Solenoid Valves in Parallel Compressors Rack System

[NoNickName]

NoNickName, I didn't understand the last part about prevent hammering stopping pump down. Since I'm talking about a Parallel Compressors Rack for several rooms.

Yes, this is typical compressor pack / multiplex system. When the last of compressors stop, it is a common practice to stop it on a low pressure switch. This is referred as pump down procedure. At restart, when the SV opens, refrigerant fills up the vacuum created by the pump down, and the result is liquid hammering.

Can you tell me more about what would be a "New age" control solution for this kind of systems? Where can I find info?

Register yourself and download the programmable controllers brochure form www.dixell.it . You can have a slight glance of the new ideas for the refrigeration sector

[georgedvf]

Yes, this is typical compressor pack / multiplex system. When the last of compressors stop, it is a common practice to stop it on a low pressure switch. This is referred as pump down procedure. At restart, when the SV opens, refrigerant fills up the vacuum created by the pump down, and the result is liquid hammering.

Ok, but when there's several rooms and only one room stops it's the same hammering and no compressor stops, so no pump down is happening there, right? I think the only solution for this is to install the SV near the TEV...

Register yourself and download the programmable controllers brochure form www.dixell.it . You can have a slight glance of the new ideas for the refrigeration sector

Thanks for that link, I will look into it.

[georgedvf]

Just to get it right, so when using Parallel Compressors Rack and several rooms yo DO use SV neear as possible from the TEV to stop refrigeratn flow when set temperature is reached or defrost is required, right??

[NoNickName]

Just to get it right, so when using Parallel Compressors Rack and several rooms yo DO use SV neear as possible from the TEV to stop refrigeratn flow when set temperature is reached or defrost is required, right??

That's the general idea. Your mileage may vary.

[Peter_1]

...At restart, when the SV opens, refrigerant fills up the vacuum created by the pump down, and the result is liquid hammering.....

Not if teh SV is mounted just in front of the TEV.
Carrefour , Colruyt and Delhaize, big Belgium supermarkets describe in their manuals you have to install the SV's as close as possible to the TEV.

[NoNickName]

Not if teh SV is mounted just in front of the TEV.

It doesn't matter. It probably is worse when the SV is near the TEV. Same hammering in less volume.

[Peter_1]

It doesn't matter. It probably is worse when the SV is near the TEV. Same hammering in less volume.

I totally disagree with this statement, the closer the better, if installed besides each other no hammer effect at all what DP you anyhow may see across the valve.
I had a judicial case about this with a loss of goods of over 250.000 € due to the long distance between SV and TEV.
We did measurements in both cases and DP can go to 100 bar.
It's also mentioned very clearly in the recommendations of Danfoss.