Copeland ZRD-81 noise issue during modulation

[Partykus]

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

[monkey spanners]

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.

[frank]

when pressure LP and HP are the same

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?

[redroge]

compressor running the wrong way ?

[chemi-cool]

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

[mbc]

Hi
Most scrolls has this chek valve

[martinw58]

sounds like gas pulsing through a valve

[nike123]

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