The volume of air in the enclosure is irrelevant. What
you want to avoid is heat buildup in any part of the
controller. So if you flow enough air in and out
of the enclosure, the temperature in the enclosure
will be the same as the abient temperature outside the
enclosure. So air flow over the heat sink is important.
If there are vent holes in the controller for the rest of the
electronics, make sure air flows there also. Otherwise make sure
there is enough airflow around the whole controller to avoid
heat buildup inside the controller.

Wayne D.

On Sat, 25 Feb 2006 17:56:58 GMT, ~Roy~ wrote:

Well I have a box full of all kinds of muffin fans, some 120VAC and
others a mix of varous DC voltages, and installing a fan in a acrylic
enclosure would not incurr any additional $$, and can only be an
additional benefit since heat is a killer of electronics. I am just
thinking of how much space I need to allow around the enclosure I
make. I am sort of limited in space as to where it will be mounted,
and its certainly not the cleanest environment, so thats why I was
thinking adding a fan with filter for the internals in additon to
relying on the heatsink which will stick out the back of the
enclosure. I intend to make the lid sealed with a rubber gasket to
further keep chips etc out of it, so a typical electrical panel type
box would not be suitable. unless it wa a standard enclosure with no
knock outs etc that was designed to be totally water resistemnt.
My chassis is 2" high from the back plate, (not counting the heat sink
out the back as its not going to be included in the box) and measures
6.25" x 5.65" in size,. So do you think an enclosure with 1" space
all aroond the chassis itself would be ok? 8.25" x 7.65" x 3".
I am thinking of pulling air through the enclosures bottom through a
filter and directing the exhaust out and over the heat sink on the
back. Probably overkill but I want to ensure the controller has a
decent environement. Instalal insturctions are quite bland in mounting
it other than saying it needs to be in a place with no chance of dirt
and liquids getting on it........nothing in reagds to how much space
needs to be around it.