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Jon Danniken[_7_]

On 02/11/2013 06:02 PM, wrote:
On Feb 11, 4:25 pm, dpb wrote:

Think you'll need a lot more area than that to do any good...look at one
of these...

That's what I was thinking. A passive 2" square vent
doesn't sound very big. And with a flap of some kind,
etc, the effective area is further reduced.

My thoughts on a 2"x2" opening would involve increasing the size to
4"x4" (or even 6"x6") and installing a little computer fan into a frame
to fit. It would be trivial to built a thermostat to turn the fan on
with a thermister and a small signal transistor and a couple of
resistors, or you could go the lazy route and use a prebuilt electronic
thermostat.

You would, of course, need to supply a source of low-voltage to the cold
frame if you decided to go this route, but it would have the benefit of
being automated.

Jon