AC doesn't work when it's _HOT_ outside!
reyn...@vu-vlsi.ee.vill.edu
air-conditioning.
I'm curious to know why my 12x12 room "isn't air-conditionable" (told to
me by customer service "professional"), at least not to my standards.
My idea of AC isn't something that reduces outside temperature by 20
degrees(F)-- coming into an 85deg. room after a day in 105+deg. sun isn't
exactly my idea of comfort. My idea of AC isn't something that works
worse as the temperature goes up-- it should be most effective on very
hot days, when I want the cold air most. My idea of a "temperature" dial
is not a thermostat(shuts the unit off at a certain temp)-- when I turn
the dial down, that means I want COLDER air coming out. My idea of AC
isn't something that blows out 65deg. air for hours and hours trying
unsuccesfully to cool a 120+deg. room.
Imagine if freezers worked the same way as window air-conditioners?
"Sorry, Mrs Jones... you can't expect your ice cream to be kept solid
when it's so hot outside. Buy a bigger freezer, maybe that will work."
That's essentially the line I'm getting from the service people. They
just don't seem to understand that I want my room kept coldest on these
hot days. They say that's not how a/c's work-- they don't necessarily
make a room cool, they only make it coolER than it is outside. Blah!
So, anyway... I have this new Carrier 6100 BTU window unit. I'd like it to
cool a 12x12 room TO MY LIKING. They say this unit will never do the job,
and no "fix" can be made to make it do so. Is this right? Can't they pump
it up with a different (colder) freon? And do something to the fan so it
shoots out more air?
Why is it that I can sit in the blazing sun with my car a/c on and have
it pump out 25deg. air, yet my window a/c that's in the shade dispenses air
that's nearly 3x as hot?
What do BTU's have to do with the price of apples? This new 6100 BTU a/c is
replacing a smaller 5000 BTU unit. Those 5000 BTU's would freeze people
out of the room, but now 6100 BTU's can't even keep the room comfortable.
What gives? Do BTU's refer to temperature, or just some air displacement?
Enough griping... Does anyone have any suggestions on what kind of a/c I
should buy? Commercial a/c's in stores freeze people out, why can't I get
the same perfromance from a smaller window unit?
Jim. (about to move to Alaska)
George Goble
>I'm a person who likes COLD things-- cold weather, cold beer, and COLD
>air-conditioning.
>
>I'm curious to know why my 12x12 room "isn't air-conditionable" (told to
>me by customer service "professional"), at least not to my standards.
>
>My idea of AC isn't something that reduces outside temperature by 20
>degrees(F)-- coming into an 85deg. room after a day in 105+deg. sun isn't
>exactly my idea of comfort. My idea of AC isn't something that works
>worse as the temperature goes up-- it should be most effective on very
>hot days, when I want the cold air most. My idea of a "temperature" dial
>is not a thermostat(shuts the unit off at a certain temp)-- when I turn
>the dial down, that means I want COLDER air coming out. My idea of AC
>isn't something that blows out 65deg. air for hours and hours trying
>unsuccesfully to cool a 120+deg. room.
>
>Imagine if freezers worked the same way as window air-conditioners?
>"Sorry, Mrs Jones... you can't expect your ice cream to be kept solid
>when it's so hot outside. Buy a bigger freezer, maybe that will work."
During the 120F Heat-index heatwave, many Lafayette, IN restaurents
had hot "cold" food, melted cottage cheese and icecream..
Kitchen temps were around 130F.
>
>That's essentially the line I'm getting from the service people. They
>just don't seem to understand that I want my room kept coldest on these
>hot days. They say that's not how a/c's work-- they don't necessarily
>make a room cool, they only make it coolER than it is outside. Blah!
>
>So, anyway... I have this new Carrier 6100 BTU window unit. I'd like it to
>cool a 12x12 room TO MY LIKING. They say this unit will never do the job,
>and no "fix" can be made to make it do so. Is this right? Can't they pump
>it up with a different (colder) freon? And do something to the fan so it
>shoots out more air?
>
>Why is it that I can sit in the blazing sun with my car a/c on and have
>it pump out 25deg. air, yet my window a/c that's in the shade dispenses air
>that's nearly 3x as hot?
>
>What do BTU's have to do with the price of apples? This new 6100 BTU a/c is
>replacing a smaller 5000 BTU unit. Those 5000 BTU's would freeze people
>out of the room, but now 6100 BTU's can't even keep the room comfortable.
>What gives? Do BTU's refer to temperature, or just some air displacement?
>
>Enough griping... Does anyone have any suggestions on what kind of a/c I
>should buy? Commercial a/c's in stores freeze people out, why can't I get
>the same perfromance from a smaller window unit?
>
>Jim. (about to move to Alaska)
There are two kinds of heat load, called "sensible" heat
(the temperature), and "latent" heat, which is generated by
the removal of humidity. High humidities make people feel
"clammy" even if the temp is ok.. High humidities also reduce
the sensible (real temp) cooling capacities of units.
To make matters worse, newer is not always better..There have been
a steady stream of "efficiency" gov't regulations which are forced
on new A/C mfgrs. They must achieve higher and higher "SEER's"
(measure of energy efficieny) as time goes on...
One common way to comply with these regs is to raise the
evaporator temp (the inside cooling coils) to be 55F or higher.
This results in moving the SAME BTUs of heat with less electricity
or a few more BTUS of heat with the same electricity., So the 6100
BTU unit is probably just the 5000 BTU unit redesigned for higher
inside coil temps.
Here is the rub. By raising the cooling coil temps, good cooling
efficiency is achieved, but humidity removal goes to zip.
To get good humidity removal, one needs a "lower" efficiency
(older unit), which runs the cooling coils near 32F, not 55-60F
to get the humidity out. Usually, an older unit (properly cleaned
and serviced), will cost only a few bucks more per month, but
will do one hell of a job on the humidity as well.
In some cases a new "high efficiency" unit may actually cost more
to operate than an older unit under humid conditions, since
humidity removal is poor, and thermostat has to be set lower to
achieve comfort..
Good humidity removal also depends on sizing the unit correctly,
so it cools enough and still runs most of the time. A too large
unit will only run 1/2 time or less and not do a good job on
the humidity.
If I were you (and assuming you live in a humid area), I would get
rid of your 6100 BTU unit
Get a used 12,000 BTU (cleaned and in good shape) unit and an
older 5000 BTU unit. When you come home to a hot room, turn 'em
both on (17,000 BTUs), and then shut one of them off, so that
the one which is on runs most of the time to keep the humidity
down.
Car A/C's are rated 3 or 4 "Tons" in capacity, 1 ton = 12000 BTU/hr.
So you have roughly 50,000 BTUs/hr in a car..
Window units use R-22 refrigerant, which does only 1/20 of the
ozone damage as R-12 (in cars), and R-12 is on it's way out.
Using refrigerant "blends" it is possible to increase cooling
capacity and efficiency, and greatly reduce the "pull down"
time (time to do initial cool down when hot).
I invented two such blends (replacements for R-12).
One is R-406A and it will be legal for cars starting Sept 18,1995.
It is EPA SNAP approved for stationary uses now.
A 2nd (no R-number assigned) blend has also been tested for a
time "called GHG HP" for now.
My car, a 1990 Pontiac transport, at 100F outside, R-12 puts
out 56F air. R-406A does 42F air, and "GHG HP" does 28F air
(on the highway), and 35-38F air in the city. But the latter
blend pushes the system harder, higher pressures, etc.
90F outside, raining (100% humidity), GHG-HP achieved 30%
cabin humidity in 4 mins during a 1991 test. Some cars
require a "defrost" timer (under design now) to off the
compressor for 10 sec every 4-5 mins to keep it from
freezing up. Like you, I hate hot humid air and am trying
to do something about it.
--ghg (Inventor R-406A and GHG-HP refrigerants)
http://ghg.ecn.purdue.edu
http://worldserver.com/R-406A
C. Wayne Parker
[stuff deleted]
>Why is it that I can sit in the blazing sun with my car a/c on and have
>it pump out 25deg. air, yet my window a/c that's in the shade dispenses air
>that's nearly 3x as hot?
Believe it or not, your car air conditioner has about 4 to 6 times the
air conditioning capacity of your new home window unit! This is because
when people get in their car they want to be instantly cooled.
--
_______,--------------------------,
/ C. Wayne Parker c...@ornl.gov _/
| Lockheed Martin Energy Systems_/
/_Oak Ridge, Tennessee___USA____/
John Cain
You say;
> I'm a person who likes COLD things-- cold weather, cold beer, and COLD
> air-conditioning.
Well here follows some cold facts about air-conditioning design:
> I'm curious to know why my 12x12 room "isn't air-conditionable" (told to
> me by customer service "professional"), at least not to my standards.
All rooms are 'air-conditionable' as long as you are prepared to put
your money where your mouth is!
> My idea of AC isn't something that reduces outside temperature by 20
> degrees(F)-- coming into an 85deg. room after a day in 105+deg. sun isn't
> exactly my idea of comfort. My idea of AC isn't something that works
> worse as the temperature goes up-- it should be most effective on very
> hot days, when I want the cold air most. My idea of a "temperature" dial
> is not a thermostat(shuts the unit off at a certain temp)-- when I turn
> the dial down, that means I want COLDER air coming out. My idea of AC
> isn't something that blows out 65deg. air for hours and hours trying
> unsuccesfully to cool a 120+deg. room.
It is a professional engineers job to provide a system that works to
the satisfaction of his client (in this instance you), at the most
economical cost in terms of first initial and reduced recurrent energy
costs. You should not have to turn-down your dial! Once set to the
temperature YOU desire, the A/C plant should maintain this temperature at
the design maximum, which you can specify, but beware the higher external
and lower internal design temperatures set by you, could double even tripple
the size of plant required not to mention the need for more complex control
systems that incorporate partial load and dehumidification.
> Imagine if freezers worked the same way as window air-conditioners?
> "Sorry, Mrs Jones... you can't expect your ice cream to be kept solid
> when it's so hot outside. Buy a bigger freezer, maybe that will work."
Do you also reset on a regular basis your freezer dial? Are not the occupants
of your freezer less likely to complain? Set the dial and leave it alone!
If it doesn't do what you want and your engineers say the unit is working
to its maximum capacity, you need a larger unit!
> That's essentially the line I'm getting from the service people. They
> just don't seem to understand that I want my room kept coldest on these
> hot days. They say that's not how a/c's work-- they don't necessarily
> make a room cool, they only make it coolER than it is outside. Blah!
Your engineers are being kind to you. What I perceive they are really
saying is that it is not economicaly viable to achieve what you want.
> So, anyway... I have this new Carrier 6100 BTU window unit. I'd like it to
> cool a 12x12 room TO MY LIKING. They say this unit will never do the job,
> and no "fix" can be made to make it do so. Is this right? Can't they pump
> it up with a different (colder) freon? And do something to the fan so it
> shoots out more air?
The modifications you suggest would have little affect. Dig deep into your
pocket my friend or move to a property with correctly sized A/C.
> Why is it that I can sit in the blazing sun with my car a/c on and have
> it pump out 25deg. air, yet my window a/c that's in the shade dispenses air
> that's nearly 3x as hot?
Correct, good design! Wait a minute, why not sleep in the car? Problem solved!
> What do BTU's have to do with the price of apples? This new 6100 BTU a/c is
> replacing a smaller 5000 BTU unit. Those 5000 BTU's would freeze people
> out of the room, but now 6100 BTU's can't even keep the room comfortable.
> What gives? Do BTU's refer to temperature, or just some air displacement?
The amount of BTU's generaly refers to the cooling load capacity of the unit.
simply put, the more BTU's of heat gain to the room via fabric, solar,
lighting, other casual gains (like you) together with your ventilation load
determines, broadly speaking, the size of plant you require. But be cautious
the size of a unit is affected by a factor known as the sensible to latent heat
ratio which again, simply put, is a ratio of sensible heat, what you would
probably refer to as hot air, to latent heat say humidity. Check the SHR and
sensible cooling capacity of the units referred to above.
> Enough griping... Does anyone have any suggestions on what kind of a/c I
> should buy? Commercial a/c's in stores freeze people out, why can't I get
> the same perfromance from a smaller window unit?
I hope I have not insulted your intelligence with my remarks. I simply want
to raise your awareness that any room can be air-conditioned to the clients
specification at a cost..... what you really must establish is the maximum
internal temperature you are happy with and at what maximum external ambient
condition you will tollerate this temperature, then leave the rest to your
design engineers.
My very best wishes to you Jim.
John Cain
--
.--------------------------------------------------------------------.
| John Cain I.Eng ACIBSE MASHRAE EMail: jo...@bscltd.demon.co.uk |
| BSC Building Services Ltd Tel: 01908 231128 Fax: 231129 |
'--------------------------------------------------------------------'
Allenbau
milligan) writes:
>
>~~>So, anyway... I have this new Carrier 6100 BTU window unit. I'd like
it to
>
>~~>cool a 12x12 room TO MY LIKING. They say this unit will never do the
job,
>~~>and no "fix" can be made to make it do so. Is this right?
>
> Yup.
>
>
Reality just is, pal - Your ideas don't count much - physics do
paul milligan
reyn...@vu-vlsi.ee.vill.edu wrote:
~~>I'm curious to know why my 12x12 room "isn't air-conditionable" (told to
~~>me by customer service "professional"), at least not to my standards.
I doubt that they said anything like that. I bet they said
'not with that little thing in your window'.
~~>My idea of AC isn't something that reduces outside temperature by 20
~~>degrees(F)-- coming into an 85deg. room after a day in 105+deg. sun isn't
~~>exactly my idea of comfort.
Quite true. It doesn't bring outside air in ( assuming the
vent is closed ). It tries to cool the air going into it ( known as
'return air') by 15 to 20 degrees. The outside temp effects how hard it
has to try to work ( within it's limits ),and how much heat is coming into
your room.
My idea of AC isn't something that works
~~>worse as the temperature goes up-- it should be most effective on very
~~>hot days, when I want the cold air most. My idea of a "temperature" dial
~~>is not a thermostat(shuts the unit off at a certain temp)
That's the way it works. The industry's ideas differ from yours.
-- when I turn
~~>the dial down, that means I want COLDER air coming out.
Nope. Never happen. Common myth.
~~>My idea of AC
~~>isn't something that blows out 65deg. air for hours and hours trying
~~>unsuccesfully to cool a 120+deg. room.
It doesn't 'blow out' air of a certain temp. It tries to lower the
temp of the air it cirvulates by a certain amount ( 15 - 20 ). Different
concept.
~~>Imagine if freezers worked the same way as window air-conditioners?
~~>"Sorry, Mrs Jones... you can't expect your ice cream to be kept solid
~~>when it's so hot outside. Buy a bigger freezer, maybe that will work."
Put that freezer outside in 105 and see what happens. :~)
~~>That's essentially the line I'm getting from the service people.
They are telling you the truth. Believe them or not as you see fit.
~~>They
~~>just don't seem to understand that I want my room kept coldest on these
~~>hot days.
They understand that well, I promise you. You don't understand
how AC works, nor that service techs are mechanics, not magicians.
~~>They say that's not how a/c's work-- they don't necessarily
~~>make a room cool, they only make it coolER than it is outside. Blah!
See above. Blah.
~~>So, anyway... I have this new Carrier 6100 BTU window unit. I'd like it to
~~>cool a 12x12 room TO MY LIKING. They say this unit will never do the job,
~~>and no "fix" can be made to make it do so. Is this right?
Yup.
~~>Can't they pump
~~>it up with a different (colder) freon? And do something to the fan so it
~~>shoots out more air?
Nope and Nope, respectively.
~~>What do BTU's have to do with the price of apples?
Very little. A great deal, however, to do with the capacity of your
AC. And the temperature of the apples in your room <G>.
~~>This new 6100 BTU a/c is
~~>replacing a smaller 5000 BTU unit. Those 5000 BTU's would freeze people
~~>out of the room,
In 105 ambient ?
~~>Enough griping... Does anyone have any suggestions on what kind of a/c I
~~>should buy?
Sure do. A bigger one.
~~>Commercial a/c's in stores freeze people out, why can't I get
~~>the same perfromance from a smaller window unit?
Because you didn't pay the money they paid for a bigger unit.
You want $10 worth out of a $5 unit. Ain't gonna get it.
Paul
Dave Munro
[snip]
>John Cain
Jim talked to a customer service 'professional'. I presume that means he talked to a
salesman at an appliance store. The salesman was put in a corner to defend a sale
and product.
I seriously doubt he discussed this with a professional engineer. Not many people go
to professional engineers for selecting window mounted air conditioning units. If
they did, professional engineers may be hard pressed in making a recommendation, in
that the engineer is obligated to make recommendations that are legal (and comply
with local energy codes). The energy code prescribes an indoor design temperature of
78 degrees, and outdoor temperatures that are 15 to 20 degrees less than the extreme
outdoor temperatures found at a given locale. The energy codes (aka government
intervention) and standards passed down to manufacturers (additional government
intervention) have changed the conventions.
I would characterize Jim as a consumer that isn't having his expectations met. Why
not?
reyn...@vu-vlsi.ee.vill.edu
>~~>I'm curious to know why my 12x12 room "isn't air-conditionable" (told to
>~~>me by customer service "professional"), at least not to my standards.
> I doubt that they said anything like that. I bet they said
>'not with that little thing in your window'.
Umm, no, sorry... they said that my room will not be cold (like I
described) with _any_ air-conditioner.
Something to the effect of-- BTUs are BTUs and one 6000 BTU model won't be
any colder than another. I asked about the possibility of using a larger
unit, and I was told that I shouldn't. They said 10,000 BTU was greatly
oversized for a room of this size, and it wouldn't de-humidify properly.
>~~> My idea of AC isn't something that works
>~~>worse as the temperature goes up-- it should be most effective on very
>~~>hot days, when I want the cold air most. My idea of a "temperature" dial
>~~>is not a thermostat(shuts the unit off at a certain temp)
> That's the way it works. The industry's ideas differ from yours.
Well, the industry's idea sucks! :-) I'll do my job and shut the a/c
off when I get cold, but in the mean time it should be making me cold!
When it's 105 degrees outside, I want it to cool much more quickly with
much cooler air than when it's 75 out. Doesn't that make sense? So why
don't they work that way?!
> It doesn't 'blow out' air of a certain temp. It tries to lower the
>temp of the air it cirvulates by a certain amount ( 15 - 20 ). Different
>concept.
Then why doesn't the air coming out ever get lower than 60 degrees?
> They understand that well, I promise you. You don't understand
>how AC works, nor that service techs are mechanics, not magicians.
Magicians. Heh. They sure as hell made my money disappear, and they left
me with a hot room!
>~~>Can't they pump
>~~>it up with a different (colder) freon? And do something to the fan so it
>~~>shoots out more air?
> Nope and Nope, respectively.
If the fan speed is increased, would that increase the BTUs? If more heat
was removed from the air, would that increase the BTUs? If the unit was
charged with a colder freon (car freon?), would the air be any colder?
>~~>This new 6100 BTU a/c is
>~~>replacing a smaller 5000 BTU unit. Those 5000 BTU's would freeze people
>~~>out of the room,
> In 105 ambient ?
Maybe not at 105 degrees. But comparing the 5000BTU performance with that
of the new 6100BTU unit. If I left that 5000BTU unit on high-cool all
night long, it'd be VERY COLD in the morning(like several thick blankets
cold). But with the 6100 unit, it runs for days and days and sometimes
can't even keep the room comfortable.
>~~>Enough griping... Does anyone have any suggestions on what kind of a/c I
>~~>should buy?
>
> Sure do. A bigger one.
Every know-be I've ever talked to about air-conditioning has warned
against using a bigger unit than what's recommended. Something about it
not removing moisture, and the compressor may shut off prematurely.
>~~>Commercial a/c's in stores freeze people out, why can't I get
>~~>the same perfromance from a smaller window unit?
> Because you didn't pay the money they paid for a bigger unit.
>You want $10 worth out of a $5 unit. Ain't gonna get it.
I just want my room cool! All the comsumer guide sheets say that a 6100BTU
unit is more than enough for a 12x12 room, but this one has to run for
hours and hours before you even notice temperature change.
John Cain
>
> John Cain <jo...@bscltd.demon.co.uk> wrote:
> >In article: <3ue0d8$7...@vu-vlsi.ee.vill.edu> reyn...@vu-vlsi.ee.vill.edu writes:
> >Poor Jim,
> >John Cain
> Jim talked to a customer service 'professional'. I presume that means he talked to a
> salesman at an appliance store. The salesman was put in a corner to defend a sale
> and product.
> I seriously doubt he discussed this with a professional engineer. Not many people go
> to professional engineers for selecting window mounted air conditioning units. If
> they did, professional engineers may be hard pressed in making a recommendation, in
> that the engineer is obligated to make recommendations that are legal (and comply
> with local energy codes). The energy code prescribes an indoor design temperature of
> 78 degrees, and outdoor temperatures that are 15 to 20 degrees less than the extreme
> outdoor temperatures found at a given locale. The energy codes (aka government
> intervention) and standards passed down to manufacturers (additional government
> intervention) have changed the conventions.
> I would characterize Jim as a consumer that isn't having his expectations met. Why
> not?
Please excuse my ignorance of you energy codes in the US and accept my appologies for
presuming to understand the problem. I quite understand now why 'poor Jim' could not
consult a PE and why he, and no doubt numerous others, suffer when summertime temps
exceed design parameters. I am puzzled though, how on earth did the government derive
such restrictive parameters?
In the UK we would welcome a spell of 95-100, perhaps with more conservative vapour
pressures though! ;-)>
John Mills
it to
> >cool a 12x12 room TO MY LIKING. They say this unit will never do the
job,
> >and no "fix" can be made to make it do so. Is this right? Can't they
pump
> >it up with a different (colder) freon? And do something to the fan so
it
> >shoots out more air?
I have a Carrier 6100 BTU unit, model 51BTY706161. It is really noisy but
have no complaints about cooling. It is in a SW window, 15x15 room. Last
week we had overnight lows in the upper 70s. My bedroom stayed 66 degrees,
right where I wanted it. The house has central air but in mild weather,
the window unit can do the whole house (1000 sq ft) so the central stays
off. The other day at 90 out, the central was off and the window unit
held the house to 75. I was impressed. More airflow? That means warmer
discharge and high humidity. A/Cs run approximately 400 CFM per ton so
that 1/2 ton unit should move about 200 CFM of air. Air conditioners are
on & off. That's why the thermostat cannot vary the temperature of the
discharge air, but only cycle the compressor on & off.
Rick Nyman
>any colder than another. I asked about the possibility of using a larger
>unit, and I was told that I shouldn't. They said 10,000 BTU was greatly
>oversized for a room of this size, and it wouldn't de-humidify properly.
If the system is running constantly, shouldn't it dehumidify? (Of
course, this is assuming a reasonable evaporator temp) Unless the
unit was oversized to the point that it started cycling, I don't think
this would happen.
>When it's 105 degrees outside, I want it to cool much more quickly with
>much cooler air than when it's 75 out. Doesn't that make sense? So why
>don't they work that way?!
Ok, here comes some thermodynamics (duck). For the perfect heat pump
(Carnot cycle):
Ql=(Tl/Th)*W where Ql is the heat transfer at the evaporator, Th is
the absolute temperature at the condenser, and Tl is the temperature
at the evaporator. W is the compressor work.
So, assuming that W stays constant, your air conditioner has 96% of
the power at 100F outdoors as it does at 80F outdoors. That's
thermodynamics for a perfect system. So you're not going to do that
well. In the real world, the second law efficiency (efficiency over
Carnot efficiency) will decrease as you move away from the design
points. The unit is most certainly NOT designed for 100+F outdoor
temperatures and the compressor loses efficiency as it attempts to
raise the condenser temperature to increase temperature.
>Then why doesn't the air coming out ever get lower than 60 degrees?
The temperature of the evaporator (cold) and condenser (hot) are
determined by the pressure of the evaporating/condensing refrigerant
(aka Freon). The system is designed to work best with certain
pressures. In hot weather, it has to raise the pressure of the
condenser to raise its temperature (so it gives off heat).
Conversely, the system needs to lower evaporator pressure to lower
temperature. It's got design points and may not be capable of
lowering the pressure enough to get the temperature you're looking
for.
>> They understand that well, I promise you. You don't understand
>>how AC works, nor that service techs are mechanics, not magicians.
>If the fan speed is increased, would that increase the BTUs? If more heat
>was removed from the air, would that increase the BTUs? If the unit was
>charged with a colder freon (car freon?), would the air be any colder?
If the air remained the same temperature, then increasing the fan
speed would increase the number of BTUs of heat removed from the room.
However, if you increase the fan speed on a unit, you'll find that the
temperature rises (because the amount of cooling is determined, at
least partially, by the mass flow of refrigerant
evaporating/condensing and the heat of vaporization of the same (you
can't control the latter - it's a property of the refrigerant and the
former is designed in)
>Every know-be I've ever talked to about air-conditioning has warned
>against using a bigger unit than what's recommended. Something about it
>not removing moisture, and the compressor may shut off prematurely.
If the unit is small enough to run constantly, then it should remove
plenty of humidity. Anyone?
>I just want my room cool! All the comsumer guide sheets say that a 6100BTU
>unit is more than enough for a 12x12 room, but this one has to run for
>hours and hours before you even notice temperature change.
There is more to a room than its size. Is there something about your
room that might make it need more cooling? (Sunny side of house, poor
insulation, door standing open, hole in ceiling, fireplace with fire
burning, etc)
Just for kicks, what's the temperature of the air in the room and
what's the vent temperature (hard to guess - easy to measure)?
--
Rick Nyman <eny...@vt.edu>
A recent graduate of Virginia Tech's Mechanical Engineering department.
(Still looking for a job)
Home Page: http://sfbox.vt.edu:10021/E/enyman/index.html
My ASMEnet account: nyman...@asme.org
leftyj
>When it's 105 degrees outside, I want it to cool much more quickly with
>much cooler air than when it's 75 out. Doesn't that make sense? So why
>don't they work that way?!
fine- turn the heat on also when it gets cool in the room. you will
warm the air coming out of the machine- hence, less cooling when the
room is comfortable. (I'm joking- your electric bill would be awful!)
How much can you expect from a tiny $300 WINDOW air-conditioner?
>If the fan speed is increased, would that increase the BTUs? If more heat
>was removed from the air, would that increase the BTUs? If the unit was
>charged with a colder freon (car freon?), would the air be any colder?
Increasing the fan speed would warm the air coming out- generally
the faster the fan the higher the temp and the higher the humidity.
car freon (r-12) might already be in your unit. it would not work well
with r-12.
>Every know-be I've ever talked to about air-conditioning has warned
>against using a bigger unit than what's recommended. Something about it
>not removing moisture, and the compressor may shut off prematurely.
they're not living in your house. they might not know all the facts-
like if you leave the door open alot, for example.
>I just want my room cool! All the comsumer guide sheets say that a 6100BTU
>unit is more than enough for a 12x12 room, but this one has to run for
>hours and hours before you even notice temperature change.
how new is the unit? could you return it to the store? could you return
it to the manufacturer? buy another and see if it works better. then
demand satisfaction.
John
Steve Lewellen
>From: John Cain <jo...@bscltd.demon.co.uk>
>Subject: Re: AC doesn't work when it's _HOT_ outside!
>Date: Mon, 17 Jul 1995 20:20:34 GMT
>It is a professional engineers job to provide a system that works to
>the satisfaction of his client (in this instance you), at the most
>economical cost in terms of first initial and reduced recurrent energy
>costs.
A very important point missed here, is that in the U.S. most states have
strict energy code compliances, such as design parameters. Therefore
depending on the application there may not be 100% satisfaction from the
client if they are looking for an un-realistic 25F delta.