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cfadm
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Cooling Grex
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Jul 28 10:17 UTC 1995 |
This is a corrected version of Rane's entry on cooling Grex (corrected
according to his instructions - I've also changed "west" to "east"
in several places, on the assumption that he was *consistently*
disoriented). I've frozen the original one and will let Rane kill it.
If he prefers, however, we can thaw the original and kill this one.
Other than these changes, this is the text of
Item 77 on Thu, Jul 27, 1995 (23:01) by Rane Curl (rcurl)
------------------------------------------------------------------------
On the evening of Thursday, 27 July, the basement of the House of Grex
was at 80 F, while the Inner-Sanctum of Grex was at 95 F (the door to
the room had been open for a little while at the time).
Grex itself uses some 850 watts. Its intake air was 96 F and its exhaust
air was 110 F. The unit is force-air cooled, taking in air by the upper
louvres, and exhausting the hot air by the power louvres. At the time
there was some recirculation of the hot exhaust air to the inlet because
the side of grex with the air vents was close to the side of a desk.
Other equipment in the room (modems, gryps, monitors, SCSI drive) use
about 500 watts.
How to cool the room - for both the sake of the equipment and persons
working there? I suggest the following:
(Please consult the picture of the room in the 26 July Ann Arbor News: the
east wall of the room is to the right behind Valerie; and the end of the
room where you see the Steves is the north wall.)
Outside air could be brought into the room via the basement window on the
east wall at the south end of the basement. Room air could be exhausted to
the *space* between the room and the east stone wall, and gathered into a
plenum for exhaust to the outside through the window in the east wall at
the north end of the basement. At least six inch ducts should be used,
with a good blower. Forced air circulation may be sufficient but, if not,
an A/C could be installed in the room with its condenser coils cooled by
the forced air circulation (this would add some electricity costs in
warm weather, but would also reduce the admission of dust to the room).
This would require permission from the owners for taking up half of each
of two basement windows for the installation of ducts. The system would
have the advantages to the owners of a) keeping the east basement wall
behind the east wall of the Grex Inner-Sanctum drier and b) the system
could have duct valves so that Grex heats the basement in winter, reducing
the owners' heating bills.
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| 96 responses total. |
davel
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response 1 of 96:
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Jul 28 10:22 UTC 1995 |
(I logged in as cfadm to freeze item 77 and then entered this. If I
have something wrong, I hope Rane will email me.)
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adbarr
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response 2 of 96:
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Jul 28 12:00 UTC 1995 |
rane, seems to me I have seen a/c's based on a split system design,
part outside, part inside connected with relatively small (1" ?) pipes
and not requiring a large window or wall opening -- would this be
an alternative?
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gregc
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response 3 of 96:
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Jul 28 12:34 UTC 1995 |
That's referred to as a split-ductless system. Yes, it would work here,
however those systems *start* at over $1000.
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n8nxf
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response 4 of 96:
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Jul 28 12:55 UTC 1995 |
Intake on top and exhaust on the bottom? Weird. I'd have tried it the
other way around. What is the temp. diferential between the floor and
ceiling? How about drawing cool air at floor level and ehausting out-
side? Makeup air could be provided through filter material installed
in an open window. What kids of volume of air does Grex expire?
An old window AC unit could also be modified to be a split system with
tourch, vacuum pump, etc. (I've done it.) or simply placed outside with
ducting coming in for the cold side or placed inside with ducting for the
hot side out.
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zook
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response 5 of 96:
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Jul 29 01:16 UTC 1995 |
(I guess the old item isn't frozen. I just added a response to it.)
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rcurl
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response 6 of 96:
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Jul 29 04:24 UTC 1995 |
I thawed 77 and wrote davel saying it was OK, since I had corrected
my error in the first response, but I must have done that just as davel was
entering this item. Since I saw 77 first now, and didn't know about 78,
I responded to zook's response there. Somehow we need to get these
two items to converge... cfadm?
There was no noticeable differential between the floor and the ceiling.
When I arrived STeve had put a fan inside the room to circulate the air.
I moved the fan to blow out the door, and the room temperature dropped
five degrees (one could feel the cooler air coming in at head level).
I think Klaus should have a look. In my opinion, a cooling system
has to be rather flexible, as what is needed in summer and in winter
are different. The room has to be ventilated in winter too, but
would probably not require any A/C. Also, from where it is desirable
to draw new air, or condenser-cooling air, and where the warm air,
from the room or the A/C, should be exhausted, will change with the
season.
The current 3 inch exaust pipe, and fan, are just inadequate. Even
if a larger exhaust duct could be installed, it would not be desirable
to exhaust the warm air from the machine room to outside directly,
in winter, as that would draw cold air into the basement.
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sidhe
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response 7 of 96:
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Jul 29 19:53 UTC 1995 |
Like I said, the ventilation modifications sound like a good
idea.
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zook
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response 8 of 96:
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Jul 29 20:37 UTC 1995 |
Don't forget about the humidity. Both too high and too low can lead to
problems. Anyone know the equipment tolerances for heat and humidity?
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rcurl
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response 9 of 96:
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Jul 29 20:57 UTC 1995 |
To solve the two-item problem, I have (again) frozen #77. There
were only a couple of responses there, so I have copied them, and
will paste them here, viz:
#2 of 4: by Bret Weintraub (zook) on Fri, Jul 28, 1995 (21:14):
That's a lot of watts! If you do the vent thing, what about the winter
time? The most efficient thing (it seems) would be a large-capacity fan
exhausted to the outside. I guess then that makes a dust problem, so you
would have to look at an air filter. Also depends on outside temperature.
What is the permissible operating temperature range for the equipment?
And humidity range?
#3 of 4: by Rane Curl (rcurl) on Fri, Jul 28, 1995 (23:30):
In winter one would close the valve on the inlet pipe, and transfer the
exhaust to the basement, which would heat it. The system I described is
about as close to a "large-capacity fan exhausted to the outside" as can
be fitted into the building configuration. However it also has more
flexibility. A filter on air drawn into the room would not be a bad idea.
With the A/C, however, outside air would only go through the A/C
condenser, and there would be much less air drawn into the machine room.
#4 of 4: by Christopher A. Cloyd (sidhe) on Sat, Jul 29, 1995 (15:52):
Sounds like a good idea.
We'll kill #77 soon. Its all here now.
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rcurl
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response 10 of 96:
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Jul 29 21:05 UTC 1995 |
I have done a calculation on the vent fan that was installed in the
machine room. I do not know what the venting velocity is, but
estimated it to be between 3 and 5 feet per second (a measurement of
this would allow the calculation to be improved). The vent pipe is
3 inches in diameter. Assuming 1400 watts dissipation in the room,
if the room were otherwise perfectly isolated, the exhaust air
would be between 240 and 140 degree F hotter than the inlet air. This
is not the case, so a lot of the room heat must be lost by transfer
through the room walls to the basement. It also means that the current
vent blower adds almost negligible cooling to the room. We might as
well just add a blower to exhaust the hot air to the basement, at least
until we can provide a more complex cooling system, since 90%+ of the
heat is going to the basement now anyway.
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mdw
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response 11 of 96:
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Jul 30 07:10 UTC 1995 |
Humidity is not a problem. Basically, humidity is only a problem if
it's condensing; and that can only happen if very moist warm air comes
in contact with cooler surfaces - as the air is cooled, it can no longer
hold all the moisture, and the excess comes out. In our case, we would
have cool moist air contacting nice warm equipment; the equipment would
warm the air and incidently reduce the humidity a smidgeon, and that
would be that. Indeed, for cooling purposes, humid air is actually an
advantage because it has a higher specific heat. Humid air is a
disadvantage to humans only because unlike computers we rely on
evaporative cooling. If we decide to store equipment instead of
operating it in the basement, humidity could be more of a concern, but
for running it, the only form of humidity that we really need worry
about, is the possibility of a flood.
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zook
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response 12 of 96:
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Jul 30 22:14 UTC 1995 |
Actually, I was worried more about low humidity (esp winter) and static
electricity.
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rcurl
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response 13 of 96:
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Jul 30 22:38 UTC 1995 |
There was a column in todays' (Sunday, 30 July) Ann Arbor News on "Air
conditioners can move", by James Dulley. He describes portable air
conditioners that have flexible ducts to connect the condenser section to
the outside via a window adapter. One version of this type of portable
conditioner uses evaporative cooling (with water) of the condenser, and
therefore exhausts moist air. This would reduce considerably the air flow
required on the condenser side, making it quite practical to use (say) 4
inch PVC pipe for the intake and exhaust ducts (as now used with
high-efficiency furnaces). James Dulley is the Ann Arbor News Utility
Writer (though I think he is syndicated, as he lives in Cincinnati), and
offers an "Update Bulletin No. 661" about portable A/Cs (one needs to send
$2 and a SAE). Should we? Or, do we have resident experts on line?
I checked with Big George, ABC Warehouse, and Fretter's, but none of them
carry portable A/Cs. One salemen said they are very expensive and very
inefficient. However, I think they deserve a look-see.
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mdw
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response 14 of 96:
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Jul 31 03:13 UTC 1995 |
Ah. Low humidity is not likely to be a problem in this basement.
It might be worth pricing A/C with actual separate condensers &
evaporators. It would be even easier to run a pair of freon lines
through the wall, and such systems are in fact in fairly wide-spread
use.
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n8nxf
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response 15 of 96:
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Jul 31 11:55 UTC 1995 |
The problem I see with separate condenser and evaporator is moving. Such
systems are difficult to move from one place to the other. A/C is also
expensive to run. Finding other ways to cool the equipment would be
more desirable I think. i.e. Draw the cooling air along the basement floor
under a sub-floor before feeding it to the machine. Said sub-floor should
be accessable for cleaning since it could be a high humidity environment
and mold, etc. would love it there. Exhaust hot air into the basement or
outside. Use it to heat living space in the winter or blow it in some
place that has a humidity problem in the summer. The earth's temp. 5 ft.
down is something like 55 F. Your in a basement, use it to your advantage!
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rcurl
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response 16 of 96:
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Jul 31 18:34 UTC 1995 |
1400 watts, 24 hours a day, will heat the basement even in winter. I
agree that that can be desirable in winter, as it will also save
fuel for heating the whole house, but the basement is already somewhat
tropic in the summer. In the summer, the heat has to be deposited
either outside or to the drain. I calculated the water requirement for
using water to cool the condenser of an A/C running at 5000 BTU/h and
it is $40/mo. However this would also require a special A/C condenser,
though perhaps not as complicated as the evaporative type mentioned
earlier.
The problem with drawing air from the basement is that that would have to
be replaced with air from the house and ultimately from outside, which on
hot humid days leads to condensation in the relatively cooler basement.
As to the "split-ductless" A/C suggested by Marcus - that starts
expensive, and doesn't it require a license to load and unload
refrigerants?
I think the least expensive option is installing intake and exhaust PVC
pipes to a window adapter, using a pretty powerful blower, and using also
a "cheap" window A/C with its condenser in a plenum. In winter, A/C would
not be needed and the room could be ventilated to the basement; in spring
and fall, the room could just be ventilated with fresh outside air, also
without the A/C; in summer, the A/C would be neded on hot days, with the
air circulation system cooling the A/C condenser.
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rcurl
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response 17 of 96:
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Jul 31 18:38 UTC 1995 |
I would like to suggest that item 77 now be killed, as 78 has taken
over cooling grex (if only it were that simple....).
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sidhe
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response 18 of 96:
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Jul 31 22:19 UTC 1995 |
Indeed.
The least expensive option, to me, at least, sounds like the
best one. But, alas, in this I have no expertise..
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zook
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response 19 of 96:
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Aug 1 02:04 UTC 1995 |
I think I like it, too. One point, though. Who controls shifting around
the apparatus with the variation in season? That would require someone's
physical presence in the dungeon. I would think that fall/spring
temperature variations might necessitate inconveniently frequent trips.
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rcurl
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response 20 of 96:
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Aug 1 07:33 UTC 1995 |
There are several staff members that spend more time than they would
like in the dungeon. Maybe some day it will just hum along on its own
for weeks....but don't hold your breath. Given how it has been running
since we moved there - from normal to stifling temperatures - I think
one can just transfer the operation on some suitable date. The
ventilation will in general be no problem; use of the A/C would be
temperature controlled, so it would not overdo itself.
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n8nxf
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response 21 of 96:
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Aug 1 12:39 UTC 1995 |
I've never been to the dungeon, however it seems to be in an "established"
building. One that's far from air-tight. It would be my guess that the
makeup air issue is not a problem and would hardly be noticed. (Gas fired
furnaces and hot water heaters as well as vented dryers also expell a lot of
air.) 4" PCV sounds good to me. Scrounge around and you may be able to
come up with a motor driven diverter that can be tied to a couple thermostats
to control cooling ;-)
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rcurl
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response 22 of 96:
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Aug 1 22:20 UTC 1995 |
You are probably right on make-up air. There are two central heating
furnaces in the basement, as well as a water heater and a vented drier.
Does anyone have a 5000+ BTU window air conditioner to volunteer for the
cause? Having on on hand would expedite thinking about its installation, I
would think, though, just putting in a potent exhaust duct and blower would
be a good start. I gave above an estimate of the room temperature rise
expected for two exhaust rates. If the exaust pipe were increased to 4
inches (PVC), and the exhaust velocity to 20 fps, the room temperature
rise with no other transfer of heat from the room would be 20 F - actually
about what was observed when I visited. That means that that ventilation
rate will be about equal to the other means of heat loss, so the
temperature rise would be only 10 F. That is still significant, of course,
when the basement is at 80 F. There would still be a role of an A/C.
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scg
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response 23 of 96:
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Aug 2 04:31 UTC 1995 |
We need to keep in mind that putting a hole in the outside wall for
ventilation is not an easy task. There are also no windows in the Dungeon,
if I remember correctly. Exhausting an air conditioner might be difficult.
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rcurl
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response 24 of 96:
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Aug 2 08:12 UTC 1995 |
I described in #0 the two windows that could be used for a vent
adapter: they are in the east wall of the basement, one just north
and the other just south, of the dungeon. There are no windows in
the dungeon per-se, but it would not be difficult to run the PVC pipe
to either window (if we were allowed). I would propose to install the
A/C with its "outside" side in a box in the dungeon, which is ventilated
with a blower.
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