Jason Bleazard <dml@bleazard.net> wrote:
> jon@dakota-truck.net wrote:
>>
>> I'm in the process of designing an office for myself down in the
>> shop, and part of the office will be an air conditioned server closet.
>> I haven't worked out all the details yet, but I definitely plan to run
>> ductwork through the wall of the building so that I can shut off the
>> A/C unit during the winter; once the outside temp drops below 50-60 F
>> or so, the only cooling energy required would be a fan to move the air.
> This sounds like a potential PIC project. You'll need a couple of temp
> sensors to monitor the inside air, outside air and computer temps.
> Check against a desired setpoint, and decide whether to use outside air,
> how much to blend it with the inside air, or to switch on the A/C with a
> relay. That way, you won't have to constantly worry about it, and if we
> get a cool night during the summer it can automatically switch over to
> outside air.
Yep, I thought about that, but then that would require me
re-learning yet another skill which has fallen by the wayside. ;-)
Like I said, I haven't given it a great deal of thought yet, but what
I was thinking of doing was to use an air conditioner with a built-in
thermostat, and I would use a second thermostat to trigger the fan
that brings in the outside air. If I set the fan thermostat slightly
below the A/C thermostat, the A/C shouldn't kick on unless the fan
wasn't doing the job. With that system, I'd still need some way to
shut off the fan system when the A/C system was on, just so that the
fan wouldn'd be blowing the A/C air right back outside. Possibly an
outside air temp sensor would be required. Who knows, it probably
*will* end up being a PIC project... ;-)
One catch with using a PIC to control the whole thing would be
finding a way to have it switch the A/C on and off. A 120v relay
would probably work with an older style air conditioner, but not so
well with one of the newer style models with the digital controls and
such. (When the power is cycled on those they often have to be turned
back on by pressing a button and/or the thermostat setting goes back to some
predetermined temp.) Possibly I'll just get a newer style A/C system
with a built-in thermostat and have it "on" all the time, then use a
PIC or some other logic system to decide if the outside air fan should
be running or not. If I get lazy, that "logic system" might be to
simply mount another thermostat outside, wired to a relay which
provides power to the fan system.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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