Vacuum instructions for refrigeration rack system

[frigustek2013]

Good morning to everyone. I work in the refrigeration section of a frozen food distribution company, and have been assigned to assist the team of technicians sent by the factory for the start up of a large Hussmann low temperature R-404 rack refrigeration system, equipped with Copeland Discus compressors. I am trying to get as much informed as possible regarding the correct start-up procedures, and browsing through the factory manual, I just read something that I cannot clearly undestand. One of the first instructions reads as follows: "Isolate. Compressors. Frontseat service valves on suction and discharge. Close oil supply line immediately dowsntream of the Turba-shed." Then the instructions go through the evacuation procedures. When we reach the charging stage, it says: " Charging. Open. Compressors. Backseat service valves on suction and discharge. Open oil supply line immediately downstream of the Turba-shed." From this, I can understand that the compressors are not to be evacuated with the rest of the system, as they remain isolated while the vacuum is taking place. Does this mean that the compressors are to be evacuated independently. I will appreciate any comments. Thank you.

[macca33]

The compressor may have electronic pressure sensors which could be damaged with a low vaccuum. Maybe you can purge the comp or just pull a light vacc afterwards.

[Brian_UK]

Do you evacuation procedures include any pressure testing cycles?

[Rob White]

" Charging. Open. Compressors. Backseat service valves on suction and discharge. Open oil supply line immediately downstream of the Turba-shed." From this, I can understand that the compressors are not to be evacuated with the rest of the system, as they remain isolated while the vacuum is taking place. Does this mean that the compressors are to be evacuated independently. I will appreciate any comments. Thank you.

I imagine that is the factories operating procedure and not Copelands.
I have worked on many Copelands and never have I read any instruction
about "not" vaccing the compressor..

Also the method statement does not make sense??

If they are instructing you to open the compressors while the system is
vacced out, then as soon as the service valve is open the vac will be lost
and anything that is inside the compressor will be inside the system.

If they want you to charge the system with refrigerant before opening the
service valves, then whatever is inside the compressors becomes inside the system.

Both ways the system is compromised?

I know what I would do, but you need to be comfortable yourself. I would contact
Copeland direct and request the comp manuals. They are freely available.

http://www.emersonclimate.com/en-us/resources/faq/pages/copeland_compressor.aspx

http://www.emersonclimate.com/en-us/about_us/contact_us/Pages/Contact_Us.aspx


Regards
Rob

.

[FreezerGeezer]

That does sound odd. I don't recall isolating compressors when evacuating new systems, but it was a long, long time ago & back then I was just the gopher.

[THE DUDE]

The only thing that comes to my mind is if you are trying to pull/hold a deep vacuum 70-150 microns. If the compressors have oil in them you may Outgas the oil...that would be my guess.
Most newer Transducers can handle a deep vacuum. I believe you will be fine opening everything and Evacuating.

[nike123]

That is correct procedure since your pipes (and rest of system) could contain moisture which will eventually end in highly hygroscopic compressor oil. Only after you dried your piping, you can open compressor and vac shortly all together. Compressor is already dry. Maybe you did not read carefully all steps. Or it is missing in instructions, but you need final vacuum with open compressor to rest of system, but I will say again, only after rest of your system is dried and vac tested..

Also, if you have replaceable cores filter drier, evacuation should be done without cores and cores installed only at final evacuation when compressor is going to be opened.

[NewmanRef]

I agree with nike here. We always vacuum our system pipe work and cases/ evaporators with the pack shut off to rest of system. Separate vac pump on the pack. Both down to torr then open up for a short period prior to charging. I've always understood that it is to prevent comp oil being compromised by moisture in the system pipe work from installation. We also get the pump running on the pack prior to opening up compressors.