On 18 Jul 2006 06:52:30 -0700, email@example.com wrote:
True, but not sure how much effect this would have on the equation
generating monthly electric bill. Probably not over $5.00 on the
worst month of the year.
Here is some info from the manufacturer of a small AC unit showing
increased wattage due to temp differences:
80 outside air 420 watts
95 outside air 510 watts
110 outside air 540 watts
That shows a significant increase in wattage used when the ambient
temp is higher. Certaintly not intuitive for the general
population, but good hvac guys know this and use an amp meter to
Thanks for everyone sharing their ideas.
I'm no refrigeration guy, but have had a tinge of thermodynamics in my
background. With that, it makes no sense to me that the outside
temperature wouldn't be an issue. The compressor is doing work,
effectively moving BTUs from inside to outside The gas in the outside
condenser is being force to condense. This will be more difficult if
the outside ambient--and therefore condenser--temperature is higher.
The higher the outside temp, the higher the condenser coil temp and
therefore its pressure (I THINK this to be true; there may be something
about the system that says otherwise). Some people put evaporative
cooler nets (wet) around the outside condenser to lower the temps at
the condenser coil and thus improve efficiency. (That's not an option
in humid climates or places where water is at a premium.)
obvious that if the heat sink is at a higher temperature, the spread
between inside and outside temps is greater and therefore the system
has to put in more energy (work harder) to keep the BTUs flowing at the
I forgot one thing I meant to mention. I used to feel that it must be
hard to get an electronic oscillator to start oscillating, and that
eventually it would get tired doing so. Yet I've had tube and
transistor radios and tv that run for hours (or in one case, weeks, on
end, and they never seemed to get tired.
I think I thought it was hard to start them, because I wouldn't want
to oscilate. And that when they started it was sort of like a fluke
(even though, if the device wasn't broken, it always happened. Later
I learned how the circuit works and it didnt' seem amazing anymore.
When you leave the AC on, it has to work harder to keep the house cool
(versus keep the house warm). This uses more electricity.
However, if the recovery time is very long, it might be more important
to keep cool, compared to the energy saving. Since you describe it
"struggling", I'd leave it on. I'd also call a HVAC company to clean
and service the unit. Might be running very inefficently.
Christopher A. Young
You can\'t shout down a troll.
I had a unit that ran almost constantly even with a setback thermo. It
got so bad that if more than two people were in the house (i.e.
grandkids came over), we had to go escape to the mall to get cool. AC
bill more than doubled. Time for a new unit.
Now in spite of at least 50% increase in electricity rates, house stays
at a reasonable temp and AC bill is staying close to the peak before the
old unit got REALLY bad.
I saved about 25 percent of my summer electric bill when I used set
back during the day. That's a huge savings when you are talking
about $400 electric bills.
It started when I bought a digital thermostat that allowed me to
easily control my AC.
We like 74 for sleeping, 78 up until bedtime and 86 setback when we
are not home.
Huge savings. Don't listen to those that say otherwise. They are
lying thru their teeth.
The only other advice I can offer is that it takes about 45 minutes
to make the house livable, so use your digital thermostat to start
cooling 45 minutes before you get home from work.
On Mon, 17 Jul 2006 20:04:18 -0400, "Walter Cohen"
Much the same here. My thermostat is set for 83 on the second floor
with a comfort setting of 80. About a half hour before I get home from
work the thermostat switches to the comfort setting. Seeing as how heat
rises that means the ground floor is quite cool yet the up stairs is
quite comfy at bedtime.
The scroll compressor I had installed years ago has paid for itself many
times over. Runs steady but doesn't have the high draw of standard
Yes. And wouldn't it be nice if the builders these days would put in a
vapor barrier that was worth more than the ink to print the words, so
that the moisture in the house wouldn't rise so much even when no one
That piece of kraft paper on the face of the horribly outdated R13
insulation batt is about as good a vapor barrier as is a kitchen
It's 110 outside, and 90+% of the new homes hereabouts still have only
the R13 in the walls, improperly installed. Homebuyers don't
understand, so builders don't care, so we are stuck..
With myself, if it is going to be a very hot day, I'll leave my A/C on all
day. If a mild day, then I'll leave it off.
On mild days, I can come home and turn on the A/C and it will cool down the
house in not too much time. On really hot days, the A/C takes forever to
cool down the house.
Or depending on if I will be away all day and not return until 10:00 PM,
then I will leave it off. Then when I get home, I can open the doors/windows
and cool the house down quickly.
Coincidentally, I saw this article in teh paper on Thursday. The
information indirrectly from SRP, an Arizona power producer:
"Turning your unit off in the morning when you leave the house and then
waiting until you return at night to turn it back on will save you the
most money. The problem is that not only will the air in your house
have a chance to heat up, but the furniture, carpet, walls, etc. will
aso heat up. With all this heat, it will take your air conditioner
longer to bring the temperature back down to a comfortable level.
"The continuous operation of the units is actually very efficient.
Without all the starts and stops of a typical cycling unit, you're able
to run the system at its peak efficiency. However, setting the
thermostat at 85 will aso save you money (perhaps not as much as
turning the unit off), while not taking as long to recool your house.
Both options work; it's just a matter of how much discomfort you're
willing to put up with."
Sounds good to me!....
The question omitted whether better = feeling
more comfortable or better = cheaper. If you can
read your electricity meter, you can try both methods,
record meters for similar sample days, and see how
elec. consumption compares.
Although you could probably argue that for any duration greater than a few
hours, either criteria could be met by using a setback thermostat and adjust the
restart time to allow for sufficient cooldown.
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