Air conditioning units, methods of manufacturing, inventories, and buildings wherein certain heat exchanger modules are combined to make air conditioning units. In some embodiments, different combinations of different size modules are used to produce air conditioning units having different capacities wherein some identical modules are used in different size units. Various heat exchanger assemblies include spacers between modules, bends formed after modules are assembled into heat exchanger assemblies, attachment rails at the ends of the modules, inactive multi-tubes at the top and bottom of the modules, copper tubing between aluminum modules to facilitate field replacement of individual modules, name plates that attach between modules, attachment clips or spacers that snap attach to the modules, or a combination thereof, as examples.