A method is disclosed for assembling a flattened tube multiple tube bank heat exchanger that includes a first tube bank and a second tube bank, each bank including a plurality tube segments extending longitudinally in spaced parallel relationship. A spacer clip is installed on a longitudinally extending edge of each heat exchange tube segment arrayed in a first layer of tube segments. A plurality of heat exchange tube segments are arrayed in a second layer in engagement with the spacer clips installed on the tube segments of the first layer.