Disclosed embodiments include HVAC systems, and power machines incorporating the same, which utilize an improved exchanger configuration in which the two separate heating and cooling exchangers of conventional systems are replaced with one composite exchanger. The composite heating and cooling exchanger includes nested heating and cooling tubes. The configuration of the tubes can be used to improve conductive efficiency in transferring heat energy to conductive fins, as well as to improve convective efficiency by increasing dwell time of air passing through the exchanger. The disclosed composite exchanger allows for a reduction in the overall exchanger package size package used in an HVAC unit.