We have moved into a house that has central AC. We've never had or used
central AC before but it's very humid here in the South so we've set the
thermostat at 78 degrees to dehumidify the house.

I'm baffled as to why the AC is running in the morning even when the outdoor
temperature is significantly cooler. This morning, for example, it was 58
degrees outdoors and the indoor temperature was 78 degrees with the AC
running. The only source of heat that I can think of is from the
refrigerator. The hot water heater is in the basement.

I understand why a house requires cooling during the day even when it cooler
outdoors but I'm totally clueless as to why the house would need AC in the
early morning after the house has been cooling down for over 10 hours. I'm
especially baffled because yesterday it was mostly cloudy and cool.

"LuckyDucky" wrote in message

I'm baffled as to why the AC is running in the morning even when the
outdoor
temperature is significantly cooler. This morning, for example, it was 58
degrees outdoors and the indoor temperature was 78 degrees with the AC
running.

I understand why a house requires cooling during the day even when it
cooler
outdoors but I'm totally clueless as to why the house would need AC in the
early morning after the house has been cooling down for over 10 hours.

Every running appliance gives off heat. Your body gives off heat (800
btu/hr IIRC), light bulbs, the toaster, etc.

If your house is well insulated, it is not giving off the heat to the
outdoors rapidly. The unit is controlled by the thermostat indoors. Open
the windows and let in that beautiful cool air.

If the air is dry, open the windows at night and turn on a window fan to
draw the air through.
Ed

"jim" wrote in message ...
LuckyDucky wrote:

snip

the next morning when the a/c kicks in go into your attic and see how
hot it is up there( i live in South Louisiana) and you cant stay in an
attic in this area for very long...its real hot....
or step up on a step stool to change some light bulbs and see how much
hotter it is in the upper top of your rooms... heat coming in through
the sheetrock on the ceiling........ you live in the south and its
58 deg???? is this an old message??? its marked july 12... i cannot
remember any july where the temp was 58 deg......

Yes, this is a fresh message (July 12, 2003). It was 58 degrees (what a
relief!) right before the sun rose. The ground was covered in condensation
as if there was a rainstorm. By noon, it was in the mid-80's.

"Joseph Meehan" wrote in message
...
Because it is more than 78º in side and to keep it there it needs to
run. You could open up windows and run a fan to get it below 78º but that
would let in so much moisture, the A/C would run longer to get rid of that
extra moisture than it now runs to keep it down to 78º.

Actually, that's not completely correct.

If the homeowner has a combination thermostat/humidistat that will turn on
the A/C to lower humidity, you make an excellent point. In other words,
most current Tstats have no way to measure the %RH in the house.

Otherwise, the Tstat is just reading the heat level in the house.

LuckyDucky spaketh...

...we've set the thermostat at 78 degrees

I'm baffled as to why the AC is running...
...and the indoor temperature was 78

....and the indoor temperature was 78
....we've set the thermostat at 78 degrees

....and the indoor temperature was 78
....we've set the thermostat at 78 degrees

....and the indoor temperature was 78
....we've set the thermostat at 78 degrees

....and the indoor temperature was 78
....we've set the thermostat at 78 degrees

....and the indoor temperature was 78
....we've set the thermostat at 78 degrees


get it
--
McQualude

In alt.home.repair on Sat, 12 Jul 2003 18:47:57 -0400 "HeatMan"
posted:


"Joseph Meehan" wrote in message
.. .
Because it is more than 78º in side and to keep it there it needs to
run. You could open up windows and run a fan to get it below 78º but that
would let in so much moisture, the A/C would run longer to get rid of that
extra moisture than it now runs to keep it down to 78º.

Actually, that's not completely correct.

If the homeowner has a combination thermostat/humidistat that will turn on
the A/C to lower humidity, you make an excellent point. In other words,
most current Tstats have no way to measure the %RH in the house.

Otherwise, the Tstat is just reading the heat level in the house.

Yes, but I think it is harder, that is, takes longer, takes the
removal of more heat, to cool humid air than to cool dry air. I can't
explain this well -- the boundary between water and ice might be more
explainable -- but somewhere in the cooling process one has to cool
the water vapor until it condenses into water itself again. Obviously
it's not 212 degrees farhrenheit in the house, but there is still some
temperature where the humidity condenses into water, and it takes a
lot of cooling to do that.

One would think one could just cool the air and leave the humidity
high, but the laws of physics and the AC won't let that happen. The
maximum amount of water in the air is lower when the air is cooler.
So when the air gets cooler, some water has to condense out. But in
the process of cooling that water vapor from X degrees as a gas to the
same temperature, X degrees as a liquid, the gas gives up a lot of
heat, heat that has to be removed by the AC.


The one big question this leaves is: Is the relative humidity inside a
a room with AC always 100% (or near there). I don't understand why it
wouldn't be, but by personal experience I don't think it is that high.
It doesn't seem humid but maybe that is just because it is cool.

Does anyone know?



I think the humidistat means that the AC will run even when it is
below the set temperature, until the humidity is at the desired level.
But iiuc, it does this by cooling the air some more and driving out
the water. Maybe there is some arrangement of the cooling coils that
reduces humidity more efficiently than it lowers temp. Does anyone
know?

Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.

On Sat, 12 Jul 2003 12:16:40 -0400, "LuckyDucky"
wrote:
[snip...snip...]
I understand why a house requires cooling during the day even when it cooler
outdoors but I'm totally clueless as to why the house would need AC in the
early morning after the house has been cooling down for over 10 hours. I'm
especially baffled because yesterday it was mostly cloudy and cool.

Insulation works both ways. Or, rather, a 20 degree delta T is the same
when it's 58 outside, 78 inside as when it's 48/68 or 38/58 (to a first
approximation). In addition to appliances, *you* give off heat as well
(cf: The Matrix) so there's still heat energy that needs to be removed.

Another effect is stratification. At night, with the occupants quiet and
minimal differential heating, the air will tend to settle into layers.
As people move about, or as the sun hits one side of the house, you'll
see mixing of the layers and at some point the thermostat kicks on.

--
Rich Webb Norfolk, VA

HvacTech2 wrote:

Hi meirman, hope you are having a nice day

On 12-Jul-03 At About 16:06:07, meirman wrote to All
Subject: Why is AC running in the morning when it's cooler outdoors?

m From: meirman

m In alt.home.repair on Sat, 12 Jul 2003 18:47:57 -0400 "HeatMan"
m posted:

m Yes, but I think it is harder, that is, takes longer, takes the
m removal of more heat, to cool humid air than to cool dry air.

This is true

m The maximum amount of water in the air is lower when the air is cooler.

This is where your theory goes wrong. To a certain extent cooling with A/C
does dehumidify. but as the air gets colder it can hold more humidity. Think
of it as condensing the air smaller. when you get too cold the air can hold
more "relative" humidity. the only way to reduce it at this point is to
reheat it and expand the air so the relative humidity decreases.

m So when the air gets cooler, some water has to condense out. But in
m the process of cooling that water vapor from X degrees as a gas to
m the same temperature, X degrees as a liquid, the gas gives up a lot
m of heat, heat that has to be removed by the AC.

m The one big question this leaves is: Is the relative humidity inside
m a a room with AC always 100% (or near there). I don't understand
m why it wouldn't be, but by personal experience I don't think it is
m that high. It doesn't seem humid but maybe that is just because
m it is cool.

m Does anyone know?

m I think the humidistat means that the AC will run even when it is
m below the set temperature, until the humidity is at the desired
m level. But iiuc, it does this by cooling the air some more and
m driving out the water. Maybe there is some arrangement of the cooling
m coils that reduces humidity more efficiently than it lowers temp.
m Does anyone know?

as explained above you need to reheat that air to dehumidify it.

-= HvacTech2 =-

.. "Why is the alphabet in that order? Is it because of that song?"- s.w.

___ TagDude 0.92á+[DM]
++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++
spam protection measure, Please remove the 33 to send e-mail

That's about as twisted an explanation as you can get. It's
much simpler to forget humidity and relative humidity and to
focus on the actual amount of water in air. The key is how
much water the air will hold, and hot air will hold a lot
more water than cold air. So as air is cooled, water
condenses out at some temperature. Relative humidity only
means how much water the air actually holds compared to how
much it is capable of holding at a specific temperature. As
air is cooled the relative humidity increases although the
actual water content remains unchanged until the temperature
is reached where the humidity is 100 percent and then the
actual water content of the air decreases as the excess
water condenses into a liquid.

The answer to meirman's question is that no, the relative
humidity in an air conditioned room is not always 100
percent. If you live in a arid climate the humidity in an
air conditioned room is seldom, if ever, 100 percent. In
our house, the relative humidity is usually about 60
percent. The relative humidity of the air outside is often
close to 30 percent. The reason we don't have 100 percent
humidity is simple, we aren't taking hot air with lot of
water content and cooling it. When we close our house and
start the air conditioning, the temperature is usually 72-76
degrees and we set the temp for 74-75 degrees, therefore the
great mass of air in the house doesn't really change in
temperature or water content, the AC just maintains the
temperature. Only the replacement air throughout the day
starts out hot and ends up cool and that hot air often has a
low humidity so very little water is condensed out of the
air as it is cooled. In contrast, in the east the outside
hot air may have lots of water and cooling the replacement
air from 90 degrees to 72 degrees may result in lot of water
condensing out of the air.

"jagerEd" wrote

Do you have any unshaded east facing windows?

Ed


Yes, we have unshaded windows on all sides of the house.

I'm aware of the greenhouse effect -- ultraviolet light converted to
infrared light (heat) as the light passes through glass.

However, late yesterday afternoon was wet and cool. At 12am, the outdoor
temperature was 60 degrees. This morning, the indoor temperature was 78
degrees. The thermostat was set at 80 so the AC didn't kick in. Last night,
we slept with the bedroom windows open with the door closed. That would
exclude us as being the cause of generating enough BTU's to heat the house
by 20 degrees.

Responding to an earlier post; we don't have an attic; we have rooms
upstairs that are also air-conditioned. We do have a finished basement
which is cooler than the rest of the house.

I hope that this situation continues into winter -- we won't have to use the
furnace.

So far, I see lots of ideas being tossed, but NO ONE has stated the simple
facts..

Your home..its a heat bank...its being heated all day long, and that heat is
making its way to the inside. When you wake up in the morning, the heat that
is indoors, other than the heat created by your electrical that might be on
all night, such as lights, power supplys, etc, and the heat given off by you
, and all living things in the home that is added to the load.
The home was heated all day, and that heat is finding its way into the home
at night..its been stored in every inch of the home...come morning, its
still radiating into the home..
Not a big deal.

"LuckyDucky" wrote in message
...

"jagerEd" wrote

Do you have any unshaded east facing windows?

Ed


Yes, we have unshaded windows on all sides of the house.

I'm aware of the greenhouse effect -- ultraviolet light converted to
infrared light (heat) as the light passes through glass.

However, late yesterday afternoon was wet and cool. At 12am, the outdoor
temperature was 60 degrees. This morning, the indoor temperature was 78
degrees. The thermostat was set at 80 so the AC didn't kick in. Last
night,
we slept with the bedroom windows open with the door closed. That would
exclude us as being the cause of generating enough BTU's to heat the house
by 20 degrees.

Responding to an earlier post; we don't have an attic; we have rooms
upstairs that are also air-conditioned. We do have a finished basement
which is cooler than the rest of the house.

I hope that this situation continues into winter -- we won't have to use
the
furnace.

Am I the only one who thinks this is not normal, other than
LickyDucky? His house has no attic - just A/C rooms. The entire
house is cooled to 78 and it is 58 outside? Any heat they can create
should be going to the big heat sink outside. How does the house heat
back up to 79 to make the A/C kick back on? Where is the big heat
source? A fridge and couple of people can't create that much heat. Of
course, eventually those sources and all the other heat sources will
cause the A/C to kick back on sometime depending on insulation. But
it should not be very frequent. Is the A/C running long, or just a
little. Could it be off 90% of the night and is just coincidence it
is running when you wake?

In my experience with A/C in South Louisiana and Florida, all houses
I've lived in, (all with non A/C attics), did not have the air running
when the thermostat was set at 78 and the outside temp was below 65 -
aproximately.

As has been mentioned, check for a humidity control.

If the A/C is coming on and off, then it is probably working. To
check, just take the temp of the air coming out of a register as
another poster suggested. It should be at least 15-20 F cooler than
the return air. Also, see if water is dripping from the coils? It is
usually routed outside or to a drain.

Another problem which is not common is the placement of the
thermostat. It could be near a heat source, or have a vent blowing
right on it, causing the A/C to shut down too early.






"LuckyDucky" wrote in message ...
We have moved into a house that has central AC. We've never had or used
central AC before but it's very humid here in the South so we've set the
thermostat at 78 degrees to dehumidify the house.

I'm baffled as to why the AC is running in the morning even when the outdoor
temperature is significantly cooler. This morning, for example, it was 58
degrees outdoors and the indoor temperature was 78 degrees with the AC
running. The only source of heat that I can think of is from the
refrigerator. The hot water heater is in the basement.

I understand why a house requires cooling during the day even when it cooler
outdoors but I'm totally clueless as to why the house would need AC in the
early morning after the house has been cooling down for over 10 hours. I'm
especially baffled because yesterday it was mostly cloudy and cool.

meirman wrote:

In alt.home.repair on Sat, 12 Jul 2003 18:47:57 -0400 "HeatMan"
posted:


"Joseph Meehan" wrote in message
. ..


Because it is more than 78º in side and to keep it there it needs to
run. You could open up windows and run a fan to get it below 78º but that
would let in so much moisture, the A/C would run longer to get rid of that
extra moisture than it now runs to keep it down to 78º.


Actually, that's not completely correct.

If the homeowner has a combination thermostat/humidistat that will turn on
the A/C to lower humidity, you make an excellent point. In other words,
most current Tstats have no way to measure the %RH in the house.

Otherwise, the Tstat is just reading the heat level in the house.



Yes, but I think it is harder, that is, takes longer, takes the
removal of more heat, to cool humid air than to cool dry air. I can't
explain this well -- the boundary between water and ice might be more
explainable -- but somewhere in the cooling process one has to cool
the water vapor until it condenses into water itself again. Obviously
it's not 212 degrees Fahrenheit in the house, but there is still some
temperature where the humidity condenses into water, and it takes a
lot of cooling to do that.

One would think one could just cool the air and leave the humidity
high, but the laws of physics and the AC won't let that happen. The
maximum amount of water in the air is lower when the air is cooler.
So when the air gets cooler, some water has to condense out. But in
the process of cooling that water vapor from X degrees as a gas to the
same temperature, X degrees as a liquid, the gas gives up a lot of
heat, heat that has to be removed by the AC.

The one big question this leaves is: Is the relative humidity inside a
a room with AC always 100% (or near there). I don't understand why it
wouldn't be, but by personal experience I don't think it is that high.
It doesn't seem humid but maybe that is just because it is cool.
Does anyone know I think the humidistat means that the AC will run even when it is
below the set temperature, until the humidity is at the desired level.
But iiuc, it does this by cooling the air some more and driving out
the water. Maybe there is some arrangement of the cooling coils that
reduces humidity more efficiently than it lowers temp. Does anyone
know? Meirman


It's time to get some straight scoop on latent heat removal. To save NG
space read pages. - Darrell

--
Air Conditioning - Latent Heat Removal -
http://www.udarrell.com/air-conditio...tent-heat.html

"L. Borne" wrote :

Am I the only one who thinks this is not normal, other than
LickyDucky? His house has no attic - just A/C rooms. The entire
house is cooled to 78 and it is 58 outside? Any heat they can create
should be going to the big heat sink outside. How does the house heat
back up to 79 to make the A/C kick back on? Where is the big heat
source? A fridge and couple of people can't create that much heat. Of
course, eventually those sources and all the other heat sources will
cause the A/C to kick back on sometime depending on insulation. But
it should not be very frequent. Is the A/C running long, or just a
little. Could it be off 90% of the night and is just coincidence it
is running when you wake?

The A/C kicks in every now and then. The entire system had its bi-yearly
maintenance done by a HVAC company a few weeks ago.

In my experience with A/C in South Louisiana and Florida, all houses
I've lived in, (all with non A/C attics), did not have the air running
when the thermostat was set at 78 and the outside temp was below 65 -
approximately.

As has been mentioned, check for a humidity control.

According to my meter, the indoor RH is about 33-35%.

If the A/C is coming on and off, then it is probably working.

The A/C is cycling on and off. Seems normal. The cooler it is outdoors,
the less it runs.

To
check, just take the temp of the air coming out of a register as
another poster suggested. It should be at least 15-20 F cooler than
the return air. Also, see if water is dripping from the coils? It is
usually routed outside or to a drain.


I haven't measured the temperature coming out of the register yet, but it
feels mighty cool.
Water is dripping out of the drain. When it's hot out, then there's a
gusher coming out of the drain pipe to the outdoors.

Another problem which is not common is the placement of the
thermostat. It could be near a heat source, or have a vent blowing
right on it, causing the A/C to shut down too early.


The thermostat is not near any heat sources (lights, appliances, fans etc.).
At night, nothing except for the refrigerator (which is about 15 feet away
from the thermostat) is left on that would generate any heat. Heck, we
don't even use the oven very much so that it won't heat up the house. In
addition, the TV and the computer is downstairs. We don't spend much time
upstairs.

I understand why some people believe that the heat could be "leaking" in
through the walls from the daytime heat but there have been those days when
it has been cool and cloudy.

Mind you, I'm not concerned, worried or upset about the A/C coming on from
time to time when it's 20 degrees cooler outdoors. I'm simply curious as to
why/how this is happening when there's no *apparent* heat source.

Mind you, I'm not concerned, worried or upset about the A/C coming on from
time to time when it's 20 degrees cooler outdoors. I'm simply curious as to
why/how this is happening when there's no *apparent* heat source.

Personally, I'd go looking for the heat source... Or just turn the
AC off some day, and see what the temp in the house does.

Learn what a manual J and T are, and latent heat is included...and yes..it
happens...

Hell..it was 65 this morning and my air was on at 75 and the air kicked
on.....it happens...but then, you learn that after years in the biz, and a
few dozen courses in thermal dynamics..storage....and such...

"L. Borne" wrote in message
om...
Am I the only one who thinks this is not normal, other than
LickyDucky? His house has no attic - just A/C rooms. The entire
house is cooled to 78 and it is 58 outside? Any heat they can create
should be going to the big heat sink outside. How does the house heat
back up to 79 to make the A/C kick back on? Where is the big heat
source? A fridge and couple of people can't create that much heat. Of
course, eventually those sources and all the other heat sources will
cause the A/C to kick back on sometime depending on insulation. But
it should not be very frequent. Is the A/C running long, or just a
little. Could it be off 90% of the night and is just coincidence it
is running when you wake?

In my experience with A/C in South Louisiana and Florida, all houses
I've lived in, (all with non A/C attics), did not have the air running
when the thermostat was set at 78 and the outside temp was below 65 -
aproximately.

As has been mentioned, check for a humidity control.

If the A/C is coming on and off, then it is probably working. To
check, just take the temp of the air coming out of a register as
another poster suggested. It should be at least 15-20 F cooler than
the return air. Also, see if water is dripping from the coils? It is
usually routed outside or to a drain.

Another problem which is not common is the placement of the
thermostat. It could be near a heat source, or have a vent blowing
right on it, causing the A/C to shut down too early.






"LuckyDucky" wrote in message
...
We have moved into a house that has central AC. We've never had or used
central AC before but it's very humid here in the South so we've set the
thermostat at 78 degrees to dehumidify the house.

I'm baffled as to why the AC is running in the morning even when the
outdoor
temperature is significantly cooler. This morning, for example, it was
58
degrees outdoors and the indoor temperature was 78 degrees with the AC
running. The only source of heat that I can think of is from the
refrigerator. The hot water heater is in the basement.

I understand why a house requires cooling during the day even when it
cooler
outdoors but I'm totally clueless as to why the house would need AC in
the
early morning after the house has been cooling down for over 10 hours.
I'm
especially baffled because yesterday it was mostly cloudy and cool.

I've had a few courses in Thermodynamics when I got my aerospace
engineering degree, and use thermo often. However, you don't need
more than common sense to know that if the entire volume of the house
is 78 and the outside air temp is 58, then something is heating the
inside of the house. There is no attic or other volume with high
enough temp to raise the inside of the house temp. Show some
calulations and explain your assumptions please.

"CBHvac" wrote in message ...
Learn what a manual J and T are, and latent heat is included...and yes..it
happens...

Hell..it was 65 this morning and my air was on at 75 and the air kicked
on.....it happens...but then, you learn that after years in the biz, and a
few dozen courses in thermal dynamics..storage....and such...

"L. Borne" wrote in message
om...
Am I the only one who thinks this is not normal, other than
LickyDucky? His house has no attic - just A/C rooms. The entire
house is cooled to 78 and it is 58 outside? Any heat they can create
should be going to the big heat sink outside. How does the house heat
back up to 79 to make the A/C kick back on? Where is the big heat
source? A fridge and couple of people can't create that much heat. Of
course, eventually those sources and all the other heat sources will
cause the A/C to kick back on sometime depending on insulation. But
it should not be very frequent. Is the A/C running long, or just a
little. Could it be off 90% of the night and is just coincidence it
is running when you wake?

In my experience with A/C in South Louisiana and Florida, all houses
I've lived in, (all with non A/C attics), did not have the air running
when the thermostat was set at 78 and the outside temp was below 65 -
aproximately.

As has been mentioned, check for a humidity control.

If the A/C is coming on and off, then it is probably working. To
check, just take the temp of the air coming out of a register as
another poster suggested. It should be at least 15-20 F cooler than
the return air. Also, see if water is dripping from the coils? It is
usually routed outside or to a drain.

Another problem which is not common is the placement of the
thermostat. It could be near a heat source, or have a vent blowing
right on it, causing the A/C to shut down too early.






"LuckyDucky" wrote in message
...
We have moved into a house that has central AC. We've never had or used
central AC before but it's very humid here in the South so we've set the
thermostat at 78 degrees to dehumidify the house.

I'm baffled as to why the AC is running in the morning even when the
outdoor
temperature is significantly cooler. This morning, for example, it was
58
degrees outdoors and the indoor temperature was 78 degrees with the AC
running. The only source of heat that I can think of is from the
refrigerator. The hot water heater is in the basement.

I understand why a house requires cooling during the day even when it
cooler
outdoors but I'm totally clueless as to why the house would need AC in
the
early morning after the house has been cooling down for over 10 hours.
I'm
especially baffled because yesterday it was mostly cloudy and cool.

"L. Borne" wrote in message
om...
I've had a few courses in Thermodynamics when I got my aerospace
engineering degree, and use thermo often. However, you don't need
more than common sense to know that if the entire volume of the house
is 78 and the outside air temp is 58, then something is heating the
inside of the house. There is no attic or other volume with high
enough temp to raise the inside of the house temp. Show some
calulations and explain your assumptions please.


I disagree. What about the thermal mass (latent heat) of the furnishings,
appliances, etc. They were at 78 when the temperature dropped to 58.
Between them is a layer of insulation. Fact is, the insulation works both
ways.

Heat your oven with a turkey cooking at 350 degrees. Turn off the oven.
Does it immediately reach equilibrium with the ambient temperature of the
kitchen?
Ed

http://pages.cthome.net/edhome

I understand about thermal mass and I agree with you on that. My
question is - where is the thermal mass? Is it the bricks? What heat
sources are there - water heaters inside, etc.

Obviously, if the system is working correctly and it is coming on all
night, then something is adding heat to the house. This I can't
dispute. And possibly the nights are not 58F long enough to deplete
the latent heat inside the walls, bricks, etc.

If it were 58 for a long enough time, the heat would disipate outside
faster than on the inside where it is 78, only because of the higher
gradient. This depends on where the mass is in comparison to the
insulation, of course. But one would think that over an 8 hour period
of outside temps being 58, and inside temp stable at 78, the thermal
mass of the house would be at or below 78 by morning.

"CBHvac" wrote in message ...
Your degree wont do you a thing, if you cant understand thermal mass...
All the calculations you need, are in Manual J and T...understand your U and
V values, and you got it made...
They are NOT assumptions, and anyone in the HVAC field, with more than 3
weeks in can stand by the simple statement...

Your degree aint worth the paper its printed on if you cant understand
thermal mass...how about transferance?

Have you ever looked at what the average computer system adds to load? How
about a water heater indoors? TV? Refrigerator?
It all adds up, add some solar gain to that...and bingo...you got a heat
bank....

BTW, for giggles and grins today, I checked outdoor temp at 6am, and killed
the AC last night so it would not cool down the home..

It was 71F outside, 89F inside...the unit was cut off at midnight lst
night...now...where in hell did that extra heat come from? I mean...its only
about 3400SF.....brick..AHHHH....there is part of it..brick homes tend to
hold more heat, and while part of that heat radiates back outside, some is
transfered indoors as well..





"L. Borne" wrote in message
om...
I've had a few courses in Thermodynamics when I got my aerospace
engineering degree, and use thermo often. However, you don't need
more than common sense to know that if the entire volume of the house
is 78 and the outside air temp is 58, then something is heating the
inside of the house. There is no attic or other volume with high
enough temp to raise the inside of the house temp. Show some
calulations and explain your assumptions please.

"CBHvac" wrote in message
...
Learn what a manual J and T are, and latent heat is included...and
yes..it
happens...

Hell..it was 65 this morning and my air was on at 75 and the air kicked
on.....it happens...but then, you learn that after years in the biz, and
a
few dozen courses in thermal dynamics..storage....and such...

"L. Borne" wrote in message
om...
Am I the only one who thinks this is not normal, other than
LickyDucky? His house has no attic - just A/C rooms. The entire
house is cooled to 78 and it is 58 outside? Any heat they can create
should be going to the big heat sink outside. How does the house heat
back up to 79 to make the A/C kick back on? Where is the big heat
source? A fridge and couple of people can't create that much heat. Of
course, eventually those sources and all the other heat sources will
cause the A/C to kick back on sometime depending on insulation. But
it should not be very frequent. Is the A/C running long, or just a
little. Could it be off 90% of the night and is just coincidence it
is running when you wake?

In my experience with A/C in South Louisiana and Florida, all houses
I've lived in, (all with non A/C attics), did not have the air running
when the thermostat was set at 78 and the outside temp was below 65 -
aproximately.

As has been mentioned, check for a humidity control.

If the A/C is coming on and off, then it is probably working. To
check, just take the temp of the air coming out of a register as
another poster suggested. It should be at least 15-20 F cooler than
the return air. Also, see if water is dripping from the coils? It is
usually routed outside or to a drain.

Another problem which is not common is the placement of the
thermostat. It could be near a heat source, or have a vent blowing
right on it, causing the A/C to shut down too early.






"LuckyDucky" wrote in message
...
We have moved into a house that has central AC. We've never had or
used
central AC before but it's very humid here in the South so we've set
the
thermostat at 78 degrees to dehumidify the house.

I'm baffled as to why the AC is running in the morning even when the
outdoor
temperature is significantly cooler. This morning, for example, it
was
58
degrees outdoors and the indoor temperature was 78 degrees with the
AC
running. The only source of heat that I can think of is from the
refrigerator. The hot water heater is in the basement.

I understand why a house requires cooling during the day even when
it
cooler
outdoors but I'm totally clueless as to why the house would need AC
in
the
early morning after the house has been cooling down for over 10
hours.
I'm
especially baffled because yesterday it was mostly cloudy and cool.

"Trent©" wrote:

snip


By morning? There IS no 8 hour period. For an 8 hour period, you
MIGHT be correct.

Lately, the low temperature in the morning has been around 61° in my
area...and that's usually around 6 a.m. By 8 a.m., its climbing
again...to the high 80's.

For *you* in *your* area, there is no 8 hour cooling period. In my
situation in the mountains, the sun sets at around 7pm (no sunlight strikes
the house) and the sun rises at about 8am (the time at which sun first
strikes the house). That's about 13 hours of cooling time at this time of
the year (mid-July).

Where *you* live, the temperature is in the high 80's by 8am. Where *I*
live, the temperature doesn't get into the low 80's until about noon and
rarely goes above 86 during the day. You gotta love the mountains.

As a reminder of what I've stated in my previous posts, the days that I've
been mentioning where the A/C has been kicking in the morning is when the
outdoor temperature has been about 58 degrees and the weather the *PREVIOUS*
day has not been sunny or hot.

Another reminder: The only heat producing item on the floor with the
thermostat is the refrigerator. No lights, computer, TV, electronics,
humans or animals. Nothing. We spend most of our time in the finished
walk-out basement where it's cooler and more spacious.



And the absorption rate of many materials is not the same as its
release rate, i.e., if it takes a material 4 hours to save up a
certain amount of heat, it may take twice that long to release that
heat.