I found an old thread referencing a 3 foot “window” around openings into the dwelling but this isn’t really the case for this problem. I was inspecting a home built in 1999 and found these problems relating to the location of the dryer vent to the A/C compressor. The back of the compressor was full of lint. The dryer damper was being blocked from opening by the conduit to the disconnect. The compressor was within 1-2 feet of the dryer exhaust. The inside dryer connection to the wall opening was that flexible silver Mylar. I referenced a 20’ rule of thumb in the report with a referral to a HVAC contractor for further evaluation. Who would have though this statement would have caused a boatload of grief!
In the mean time, I found this link that references 10’ but no hard and fast manufacturer recommendations. Anyone have more information that I may be missing?