Thanks for the thoughtful reply. This is a PS561 unit. I bought this unit and took it with me to Central America. What I have done is run about 120' total of stranded speaker wire in a loop back and forth under the roof panels and skylights so that cutting through the roof would place an "open" condition in the wire. I checked for "continuity" before making the loop complete to the window unit; I too, have ruled the motion sensors in this utility shed as unreliable because of the heat. The window units are; DS10A. I am currently in the States now for the Holidays and will return down there on the 6th of January. I will be in contact as it sounds like you have had some experience with these units!
Thanks,
Sam