A system for storing encrypted compressed data comprises a processor and a memory. The local logic solver includes a recording function and memory for retrieval of detected faults that are time-stamped and recorded locally to generate documentation and to track the elapsed time, starting when the degraded state of the device was detected and first signaled as a problem; other performance data is also recorded. The drive shaft has a longitudinal axis and resin bushes integrally mounted on the drive shaft for rotation therewith at positions along the longitudinal axis corresponding to vibration nodes of the drive shaft. A pair of engagement surfaces are spring biased against the cords to apply friction forces. The non-return valve and the expansion tank are formed as a single component and the non-return valve is located in an outlet port of the expansion tank.