Angelantoni environmental test chamber

[exxu]

Hi all

I got a call for a environmental test chamber produced by Angelantoni.
It has a cascade refrigeration system with R404 in the high stage and R23 in the low stage. It seems that there a some leaks in the system.
My question is: does anybody know how much of each type of gas does the unit holds in normal conditions ?
The model is:WZT12-5060 D2 and it has one Dorin K3000CS compressors for each stage.

[exxu]

For normal operation (down to -60 C) the chamber needs 8Kg of R23 and 13 Kg of R404a.
Maybe you'll bump into this sometime.

[murray75]

I work on these every day. What you have to look out for especially with the R23 system is 'untraceable leaks'.
Normally Angelantoni chambers have a standing pressure on R23 of 11 Bar so if it has been on standby overnight you can check that pressure. I had one recently where the standing pressure was low, checked all over it with an electronic leak detector and found NOTHING!! I ran it and found that the R23 bypass AND cooling solenoid valve leaked when the system had reached it's operating temperatures. I got a trace on both when they were respectively hot and cold but not when at ambient temp. The R404a systems don't tend to leak that much, it's usually always the R23. One thing I do is guard against 'micro-leaks' by going around all the shut-off valves and service valves and tightening down the packing nuts and caps. Always tighten the caps on R23 TEV caps too. Note that I say the chamber should be 'on standby' NOT off. If it is off then the crankcase heater will not have been on for the R404a compressor. Dorin compressors are very susceptable to serious damage if started when cold. I've been out to 3 this year where the cutomer has started it from COLD and all three had to have new compressors. Another way to check the R23 charge is to run the chamber at+80'C for an hour then set it for -40'C at maximum speed. The head pressure on R23 should be top out at 275psi roughly.