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thcri
02-03-2016, 11:28 PM
Has anyone ran into this. We have a bunch of racks out there using AZ50 that even at start up during low loads the the compressors will vibrate really bad.

This is in Low and Medium Temp Applications

Grizzly
03-03-2016, 07:03 AM
Hi thcri
Just a wild guess without knowing your system.
But do you have something like a main non return valve in the discharge line of your system!

I don't know much about Digital Scrolls but historically we have eliminated a huge number of issues.
By fitting N.R.V's on the discharges lines of normal ones.
Alternately have monitored the system voltages?
Just random thoughts, but may assist?
Grizzly

chemi-cool
03-03-2016, 05:20 PM
Grizzly is absolutely right, if there more than one compressor in parallel, NRV must be used on each discharge line before the header.

http://www.danfoss.com/nr/rdonlyres/ddb0f71e-0348-4da5-a0b0-ab479b86c2a7/0/ga0451000gbpart2.pdf

Glenn Moore
03-03-2016, 08:56 PM
Hi
If it is just excessive vibration from the machine I would suspect the crankshaft counter balance weight may have moved or come loose which is causing the problem.
What Grizzly has mentioned about multi compressor installations is correct, where you would have to fit an NRV in each compressors discharge line before the discharge header, but most Scroll compressors have an inbuilt NRV in their discharge port to prevent the gas flow reversing the compressor when its power is removed. NRVs would make no difference if the compressor is vibrating when its running as it would be actually pumping gas out of its discharge and the NRV would be fully open. So if the shell is vibrating I would definitely suspect the counter weight, as I have experienced this problem several times. Its worth discussing this with your Copeland agent with the machines Serial nos.