The impression I got here is that if your AC is too big, it will cool
the house before it can get rid of the humidity.
(This surprises me -- I would have thought it would be the same no
matter the size of the AC -- but no one who knows anything has
contradicted anyone who said this. I certainly don't know enough to
And then you will be left with a cool but still damp house. Now I
would think if you already have an AC that is too big for your house,
there would be a way to solve this problem,, but I don't remember that
So I am going to give my usual type of suggestion. Get a decent**
hygrometer and take it with you when you go to friends' homes, or even
to work and shopping maybe (unless there is some reason why such
places are different) and the homes are comfortable, see what their
humidity is, and then measure yours. There must be a pretty broad
range of what is comfortable, and if you go to enough friends, you'll
learn what is comfortable for you.
**It might not even have to be accurate, since the goal is not to
measure things and keep records, but to compare the readings at your
friends with your own house. To do that it only has to repsond to
humidity and go up when it's higher and down when it's less.
I suspect there is a little more to the story than this.
Is there an existing problem? If so what is the problem?
In general, the proper sizing and installation of an A/C unit is
critical for comfort and the prevention of mold etc. Having a good
tech who is familiar with the local conditions and construction is
What is the story? Why do you have a question? What is the real
On Sun, 10 Aug 2008 03:32:37 -0700 (PDT), firstname.lastname@example.org
There is no more to the story. I am just a careful home owner who is
new to the South, and it's climate. I want to be sure the humidity
level in my villa is not too high. There is no problem as I can see.
The HVAC unit is 8 yrs old and serviced regularly. I am getting a
consistent reading of 60%, and want to know if this is appropriate.
Does sound a bit high. Here in the
Chicago area, when my AC unit was
way too small (it would run for 10 or 12
hours on a 92 degree day) the
humidity was very well controlled at
about 30 or 35%. After putting in
the next size unit (36K --> 42K BTU), it
went up a little, but, of course,
ran much less. After adding much
insulation and new windows, it went
up even more, maybe around 40 - 45%. It
still feels ok. I'm especially
interested in this thread because, after
living in this area all my 60 years,
I am building in the western mountains
of NC and I am curious what to
expect in the south.
The answer is your personal comfort.
I find if I cool the house to 80* and have the humidity down to 40%,
If the humidity is 60% I need to have it 74* or 75* to be comfortable.
I'm not happy with my air conditioner and it's humidity control. I bought
a dehumidifier and run it to bring the humidity down to the 40%. This is not
a happy solution because the dehumidifer produces a lot of heat and the room
it is in gets
The next post will probably say, "your air conditioner's too big, get a
Well it might be or maybe not. I don't think it short cycles, but that is on
my list to monitor.
The air conditioner is old (between 17 and 35 years). If I buy a new more
efficient one it will take many, many years to break, considering the $4,000
to $5000 that it would cost to install. I'll get a new one when I'm forced
As you don't want to replace now, you
might try to lower your blower speed.
Of course, you have to make sure it
doesn't ice up. I have an older AC unit
is too large, due to better windows and
insulation. I have lowered the blower
speed which takes our more moisture and
also makes less noise.
Generally 40 - 60% humidity is considered good. Too dry and you
can experience problems and mold start just above 60%
Note: tools to measure humidity vary greatly. Some are not very
accurate and others are poorly calibrated. Since you are close to
that 60% area, I think I would want a second opinion (different kind
of meter) check. Remember that as you get close to the design limit
of the A/C unit, you will be getting lower humidity and you will get
less reduction of humidity when you move either direction.
I don't know the answer, but FWIW I'm in Austin, Texas, and our
indoor humidity tends to fluctuate around 45% in the summer, as
measured by one of those little Radio Shack meters. I suspect as
you move towards the coast (e.g. Houston) that value would rise a
bit, and further inland (e.g. Amarillo) it would be lower.
And different houses, local weather and thermostat settings surely
will result in some differences, as well.
The e-mail address in our reply-to line is reversed in an attempt to
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Humidistats of the analog type are rarely accurate new, they have to
be calibrated, if they can, many cant. Digital are usualy better. To
calibrate a analog-dial type wrap it in a moist rag for 30 minutes and
set to 95%. Go to a store that has a big display of dial units and you
will see them all at different settings, maybe 15% off, each other for
name brand Taylors. If you are to humid feeling maybe get a
dehumidifier as your AC is likely to large. I tried a lower blower
speed but I just use a dehumidifier now. A lower blower speed can
freeze your coil.
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