Reguardless of where i was taking my temps, on a 73 degree day, you shouldnt have to go any further than the return and any supply to take your measurements. The attic shouldn't be exceedly hot to cause heat penitration problems but you could have a hole in the return ductwork big enough to causea lower delta t. You do need to make an effort to examine the the a/h panels and return plenum.
Originally posted by hotsummer101
appltech1, you mentioned that I should be easily getting 19-20 Delat T, but since I can only measure at return filter (Ceiling) and nearest register how offset will my measurements be ? as opposed to measuring at the air handler.