Copeland ZRD-81 noise issue during modulation

Hi,
I have a problem with compressor ZRD81. AC unit is equipped with one compressor and during PWM modulation, when pressure LP and HP are almost same - appears strange noise (check link below):

https://drive.google.com/file/d/18Nh...ew?usp=sharing

Any ideas what is going on?

Thanks

Can't get the audio to work, maybe there is not enough pressure differential to hold the scrolls together as designed at low load. The digital scrolls (not sure if that what you have) do growl a bit when unloading and loading.

Quote:

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Originally Posted by Partykus

when pressure LP and HP are the same

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When the system is off and pressures are equalised then this statement could be true but I struggle to imagine a running system with equal pressures?

compressor running the wrong way ?

Some times just before pressure equalized, scroll is turning backwards .
To avoid it' a NRV should be installed on the discharge line.

Hi
Most scrolls has this chek valve

sounds like gas pulsing through a valve

Probably mechanically damaged compressor!
Check this thread on another forum:
https://hvac-talk.com/vbb/showthread.php?2194688-Copeland-scroll-rattling-noise-every-10-15-seconds