Subcritical CO2 rack - random pressure spike problems

Hi, all.

First time poster on this site.

I have been scratching my head with the following and hoping anyone can suggest a solution i have not already tried.

I am working on a KIRBY SUB CRITICAL RACK SYSTEM - consists of 1x MT R134a system & 1x LT CO2 system.

MT cabinets/system all working well with no issues, all cases hitting temp and cycling.

LT system is having all sorts of problems with cases turning off randomly (sometimes all cases) when the discharge pressure of the CO2 spike to 495psi+ , i assume the turning off of the cases is a safety function of the system to reduce load.

There seems to be little to no trend when this spike happens nor does there seem to be any obvious reasons for it - I.E. no doors are opened and no cases are on defrost when the spike happens.

I have tested and calibrated ALL probes/transducers/bypass valves/check valves/heat exchanges/liq subcoolers/cascade system/ETC

The only variable is that the Heat exchange for the liquid line coming from the MT that goes into the CO2 cascade has been removed. If this was the problem i would expect to see an ongoing issue and not just a random spike.

ANY information or advise would be greatly appreciated!!

.

I have so many questions before I could even start..................... :)

Were there any problems with the C02 side before the liquid line heat exchanger was removed?

What was the ambient temp at the time of the C02 spike?

What temp and pressure was the R134a low side at the time of the C02 spike.

How long has the system run?

Has any C02 vented from the safeties?

That'l do to start with. :D

Rob

.

Not relevant

Does it trip on a mechanical HP or transducer?
Where abouts on the system is the switch/transducer?