differential pressure plate in the middle of top fixed scroll plate. It drops down during off state to unload compressor so when it starts up again it is not initially pushing against system high side pressure.

Copeland says their scroll compressor's don't need a short-cycle timer due to differential pressure plate, but there is another issue with a less than half second power glitch that can cause a scroll to immediately start to orbit backwards. It makes a terrible racket when orbiting backwards. Copeland says this does not damage scroll but it overheats compressors until it finally trips internal protection due to overheating. If you live in an area with a lot of thunderstorms and get a lot of power glitches you still should have a short-cycle timeout timer. The internal protection overtemp/overcurrent breaker has a limited number of trips before it gets damaged, requiring a compressor replacement.

I have noticed the turn off 'grunt' sometimes occurs more when it is cooler, like at night, with lower high side pressure. I am guessing lower pressure does not provide the 'slamming' force on check valve to completely seal it. It is a bit ironic because lower temps make it more likely to have flood back.

[williamtaylor]

We had a Carrier system installed 10 months ago. The ac unit has a Copeland scroll compressor. Started making this noise between winter and spring. Installer came out for a service, I was told this is normal and that all units make this noise. My concern is it didn't make noise for 4-5 months. He called Carrier tech support only to get confirmation that it's normal.

[seanmeier]

This is called ratcheting. It's the noise the scrolls make when they separate during shut down. It is normal for the system not to make this noise but slowly develop it and will not affect the performance or longevity of the equipment. Super common on any scroll compressor regardless of equipment manufacture.

[channelasianewterminatexii]

that sound like a pressure back i think the compressor pressure start to get weak.

[philltafolla]

Niceee video I had a system do the same thing after it was turned off, plus it made a whistling sound, kind of funny 😂 ... was a Payne 4 ton split..

[sdsd]

What can be done to fix said noise ? I have seen a lot of straight cool carrier's down hear in Florida made that sound when shutting down, Copeland compressor.

[Tails]

How did you fix it if you don’t mind me asking? Having this same exact issue with a 2019 arco. Pretty sure it has the lg compressor. Customer is complaining about it and I don’t blame him

[jimbofarrellgmail]

So this is expected to be normal with new scroll compressors? Lennox 4ton 410A AC (not heat pump) I installed 1 year ago and it did not make this noise. but now it does 1 yr later .
my customer is shittin. He's a perfectionist and retired, he doesn't want to hear this sound. can it be fixed? Is there something that can be done to eliminate this noise? TIA

[kinggenius]

the check valve very top in the center?

[Jets-and-airconditoning]

It shut off for 2 seconds and went on again or went into reverse

[nathang.]

the valve is fluttering... is that a straight cool? most of the straight cool scrolls make that noise.