Just after I moved into my (used) home, I had the AC unit cleaned & checked
over by a company I've been happy with for 22 years. It got a clean bill of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very hot
day (92 outside today), the system runs almost constantly to keep the house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still curious:
For a given house, and a particular AC unit, is there usually a point where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

It could be low on freon or your coil could be dirty, it worked last
year you say, I would call a pro. Can you get to see your air handler
coil I would start there. You say your attic is insulated, but to what
standard or R value, accepted codes are outdated with presint energy
prices.

"JoeSpareBedroom" wrote in message
...
I'm finding that on a very hot day (92 outside today), the system runs
almost constantly to keep the house at 76. If I set it at 77, it cycles on
for an hour, off for two, and the house is comfortable. I don't NEED that
extra degree, but I'm still curious: For a given house, and a particular
AC unit, is there usually a point where it just won't do more?

Yes. In most cases, the design is for a 20 degree temperature drop fron the
outside temperature. If that was the case, you should be good to about 72
degrees. OTOH, it may have been designed for a 15 degree drop.


Or, does this mean that the previous owners didn't
have the right unit installed?

Depends on your definition of "right". There may be some problem that is
starting to show, such as a refrigerant leak. filter getting blocked, dirty
condenser coil, etc. To go from a 2 hour cycle to running near constant for
only 1 degree does not seem right. It may pay you to have a tech check it
out now under heavier loads.

On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned & checked
over by a company I've been happy with for 22 years. It got a clean bill of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very hot
day (92 outside today), the system runs almost constantly to keep the house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still curious:
For a given house, and a particular AC unit, is there usually a point where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.

"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




Well, it's actually comfortable at 77-78, especially since I work at home,
so I'm sitting at a desk all day. If you're not up & moving around, 70 can
feel pretty chilly. I supplement the situation with a slow fan in the
office, too, so as the temp creeps up (before the AC comes on), it doesn't
feel stagnant.

I'm just curious, though.

"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




I agree with the others that it is probably properly designed for a little
less performance than you would like on the very hottest days. You can
probably squeeze more out of it by improving insulation or shading high heat
gain areas of the house. Basically the same things you do to save heat.

Shading the A/C unit helps, putting silver mylar (emergency blankets from
the camping store) in the windows to reflect sunlight are a couple
inexpensive things you can do quickly and are reversable if they also turn
out to be cosmetically undesireable.

"PipeDown" wrote in message
ink.net...

"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




I agree with the others that it is probably properly designed for a little
less performance than you would like on the very hottest days. You can
probably squeeze more out of it by improving insulation or shading high
heat gain areas of the house. Basically the same things you do to save
heat.

Shading the A/C unit helps, putting silver mylar (emergency blankets from
the camping store) in the windows to reflect sunlight are a couple
inexpensive things you can do quickly and are reversable if they also turn
out to be cosmetically undesireable.

Fortunately, the AC unit's in the shade for the entire day after about 10:00
AM. I've never understood people who say this isn't a factor.

JoeSpareBedroom wrote:
"PipeDown" wrote in message
ink.net...

"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




I agree with the others that it is probably properly designed for a little
less performance than you would like on the very hottest days. You can
probably squeeze more out of it by improving insulation or shading high
heat gain areas of the house. Basically the same things you do to save
heat.

Shading the A/C unit helps, putting silver mylar (emergency blankets from
the camping store) in the windows to reflect sunlight are a couple
inexpensive things you can do quickly and are reversable if they also turn
out to be cosmetically undesireable.

Fortunately, the AC unit's in the shade for the entire day after about 10:00
AM. I've never understood people who say this isn't a factor.


I agree with Edwin that it sounds like something isn't right. The same
system running under conditons where it can maintain 77 with 1 hour on,
2 hours off, shouldn't go to running continuously when it's set to 76.
But on the other hand, for a system to maintain 77 with it 92 outside
and only run 1/3 of the time sounds like the system at that point must
be running OK, as it's not much of a duty cycle.

wrote in message
ups.com...

JoeSpareBedroom wrote:
"PipeDown" wrote in message
ink.net...

"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean
bill
of
health. This was in September, though, so there was no really good way
to
watch it do its thing for any length of time. I'm finding that on a
very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and
the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners
didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




I agree with the others that it is probably properly designed for a
little
less performance than you would like on the very hottest days. You can
probably squeeze more out of it by improving insulation or shading high
heat gain areas of the house. Basically the same things you do to save
heat.

Shading the A/C unit helps, putting silver mylar (emergency blankets
from
the camping store) in the windows to reflect sunlight are a couple
inexpensive things you can do quickly and are reversable if they also
turn
out to be cosmetically undesireable.

Fortunately, the AC unit's in the shade for the entire day after about
10:00
AM. I've never understood people who say this isn't a factor.


I agree with Edwin that it sounds like something isn't right. The same
system running under conditons where it can maintain 77 with 1 hour on,
2 hours off, shouldn't go to running continuously when it's set to 76.
But on the other hand, for a system to maintain 77 with it 92 outside
and only run 1/3 of the time sounds like the system at that point must
be running OK, as it's not much of a duty cycle.


I'm sure it helps that the house has 3 foot eaves. No sun directly into the
windows until maybe 5:30.

JoeSpareBedroom wrote:
Fortunately, the AC unit's in the shade for the entire
day after about 10:00 AM. I've never understood people
who say this isn't a factor.

===========

There is considerable debate on the topic and there have
been some rather well done, well controlled studies.

Obviously, shade vs direct sun is a factor. The important
question is: "How much of a factor?"

Compute the hourly air flow through the compressor unit
on a very hot day when the unit may be running continually.
Better yet, measure the mean temperature of the air flowing
into the unit over the course of the day. I believe that the
studies have shown that there often is very little difference
in that average air temperature and the average air temp
for a unit in the shade. I would guess that the more the
unit cycles on-off, the more important sun vs shade would
be.

Personally, I'm moving my compressor from the very sunny
east side of the house to the very well shaded north side of
the house when I replace the system. Primarily because
it will be further from my patio, but also because being in the
shade certainly must help some small amount.

Gideon

A simple check. An AC system should have about a 20 degree drop across the
evaporator coil. Just measure the temperature difference of the incoming
and outgoing air of the unit. If it is much different something is wrong.
Since it seldom gets above 100 where I live, the delta T maybe less if the
outside air is approaching 120 as it is now in the west. Good to do this
for your furnace too in the winter. That way you can tell if there is a
problem quickly.

"JoeSpareBedroom" wrote in message
...
Just after I moved into my (used) home, I had the AC unit cleaned &
checked over by a company I've been happy with for 22 years. It got a
clean bill of health. This was in September, though, so there was no
really good way to watch it do its thing for any length of time. I'm
finding that on a very hot day (92 outside today), the system runs almost
constantly to keep the house at 76. If I set it at 77, it cycles on for an
hour, off for two, and the house is comfortable. I don't NEED that extra
degree, but I'm still curious: For a given house, and a particular AC
unit, is there usually a point where it just won't do more? Or, does this
mean that the previous owners didn't have the right unit installed?

By the way, the attic is vented & insulated perfectly.

On Tue, 25 Jul 2006 18:43:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
.. .
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




Well, it's actually comfortable at 77-78, especially since I work at home,
so I'm sitting at a desk all day. If you're not up & moving around, 70 can
feel pretty chilly. I supplement the situation with a slow fan in the
office, too, so as the temp creeps up (before the AC comes on), it doesn't
feel stagnant.

I'm just curious, though.


I added a small high eer window unit to save money and liked it so
much, I mounted it in the wall of the room where I spend most of my
time. Huge savings and Huge comfort factor.

"JimL" wrote in message
news
On Tue, 25 Jul 2006 18:43:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
. ..
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way
to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners
didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




Well, it's actually comfortable at 77-78, especially since I work at home,
so I'm sitting at a desk all day. If you're not up & moving around, 70 can
feel pretty chilly. I supplement the situation with a slow fan in the
office, too, so as the temp creeps up (before the AC comes on), it doesn't
feel stagnant.

I'm just curious, though.


I added a small high eer window unit to save money and liked it so
much, I mounted it in the wall of the room where I spend most of my
time. Huge savings and Huge comfort factor.

What's "eer"?

Measure incoming where? Inside the AC unit's cabinet?

"Jeff" wrote in message
...
A simple check. An AC system should have about a 20 degree drop across the
evaporator coil. Just measure the temperature difference of the incoming
and outgoing air of the unit. If it is much different something is wrong.
Since it seldom gets above 100 where I live, the delta T maybe less if the
outside air is approaching 120 as it is now in the west. Good to do this
for your furnace too in the winter. That way you can tell if there is a
problem quickly.

"JoeSpareBedroom" wrote in message
...
Just after I moved into my (used) home, I had the AC unit cleaned &
checked over by a company I've been happy with for 22 years. It got a
clean bill of health. This was in September, though, so there was no
really good way to watch it do its thing for any length of time. I'm
finding that on a very hot day (92 outside today), the system runs almost
constantly to keep the house at 76. If I set it at 77, it cycles on for
an hour, off for two, and the house is comfortable. I don't NEED that
extra degree, but I'm still curious: For a given house, and a particular
AC unit, is there usually a point where it just won't do more? Or, does
this mean that the previous owners didn't have the right unit installed?

By the way, the attic is vented & insulated perfectly.

m Ransley wrote
It could be low on freon or your coil could be dirty, it worked last
year you say, I would call a pro. Can you get to see your air handler
coil I would start there. You say your attic is insulated, but to what
standard or R value, accepted codes are outdated with presint energy
prices.

And ... insulation is (relatively) useless without good sealing. Else
it just adds a bit of turbulence to the flow-through. Potential inlets
and outlets should all be sealed. Around doors is where I'd look first;
note that near a low point of the house with cooled interior, the flow
might be out.

J

Measure at a vent in the house where the air is entering to return to the AC
unit. Measure outlet air at the nearest outlet to the AC. For example on
my system inlet 78, outlet 59, outside temperature 90.

"JoeSpareBedroom" wrote in message
...
Measure incoming where? Inside the AC unit's cabinet?

"Jeff" wrote in message
...
A simple check. An AC system should have about a 20 degree drop across
the evaporator coil. Just measure the temperature difference of the
incoming and outgoing air of the unit. If it is much different something
is wrong. Since it seldom gets above 100 where I live, the delta T maybe
less if the outside air is approaching 120 as it is now in the west. Good
to do this for your furnace too in the winter. That way you can tell if
there is a problem quickly.

"JoeSpareBedroom" wrote in message
...
Just after I moved into my (used) home, I had the AC unit cleaned &
checked over by a company I've been happy with for 22 years. It got a
clean bill of health. This was in September, though, so there was no
really good way to watch it do its thing for any length of time. I'm
finding that on a very hot day (92 outside today), the system runs
almost constantly to keep the house at 76. If I set it at 77, it cycles
on for an hour, off for two, and the house is comfortable. I don't NEED
that extra degree, but I'm still curious: For a given house, and a
particular AC unit, is there usually a point where it just won't do
more? Or, does this mean that the previous owners didn't have the right
unit installed?

By the way, the attic is vented & insulated perfectly.

"Jeff" wrote in message
...
Measure at a vent in the house where the air is entering to return to the
AC unit. Measure outlet air at the nearest outlet to the AC. For
example on my system inlet 78, outlet 59, outside temperature 90.

What is the thermostat set at?

On Wed, 26 Jul 2006 04:15:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
news
On Tue, 25 Jul 2006 18:43:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way
to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners
didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




Well, it's actually comfortable at 77-78, especially since I work at home,
so I'm sitting at a desk all day. If you're not up & moving around, 70 can
feel pretty chilly. I supplement the situation with a slow fan in the
office, too, so as the temp creeps up (before the AC comes on), it doesn't
feel stagnant.

I'm just curious, though.


I added a small high eer window unit to save money and liked it so
much, I mounted it in the wall of the room where I spend most of my
time. Huge savings and Huge comfort factor.

What's "eer"?


SEER is used on Central Units and EER is used on window units, but
they measure 'Energy Efficiency Ratio'.
Lowes has some units that are 10.8 EER and use less electricity for
the same amount of cooling as a 9.8 EER unit.

"JimL" wrote in message
...
On Wed, 26 Jul 2006 04:15:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
news
On Tue, 25 Jul 2006 18:43:42 GMT, "JoeSpareBedroom"
wrote:


"JimL" wrote in message
m...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean
bill
of
health. This was in September, though, so there was no really good way
to
watch it do its thing for any length of time. I'm finding that on a
very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and
the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners
didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.

Sound like your system is designed perfectly.

The downside is that it can't quite maintain on the hottest days.

The upside is that it keeps the house dry and comfortable with
minimum energy usage.




Well, it's actually comfortable at 77-78, especially since I work at
home,
so I'm sitting at a desk all day. If you're not up & moving around, 70
can
feel pretty chilly. I supplement the situation with a slow fan in the
office, too, so as the temp creeps up (before the AC comes on), it
doesn't
feel stagnant.

I'm just curious, though.


I added a small high eer window unit to save money and liked it so
much, I mounted it in the wall of the room where I spend most of my
time. Huge savings and Huge comfort factor.

What's "eer"?


SEER is used on Central Units and EER is used on window units, but
they measure 'Energy Efficiency Ratio'.
Lowes has some units that are 10.8 EER and use less electricity for
the same amount of cooling as a 9.8 EER unit.


Thanks!

m Ransley wrote:

It could be low on freon or your coil could be dirty, it worked last
year you say, I would call a pro. Can you get to see your air handler
coil I would start there. You say your attic is insulated, but to what
standard or R value, accepted codes are outdated with presint energy
prices.


Good advice Ransley.
We used to say and think that 15-F below the outside temperature was okay.

It could be that below 77-F sensible temperature that you have an air
infiltration rate with a latent-load (humidity heatload) that consumes a
lot more than the average 30% latent capacity of the evaporator. The
"Combination of Both Sensible & Latent loads," could cause the sensible
air temperature to NOT drop below the shut-off when set at 76-F.

The higher the humidity infiltration load the higher percentage of the
E-Coils sensible capacity is lost to the latent workload!
You may have some negative pressure rooms drawing in these two heatload
sources.

It would appear to me that humidity infiltration could be the factor
that is stalling the sensible temperature drop under that specific set
of conditions.

There are far too many factors to cover here, that could be causing your
system to only handle the heatload at that temperature & humidity load
levels.
Under a specific set of conditions all units will reach a point where
they will stall at a specific TH setting.

http://www.udarrell.com/latent_heat_condensation.html
http://www.udarrell.com/air-conditio...tent-heat.html

--
Air Conditioning's Affordable Path to the "Human Comfort Zone Goal"
http://www.udarrell.com/air-conditio...tent-heat.html
For HVAC Techs:
http://www.udarrell.com/ac-trouble-s...ubcooling.html

On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned & checked
over by a company I've been happy with for 22 years. It got a clean bill of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very hot
day (92 outside today), the system runs almost constantly to keep the house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still curious:
For a given house, and a particular AC unit, is there usually a point where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.


IMHO:

There are other factors with the lenth of operation of your AC unit.

1. How well is your house insulated (your walls)?

2. How tight is your house against drafts?

3. Is your AC Unit in direct Sun?

4. What is "Checked" by your happy company?

5. Have you checked for any blockage around the ouside unit?

6. Is my air filter dirty.

These are just some questions I would ask myself, when trying to
determine the health of an ac unit.

Personally, I purchased a couple dial indicating temperature probes,
and inserted them into the return, and supply of my furnace/AC coil. I
check from time to time for the differencial temp. If you have a
differencial temp, to tell us, we might have better insite. Your AC
might be working very hard, and have an undersized blower unit to cool
your home.

later,

tom @ www.WorkAtHomePlans.com

"Tom The Great" wrote in message
...
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.


IMHO:

There are other factors with the lenth of operation of your AC unit.

1. How well is your house insulated (your walls)?

2. How tight is your house against drafts?

3. Is your AC Unit in direct Sun?

4. What is "Checked" by your happy company?

5. Have you checked for any blockage around the ouside unit?

6. Is my air filter dirty.

These are just some questions I would ask myself, when trying to
determine the health of an ac unit.

Personally, I purchased a couple dial indicating temperature probes,
and inserted them into the return, and supply of my furnace/AC coil. I
check from time to time for the differencial temp. If you have a
differencial temp, to tell us, we might have better insite. Your AC
might be working very hard, and have an undersized blower unit to cool
your home.

later,

tom @ www.WorkAtHomePlans.com



#1: Wall insulation unknown. Built in 1956, upstate NY, so probably some
insulation, but not much. All non-destructive inspection methods known to
man have been attempted, and failed. But, I'll be doing a couple of
plaster-shattering projects soon, and will have a real answer. And, new
siding comes next year, along with the customary outside insulation.

#2: Tight.

#3: AC unit's in sun only for the first 2 hours in the morning. Total shade
after 9:00 AM or so.

#4: "Checked" in this case meant outside unit cleaned, refrigerant level
checked & adjusted (needed very little).

#5: No blockage outside. Very easy to keep clear.

#6: Air filter is clean. Installed badly by previous contractor (along with
a number of other things). It's the accordion type, and it binds badly as it
goes into the duct, so checking it is not as easy as with a flat filter. I
may have the filter system changed.

At the age of this unit, it's probably time to clean the evaporator
coils. I had a similar situation here in north Texas. A 17-year-old
2-ton unit on the west side of the house, SEER 10.
Today it was replaced with a 2.5-ton unit, SEER 13. The old evap coil
was 1/3 blocked with wet dust. The lower 2/3 I had been able to clean
with a can of foaming coil cleaner. It looked clean from the side that
I could access but the far side told a different story.

Coil cleaning is not an annual checkup item and typically runs about
$200+ when done professionally, but it would make a world of
difference if the unit was otherwise sound.

On Sat, 05 Aug 2006 15:47:10 GMT, "JoeSpareBedroom"
wrote:

"Tom The Great" wrote in message
.. .
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.


IMHO:

There are other factors with the lenth of operation of your AC unit.

1. How well is your house insulated (your walls)?

2. How tight is your house against drafts?

3. Is your AC Unit in direct Sun?

4. What is "Checked" by your happy company?

5. Have you checked for any blockage around the ouside unit?

6. Is my air filter dirty.

These are just some questions I would ask myself, when trying to
determine the health of an ac unit.

Personally, I purchased a couple dial indicating temperature probes,
and inserted them into the return, and supply of my furnace/AC coil. I
check from time to time for the differencial temp. If you have a
differencial temp, to tell us, we might have better insite. Your AC
might be working very hard, and have an undersized blower unit to cool
your home.

later,

tom @ www.WorkAtHomePlans.com



#1: Wall insulation unknown. Built in 1956, upstate NY, so probably some
insulation, but not much. All non-destructive inspection methods known to
man have been attempted, and failed. But, I'll be doing a couple of
plaster-shattering projects soon, and will have a real answer. And, new
siding comes next year, along with the customary outside insulation.

#2: Tight.

#3: AC unit's in sun only for the first 2 hours in the morning. Total shade
after 9:00 AM or so.

#4: "Checked" in this case meant outside unit cleaned, refrigerant level
checked & adjusted (needed very little).

#5: No blockage outside. Very easy to keep clear.

#6: Air filter is clean. Installed badly by previous contractor (along with
a number of other things). It's the accordion type, and it binds badly as it
goes into the duct, so checking it is not as easy as with a flat filter. I
may have the filter system changed.


Well....

Since your replies seem to imply the unit is operating as designed (i
forgot to ask about evap coil being check), maybe the unit is
undersized for the house.

Sorry, it sounds like you need a technician on site.

tom

"Tom The Great" wrote in message
...
On Sat, 05 Aug 2006 15:47:10 GMT, "JoeSpareBedroom"
wrote:

"Tom The Great" wrote in message
. ..
On Tue, 25 Jul 2006 16:48:44 GMT, "JoeSpareBedroom"
wrote:

Just after I moved into my (used) home, I had the AC unit cleaned &
checked
over by a company I've been happy with for 22 years. It got a clean bill
of
health. This was in September, though, so there was no really good way
to
watch it do its thing for any length of time. I'm finding that on a very
hot
day (92 outside today), the system runs almost constantly to keep the
house
at 76. If I set it at 77, it cycles on for an hour, off for two, and the
house is comfortable. I don't NEED that extra degree, but I'm still
curious:
For a given house, and a particular AC unit, is there usually a point
where
it just won't do more? Or, does this mean that the previous owners
didn't
have the right unit installed?

By the way, the attic is vented & insulated perfectly.


IMHO:

There are other factors with the lenth of operation of your AC unit.

1. How well is your house insulated (your walls)?

2. How tight is your house against drafts?

3. Is your AC Unit in direct Sun?

4. What is "Checked" by your happy company?

5. Have you checked for any blockage around the ouside unit?

6. Is my air filter dirty.

These are just some questions I would ask myself, when trying to
determine the health of an ac unit.

Personally, I purchased a couple dial indicating temperature probes,
and inserted them into the return, and supply of my furnace/AC coil. I
check from time to time for the differencial temp. If you have a
differencial temp, to tell us, we might have better insite. Your AC
might be working very hard, and have an undersized blower unit to cool
your home.

later,

tom @ www.WorkAtHomePlans.com



#1: Wall insulation unknown. Built in 1956, upstate NY, so probably some
insulation, but not much. All non-destructive inspection methods known to
man have been attempted, and failed. But, I'll be doing a couple of
plaster-shattering projects soon, and will have a real answer. And, new
siding comes next year, along with the customary outside insulation.

#2: Tight.

#3: AC unit's in sun only for the first 2 hours in the morning. Total
shade
after 9:00 AM or so.

#4: "Checked" in this case meant outside unit cleaned, refrigerant level
checked & adjusted (needed very little).

#5: No blockage outside. Very easy to keep clear.

#6: Air filter is clean. Installed badly by previous contractor (along
with
a number of other things). It's the accordion type, and it binds badly as
it
goes into the duct, so checking it is not as easy as with a flat filter. I
may have the filter system changed.


Well....

Since your replies seem to imply the unit is operating as designed (i
forgot to ask about evap coil being check), maybe the unit is
undersized for the house.

Sorry, it sounds like you need a technician on site.

tom

Yeah...I get the same feeling. Luckily, the company I use will send out the
owner to survey the house for a possible replacement, but without a huge
pain in the ass sales pitch. Just "Here's the right unit, call when you're
ready. Doin' any fishin'?" Pleasant people. And, when the furnace needed
service last winter, the tech arrived in sloppy, snow covered shoes, removed
them, and pulled a dry pair out of his tool bag. WTF? Who does that these
days???????????