"Doug" wrote in message
oups.com...
On Apr 26, 7:57 pm, lwhaley wrote:
On Apr 26, 6:50 pm, "Buck Turgidson" wrote:

Partially out of laziness, inertia, procrastination, and partially
because I
use it several times a month, I leave my Porter Cable air compressor
full.
Does this do longterm harm to the machine?

no

I've been led to believe that the compressed air will create moisture/
condensation in the unit which obviously can do damage. I usually try
to remember to bleed mine.

You are on the right track.
Actually the compressed air does not create the condensation. It is the
heat generated from compressing the humid air that causes the condensation.
Take a glass of ice water out into a hot humid place and you will get
condensation on the outside of the glass. Once a compressor has stopped
running and cools the condensation stops. The longer the compressor runs
and the more heat generated the greater the condensation.
Soooo, if you let the compressor cool and bleed off just the excess
condensation there should be no more water build up when the compressor sets
idle.
Typically however, no one remembers to return to the compressor to bleed the
condensation after the compressor has cooled. Bleeding is a good practice
and total bleeding insures that you don't have to stand around waiting for
all the water to blow out.
Typically also, the faster and fewer times a compressor cycles the less
build up of condensation you will get regardless of the volume being
compressed.
If you fill an empty tank form a cool compressor tank that is not running,
there will be no condensation generated.