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Appleton
24-03-2008, 08:17 PM
Hi everybody

I´m new into the forum, before anything excuse me by my bad english, my natural language is the Spanish, so I hope your understand.

I will try to explain my situation, I´m Aplication Engineer, In my company we bought a Rack of compressors in paralell (has 2 screw compressors) for a project with 8 systems of evaporators independents or Coils, like you call it, this Rack has a CPC controller, the problem in this Rack is when some systems gets into defrost (with 3 systems in defrost) the controller send the signal to close the solenoide valve of each system to get the defrost, but when this hapen the compressors gets alarm and send the signal at the controller, this show us in the screen the "Oil fail" so we check if the compressors doesn´t have oil, but the oil level in both compressors are good, so it is no the fail.

After the review the behaviour of the Rack we discovered when some systems gets into defrost, the discharge pressure toward the condenser increase at 300 psig, how we are working with R-404a so for this reason the presostato of each compressor get protect by high pressure, and this open the electrical circuit, and this allows the controller show us the alarm, however allways show the "Oil Fails" because all the posible amalarmas are in serie, which it is a bad practical by the manufacturer of the Rack. so I´m thinking that the problem with this Rack is in the receiver, I think is small, what do you think about this? Somebody have other perceptions about this?

And, Somebody know a method o formula to calculate the receiver for a refrigeration system?

Thanks for your coments in the future.

Brian_UK
24-03-2008, 11:45 PM
Hi Appleton and welcome to the forum.

This subject has been discussed in the past hereabouts and having searched the forum here are at least two threads on the matter you may care to read through.
http://www.refrigeration-engineer.com/forums/showthread.php?t=4365

http://www.refrigeration-engineer.com/forums/showthread.php?t=1174

jumanje13
25-03-2008, 07:55 PM
hi appelton
the system is new or work before and the defrost is hot gas or heater i think with some fool that the solenoid of hot gas isnt work you didnt say the system hp and volume at all we know that every engineer can solve his proplems
best regard appe

Appleton
17-04-2008, 03:42 AM
The Rack is New, We bought the Rack, and the Defrost is by out cicle, this work at 23ºF of SST , the capacity of the Rack is 110 HP and have a receiver of 16"x60" horizontal.