I have a Carrier (customers) Aquasnap 30RAP0156DAF00 (R-410A) and Digital Scroll Serial# 2310Q39728 that is in a process application with a 58 degree F set point for fluid cooling
It is faulting off on a T126 Alert code active. This is Circuit A High Discharge Pressure (650 psi). It is a shutdown that occurs after three automatic resets
The unit readings were with a 81 degree F outdoor ambient and a 66 to 67 degree return liquid temp.
As the unit lines out when it loads, the discharge pressure was 410 PSIG
Suction was 170 PSIG + or – 5psig until the scroll unloads
16-17 degrees SH
19-20 degrees sub-cooling
TXV at 100%
No temperature delta across the liquid line filter taken with a 2 channel thermometer with line clamp sensors (calibrated to each other)

When it loads the compressor the discharge pressure was spiking to 520+ PSIG

Afternoon temperatures have been hitting triple digits and that is when it faults out

All the obvious, plugged condenser, set so it re-breaths its own hot discharge (not the case), condenser fan speed (one fan) are OK

The loop has about a 30% concentration of glycol to water.

The system was helped a little when I adjusted the MAX T on the scroll solenoid from the factory default of 7 seconds to 6 seconds. The head pressure doesn’t spike so bed when it re-loads
I’ve got another like model (it is a 50 ton) so it has multiple compressors/circuit so (I don’t know if this counts) that doesn’t spike when it re-loads.

Anybody have any thoughts ?