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Jfb
03-03-2011, 03:43 AM
Hi everyone, i am Beginner on rack system and i would like to know, what is the fasted procedure to pump a big 8 fans condenser without split, if i have a leak

And i would like to know if the procedure is different on a cold or warm day

Please no answer like remove the acces valve!!

Tesla
03-03-2011, 06:09 AM
Hi Jfb
It's been many years since I have worked on a rack so if I'm wrong or there is a better method someone will correct me. Basically like any system override the controls and pump the system down by closing down receiver valve and forcing compressor/s on with cond fans manualled on and EPRs open. Once pumped down where suction is just above positive pressure isolate compressors - usually requires repeating this procedure (wait for 15 minutes each time). then fill large cylinder/s from the liquid line. Hook up reclaim unit with large bottle/s and reclaim gas from the condenser. At this stage depending on how fast and reliability of valve tightness you may use nitrogen or may not (I wouldn't due to possible contamination). Fix the leak and leak test then evacuate condenser. Depending on valve tightness will depend on how much of a vacuum you will get. Then refill the reclaimed gas into condenser and repeat leak test just to be sure. If all good open valves slowly (receiver first) then set system back to normal control. You may need a little more refrigerant. I could point out a few short cuts but considering you don't have experience I think it will complicate the procedure. This would be best done at night time to cabnet temps getting too high. Is it low or medium temp product? If low temp the stock should be removed and place into freezer room/s. Curtains if fitted should be closed and evap fans switched off during operation. Should be done with two techs just incase something goes wrong and for a safety factor. You may be able to slightly over cool cabnet temps prior to operation and there may be EEVs to open with the controls system for the pump down.
Members please feel free to correct, improve or critisise this procedure.
You may get away with just isolating the high side from discharge valves to receiver outlet and recover liquid first from receiver outlet then gas, this just depends on what isolation valves there are and access points to fit hoses.
Other points are to ensure low side is not over pressurized (if too much liquid is there and temp rises too much) and ensure all safety precautions are taken like monitoring hi and lo side pressures during operation. This will depend on how big and how complex the system is. It could be real simple or there could be complex with some unknown/understood components in the system.
On the short cut I would override the controls and pump out refrigerant with compressors from the liquid line then equalize high and lo sides, isolate condenser, reclaim condenser, fix leak/s, leaktest, evacuate cond, open valves, refill refrigerant into condenser first then, charge the rest, switch to auto control wait for system to settle, then top up, come back 4 hours later and recheck system. But there are a lot of different systems out there - lo, hi, compound, cascade etc.

Jfb
03-03-2011, 01:38 PM
Thx for the answer tesla but in closing the king valve, i think too much liquid will trapp in the condenser its too long to recover after. I already heard that i need too close the ball valve on the drop leg and raise the pressure too 300 psi and close comp and discharge and after open the dropleg so with pressure difference the liquid will drop in the receiver and it will rest only vapour but im not if i forget something

Jfb
03-03-2011, 02:07 PM
I say that im a beginer . I never works on compound rack and other technologie but im not a rookie in refrigeration . I works onsystem like high speed defrost , enviroguard , compound compresseur... So dont be affraid to give a More technical method thx

Tesla
03-03-2011, 11:53 PM
OK Jfb
Using reclaim units is very slow so what I try to do is use the compressor/s on the unit as much as possible to do the work for me eg. I've seen some fridgies reclaim the entire charge from a chiller where I would pump it down and just take the liquid out of the liquid line then reclaim the left vapor. If there are two chillers and they are both short of gas I would pump the (most of) charge from one into the other. Also your low side can hold some (small) of the charge.
Another thing with reclaiming lots of refrigerant is the reclaim bottles get hot and the pressure goes up so I either cool the bottles or the liquid going into the bottles and sometimes it's a lot faster to use say 3 bottles when you could fit all of the charge into one bottle if it's just going back into the same system.
But I do stress you must be very careful to not over pressurize the low side or over fill anything - each system is different and different methods are used it depends on where you can get at the system with existing valves and fittings. If you can fit them you can use more than one reclaim unit. I hope this helps a little.

oldtimer
14-03-2011, 07:50 PM
i would run the pak at 280 psi for ten minutes so any liquid is pushed out of the condenser turn pak off isolate it and decant . use another pak if you can ;)