Efficient use of Air conditioner

[tom]

Can not convince wife about two things. Just want to bring it here for a serious judgement:

1. Use Air conditioner for home at night: Temperature outside = 69F, Temp in home = 81F, Air conditioner trigger set to 75F

method A. With windows being open - My way method B. With windows being closed - Wife's way

Question: which one make house temp drop faster and which one costs less electricity?

1. Use AC for car in a hot summer day Temperature outside = 80F, Temp of a car parked in sun for one hour = very hot, don't know exact temp

After getting into the car Method A: open windows, drive for a moment then close the windows and start AC. - mine Method B: Start AC right away without opening windows. - wife's

Question: which one make car temp drop faster and which one costs less electricity?

Thanks!

-Tom

[micheal]

1 - this depends upon the temperature Vs time profile, A and B are good strategies with certain profiles. you also need the humidity levels/profile, as air that is cooler but has a lot of moister causes the AC to run longer to remove the water. If you have 30% humidity, widows open, 80%, windows closed. Look up latent heat. 2.- Method A. Get that superheated air out (140F) and start with 80F

[Pyriform]

Modified method A: Start the AC at the same time as you open the windows. The system will take a few moments to start producing cool air, so you might as well have it do the pre-cooling in parallel. Won't make much difference to the energy cost, and the total time to a cool car will be less.

After you've closed the windows, set the AC to recirculate for a while until the car has reached a comfortable temperature. Some climate control systems do this automatically.

[DHatheway]

Method A is probably going to be moer efficient in both cases.

So what? The energy and money you save doing it your way would not offset the cost of a divorce. Do it your wife's way whenever she's around.

[greywolf42]

If there is no wind (or no fan blowing the cool air into your house), then neither method A nor method B will cool the house down more quickly. This is because the air return to the AC system is inside the house. The hot air will not get 'blown out' of the house. And there will be minimal air exchange through the windows.

As the wind increases, eventually method A will cool the house down more quickly. However, it will take a good sized wind or big windows to beat the AC. AC units typically cool the air about 20 degrees F. So the air coming out of the AC will be at 61 F (starting with 81 F), regardless of where the thermostat is set.

(Let your wife win on this one.)

If you want to save electricity, buy a window fan.

Method A here will cool the air inside the car faster. But the main source of heat in the car is not the air, but the roof, seats, floor, windows and dashboard. They've all been heated to uncomfortable levels, and the heat capacity of the air is minimal, compared to the rest.

Once the air has been blown out (which will take about 2 seconds), you can safely close the windows.

There is no electricity in a car AC system (except in an electric car)... the AC compressor runs off of an engine belt.

-- greywolf42 ubi dubium ibi libertas {remove planet for return e-mail}

[Brigitte]

So true! Don't waste your time and energy on this trivial crap.

Brigitte

[Joseph Meehan]

There are far too many variables to say one or the other.

I will say the one thing many people miss when they try to figure this out is the very high cost of removing the moisture that comes in from outside.

However I do have an answer. Real time test! Try it both ways several times. See what works best (more comfortable and less run time) Repeat several times on different days. Keep records and let us know the answer. (Local weather may provide degree days so you can adjust for different outside temps to some degree.

Most cars burn gas not electricity. ;-)

Generally I would guess opening the windows for the first quarter mile to exchange the hot inside air, then shutting it up. There have been a number of test that indicate that cars with A/C get better mileage using the A/C than by opening the windows because of all the wind resistance added by the open windows.

[nicksanspam]

Joseph Meehan wrote re:

That's a low cost, unless water vapor condenses inside the house.

Nick

[HeatMan]

It also has to do with air filtration.

[Doug Kanter]

You must be young. You will soon learn that with regard to climate control, women are completely out of their minds. There's simply no point in arguing. If she wants to waste money doing the wrong thing, let her.

In my wing of my office building, there are 3 small offices, one of which is mine. Three separate tenants, in other words. The thermostat is in the office next door. Three women work in that office, ranging in age from 30 to

1. At almost any time of year, I couldn't figure out how to dress comfortably because of the huge temperature swings. It got to the point where I brought in a recording thermometer that I use around the garden. In any 8 hour day, the temp would vary as much as 20 degrees. The ladies thought this was funny. Finally, the landlord put a locked box over the thermostat and set it for 72. The ladies swore the temp was all over the place, so the landlord brought in a digital recording thermometer. (Big office park, well equipped). It showed a temp range of about 2 degrees either side of 72. End of problem.

Just give up.

[JAC]

Depends on what the humidity is outside. If you are brining in cool, dry air, of course the open windows help drop the temperature quicker. If it is humid air, the air conditioner runs more.

What do you mean "which one costs less electricity" in a car? Gas mileage? To this question, I would say who cares? You guys need to find something else to talk about. Just do whatever makes you feel less miserable when you get into the car.

[Dan O.]

That depends on more than just the temperature difference.

How long would opening the window(s) take to make any significant change in the *total* air volume of the house?

How much 'breeze' through the window can you expect? How constant will it be?

Will it be able to vacate hotter air in *all* parts of the house equally or just mostly in the room(s) with the windows?

How humid it is outside and in? Cooler, humid air is sometimes more uncomfortable than warmer, drier air.

If you're not going to get good air movement throughout most of the house (or at least where people will be), I would likely use the a/c. Even if it doesn't drop the temperature fast, it will still make the air more comfortable by dehumidifying it.

The one that uses less power. ie. No a/c.

Well since the a/c in the car doesn't run on electricity, neither.

The answer, is... C.

Method C: Start the a/c right away, open the windows for a block or two, then close them. That will purge most of the extra-hot, stale air from inside the car, vent most residual moisture from the a/c's evaporator (cooling coil) housing and ductwork and get the evaporator coil cooled down so the air you're now keeping inside is right off a already cold cooling coil.

JMO

Dan O.

- Appliance411.com

=Ð~~~~~~

[TURTLE]

This is Turtle.

Reply split in parts

What Price do you set on your Happiness ? That will be the Price you'll pay for having it your way or not choosing Method B.

What Price do you set on having a enjoyful Drive everywhere you may go ? That will be the price you will pay for not choosing Method B.

Now you have a choice here by Choosing Method B and have a enjoyful life or Choosing Method A and Paying the Ultimate Price on Happiness the rest of your life. I even think your going to pay the Ultima price even asking this question.

TURTLE

[TURTLE]

This is Turtle.

Would that filter be for the Shit coming his way also ?

TURTLE

[CBHVAC]

PROBABLY B.

What you say? Simple..opening the windows will remove some of the warm air, but unless you have a whole house fan pulling like hell, you wont be able to use all that cool air out, and you still have latent heat in the walls, floors, ceiling...furniture...etc..

But my queston is....why are you allowing your air in the home to reach 81F? Set your thermostat and forget it...its cheaper that way..

Again...depends. Personally, my personal work van for example, has these neat little vents in the taillights...fire the AC up, open they go, and out goes the hot air.... And even when I was in CA,I didnt worry about that stuff...I just went on with it...

[jmfbahciv]

If it's like my A/C, the compressor won't run because it's already cool (on the outside).

Constantly not listening to the wife will produce a cold atmosphere of other flavors. Comparing costs of electricity alone ignores the long-term costs.

The best use of a house A/C is to use it with a fan. Nobody believes me when I say that I cool my house with a 5000 BTU A/C and two fans.

/BAH

/BAH

Subtract a hundred and four for e-mail.

[BonnieJean]

x-no-archive:yes

Although this is an interesting quesiton, for a novice like me, Turtle hit it on the head. Would you rather be right/in control or happy?

Bonnie

[nicksanspam]

Why latent heat, ie condensation?

Newton was wrong? :-)

Nick

[bitzah]

UR joking..right? best effort in response. Hire a Limo. Take Wife to chuddly kuddly Asian eathouse (aka kai store) Consume best Chili dish..two servings each + 1liter of Shiraz. How does this help? For cool arse.. have Limo driver maintain a constant 55mph (critical) whilst yourselves (collective) park your respective arses out the back window..avoid tunnels and Paparazzi !

cheers

BTz

[bitzah]

or FOS...?

BTZ