DrewE wrote:
The part of the air conditioner on the roof is (or at least should be) separated from the ductwork side by a solid barrier, of course with some wires and tubes going through it. Outside air and inside air do not mix by design. If you think the source might be the air conditioner itself, it would be better to remove the inside cover/louver on the air conditioner unit and examine things from the inside. (There's no ducting as such on the outside side part of the air conditioner, just the shroud over the condenser, its fan, and the other external bits.)
Unless the powder is appearing from that air conditioner unit itself, I'd tend to suspect a source near where the pile is forming instead; but there's certainly no problem with taking a look at everything. If nothing else, it's well worth looking at the outside part of the air conditioner and cleaning out dirt or debris if needed to keep it working efficiently and effectively.
Bingo. There is NOTHING in a RV rooftop AC unit that will produce debris or dust. What DOES produce this dust is, at EACH roof AC you need to make sure there is NO possible way the cavity of the roof between to top and the interior ceiling has open egress areas. If so, the AC unit will "pull" air and debris from this cavity as long as from the inside of the RV. The cavity will be behind the AC filter's, hence the fine debris. This is where AC Foil Tape comes in very handy to seal off those areas. If your AC units have the inside Plenum mount, you remove this mount and you will see the gaps on the 14 inch square roof cut out. SEAL those gaps and your problem goes away. IF top mounted AC you will have to remove the unit from the roof and do the same thing. Doug
