This invention provides a thermal energy system comprising a heat exchanger for transferring thermal energy between a source and a load, the heat exchanger having a primary side associated with the source, and a secondary side for conducting a fluid associated with the load, wherein the secondary side of the heat exchanger is passively back-flushed upon consumption of a portion of the fluid. Other related embodiments are disclosed. The exercise device may also include optional kneefoot dollies and resistance bands. Upon insertion of the transceiver in the port, the device interrogates the transceiver to obtain specification information.