One summer about 15 years ago I set up an array of hoffman boxes on tables out
in the sun. I had them all rigged with telemetry so I could log temps. I
tried fans, peltier coolers, heat exchangers, sun shields, insulation,
thermally activated vents and various colors. (That silver paint that the
railroad uses is lousy.)
Overall, the most dramatic lowering of temps was painting the box a bright
white.
There is a color called satellite white that was the best. Biege/tan was not
much better than the silver.
Then came sun shades and vent fans. About a tossup between those two. But
either one on their own was about half as effective as the bright white paint.
Thermally activated vents are pretty nice if you don’t want to use the juice to
run a fan. They have either an aneroid barometer type of cell full of ethanol
or a piston full of paraffin. Both expand when heated. They drive the
louvers. You can make your own piston if you can get the low temp paraffin.
Granger sells the louvers all ready to install.
Active cooling was dead last. Even with an insulated enclosure. Was hard for
it to remove any live load heating at all. Heat exchanger was not much better.
From: Sam Lambie
Sent: Wednesday, September 16, 2015 5:13 PM
To: af@afmug.com
Subject: Re: [AFMUG] Cooling an outdoor NEMA box?
Thanks for the tips guys.
Site is rebuilt now. Now to add exhaust fans. I like the idea of putting a heat
shield in front of the door. I might just go with that! Passive means nothing
fails.
On Wed, Sep 16, 2015 at 4:53 PM, Jason McKemie
<j.mcke...@veloxinetbroadband.com> wrote:
The "roof" of the fan cooled DDB boxes that I've gotten essentially do this,
with fans mounted on the inside of the enclosure at the top venting outwards
(under the solar shield) - seems to be fairly effective.
On Wed, Sep 16, 2015 at 12:26 PM, Brian Webster <i...@wirelessmapping.com>
wrote:
Don’t discount the idea of installing a flat plate on the sun facing face
with standoffs. Just having that absorb the sun and heat with the air gap
beneath does a lot towards not letting the heat build up inside the box. While
there will be some conduction it will be a lot less than the direct radiation
from the sun.
Thank You,
Brian Webster
www.wirelessmapping.com
www.Broadband-Mapping.com
From: Af [mailto:af-boun...@afmug.com] On Behalf Of Sam Lambie
Sent: Wednesday, September 16, 2015 12:48 PM
To: af@afmug.com
Subject: [AFMUG] Cooling an outdoor NEMA box?
I am in the process of rebuilding one of our sites from an old wooden box
to a more robust NEMA Wall mount cabinet that is 36x36x12.
Unfortunately, the cabinet is on the southern side of the building and I am
wondering how to cool the damn thing during the summertime heat.
I would like to install a 4 inch 100vac fan to suck air out with an intake
port on the other side. But it would be nice if the fans could be temperture
controlled. Has anyone done this? And what have you used to make it happen?
Sam
--
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Sam Lambie
Taosnet Wireless Tech.
575-758-7598 Office
www.Taosnet.com
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Sam Lambie
Taosnet Wireless Tech.
575-758-7598 Office
www.Taosnet.com
