Tracy R Reed wrote:
I think I might go down to the
hardware store tomorrow and buy some of that flexible plastic dryer vent
hose to attach to the computer and then hang out the window. But how to
attach it to the back of the case? Hmm...just had an idea: I could get
one of those metal fittings that go on the inside of the wall that the
dryer hose attaches to, drill four holes in it, and put the bolts that
hold the fan in place through it and then through the case and the fan.
Yep, a run to the hardware store is definitely in order. I'll let you
know how it goes.
Please, take pictures. This I *have* to see. :)
An ingenious idea, really. One thing you might want to consider is that
adding ducting increases backpressure. You might want to add a 120 mm
fan on the output side to help the air along. You should also consider
filtering the input air into the computer. It'll fill up with dust fast.
But that's regardless if you duct to the outside or not :)
As far as current meters go, if you don't want to put something inline
you're stuck with the "amp clamp." However, this requires you to strip
the insulation back off a power cable and clamp the device around just
the hot (black/brown) lead -- that will tell you how much power is going
in. For posterity purposes, you should also check the neutral
(white/blue) line and make sure the current in on hot is the same as the
current going out on neutral. If it's different, clamp it around the
ground (green/yellow). If you have current sinking to ground that's an
indication of a serious electrical condition in one of your pieces of
equipment. But I digress! Really, the best way to measure this is with
an inline device. Once upon a time I bought a few analog panel-mount
ammeters at the local electronics store, bought a 2U quarter-depth rack
chassis, cut some holes in the front and back, then mounted the meters.
I had a NEMA L14-20P on the input side, and a pair of NEMA L5-20R on the
output side, which fed a couple PDUs. This, at a glance, would tell me
how much current I was draining on either leg of the 240, and how
balanced the load was (perfectly balanced 240 should have 0A drained
from either leg to neutral). It ended up being a really sexy project. I
wish I still had that device. I still have the schematics if you're
interested.
The heat thing you described is just about dead-on. Energy is never
wasted, so all the power dissipated by the machine goes out as either
heat or light. Since the amount of power it takes to create light is
negligible (*) we can safely say that all the power coming in is
dissipated as heat. Thus, for each amp drained, each 120W dissipated,
you're generating 409.68 BTU/hr of heat. Most modern computer systems
dissipate between 200 and 400W of power dependent on configuration and
usage. So, for each computer assume you're generating 1024.2 BTU/hr
(that's a median 300W load). Also keep in mind that things like routers,
switches, cable modems, monitors, etc. also dissipate power as heat and
their usage must also be taken into account. Your typical 20" CRT
dissipates between 120 and 145W of heat. Your typical DFP dissipates
35W. Add the aggregate power consumption (W) of your devices together,
multiply by 3.414, and you get BTU/hr. In a residential setting you want
to size your air conditioner grossly above that number for a couple
reasons: a) when it's running you're paying dearly for it so you don't
want it running all the time b) larger units are more power-efficient c)
you want the unit to still be able to cool the room when you're in it or
in the case you leave the door open. To put this in perspective, the
typical room AC you can get for $100 at home depot will cool the room
5000 BTU/hr. Also, as air conditioning has the wonderful property of
drying out the air, you might want to consider an evaporative humidifier
(with automatic hygrometer) to keep the humidity at a constant 35% to
prevent the buildup of static electricity. Static bad. The humidifier
will also assist in cooling (you get the "swamp cooler" effect).
(*) in the case of incandescent light bulbs, 99.999% of the energy used
is dissipated as heat. Fluorescent lights are much more efficient, as
only 99.99% of their energy is dissipated as heat. :)
Hope your project goes well.
-Kelsey
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