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View Full Version : R23 cascade unit Alista weather chamber problems







hvac01453
26-10-2016, 03:23 AM
This unit is 3 years old. It's a weather chamber. The high temp side is R404a with a Danfoss plate heat exchanger. The low temp side had a failed compressor burn out. Replaced it and cleanup driers twice so far., will do one last change. Tried to charge by weight 3.8kg but was unable to get even 1/2 that much in and the HL was tripping. 3 barr...I only recovered 1.3# of refrigerant. Pressure test over weekend showed no loss. I recovered again and put in 1.4# and it ran. This units diagram doesn't reflect what I see physically there. It has two circuits to the evapcoil. One is a TXV and the other a hand valve. It also has two either EPRs or CPRs which dump within 12" of the compressor suction line. DoesnT go thru the evaporate,...Each is preceded with an SOV. The markings indicate A7- 72psig. These two EPRs cut in at 10C and about 49C. At 10C the hand valve becomes the metering device as it climbs in temp and the TXV drops out, and adds in one or two of the EPRs as the machine approaches it's set point of 70C. After being at seventy C, When it is set to 50C, it takes over an hour to drop there, and the compressor freezes up with ice. Suction line is warm, I think the problem is in the setup of this hand wheel and the EPRs. How do I adjust these so that It will bring down the temp at about 2.5 degrees a minute or so. And not freeze up. How do I adjust the hand wheel and then how do I adjust the EPRs properly. What is there function. I have no sequence of operations. This company was South Korean and went belly up. Many times the compressor gets a block of ice on it on the temperature reset from 70-50C. Until it hits 49C two EPRs are functional (SOVs fired). At 48C , one SOV drops out, now run s on hand valve and one SOV down to 10C, at 9C the EPR SOV drops out, The hand valve SOV drops out, and the TXV SOV cuts in and runs on the TXV and has no problem once it's at a nine C set point it runs like a champ down to -50C.

All assistance is greatly appreciated...