The attic solar pool heater can be mounted inside the attic, which is preferred. Or, it can be mounted external to an attic either embedded as a part of the roof structure or on a gable end. The above 1988 document shows these methods for the PCS1. The PCS2 and current production model PCS3 have the same option. Alternatively, the heat exchanger can be mounted on the floor of a garage attic and the air from the underside of the roof deck can be routed to the input of the heat exchanger at the fins. Download the PDF document to gain a better look at the notes on the drawing. Be sure to observe the caution bullet points such as keep the unit horizontal for proper operation of the internal lead detection float.