Hi all -
New guy here. I have a really irritating issue I need help solving.
I work at a small hospital, and our CT scanner uses a KKT/Kraus industrial cooler. Nine months out of the year, it runs fine, but when the ambient temperature drops below 20*F we begin having trouble.
This unit is a Type KPC 108-L-U/S. It uses a 7.5 ton (i think) Copeland scroll compressor. The unit is charged with 15 lbs. of R-134a. The refrigeration unit cools down a 38% ethylene glycol/62% water mixture which is pumped to yet another heat exchanger, which cools down distilled water that cools the gantry of the CT unit. The unit is designed to cool the glycol/H2O mixture to a temperature of 6.5-11.0*C.
The unit is designed to place an "artificial load" on the refrigeration system (via hot gas bypass) at the times when the CT unit is idle. This should allow the unit to run continously. However, when the ambient temperature is around 20*F or below, and there is no heat load generated by the CT scanner, the unit shuts down. Somehow, it always seems to happen at 2 A.M. when there is a wind chill of -20.
The techs from Kraus and Siemens have checked and claim that his is the only unit that ever had this issue, but they cannot find a solution to the problem. We need this chiller to run 100% of the time, since we may need the CT for an emergency anytime.
Our refrigeration expert wants to run a frostex tape on the gas line to keep the pressure high enough to prevent shutdown. I think we should find a way to heat the glycol/water mix to around 11-12*C when the CT is idle to prvide an actual load on the system.
Has anyone else ever encountered a system like this? My boss doesn't want us to modify it too much since it is such a critical piece of hardware, but I'm getting tired of getting called in on Saturday nights...