more fun with air conditioning

In regards to the recent posting I saw about running the a/c or opening the windows, I would like to list several statements that people have made to me about air conditioning. The location is Texas, where the temperature is about 75 F at night and 100 F at the hottest part of the day.

  1. Keeping the a/c cooling the house all day uses less electricity than turning it off and then back on in the evening or when you return from a vacation.

  1. Running the a/c a few degrees colder at night cools the big cement slab that the house is built on, and thus saves electricity during the day (the a/c is set back to normal living temperature during the day).

2b. If the temperature inside the house reaches 78 F at 10 AM on both days with the a/c set colder the previous night, and also when it was just set normally the previous night, then that proves setting it colder made no difference.

  1. The a/c uses less current at night ( you measure it with an ammeter as it is running ).

  2. The a/c uses less current if you spray the outside unit with the garden hose and then measure it with the ammeter.

  1. Shading the outside unit (compressor and condenser) does not reduce electricity costs [Assume shade does not block air flow].

  2. If you have high ceilings and ceiling fans, it is more energy efficient to leave the fans running at low speed all the time to pull down hot air and get it to circulate through the a/c system.

  1. It isn't worthwhile to check on the amount of Freon (or whatever) that is in the system -- all that matters is measuring the temperature of the cold air coming out (say 62 F) and the outside temperature or maybe the attic temperature.

--Jeff

Reply to
J Jensen
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Hmmm, if the air going into the heat exchanger is 25 degrees cooler (100-75), what happens to compressor efficiency and compressor hp requirements?

Essentially ditto for #3.

There are companies selling swamp cooler precoolers for AC heat exchangers.

Easy enough to prove or disprove. Just watch your meter spin and spray down the AC.

Reply to
jimp
1 no How dumb, you are saying cooling it when you are on vacation is cheaper than not cooling it 2 no Dumb again 2b exact exterior temp , solar load, wind, humidity have been maintained in a lab or your dumb again 3 no , unless voltage is higher at night, which it often is. 4 Hard water , mineral buildup 6 Question is openended 7 Hacks do a lot of stupid things, just ask Daves Heating or I can listen to you.
Reply to
m Ransley

Maybe, it really depends on many many factors. It would be best to measure the specific application.

See above, it might.

Big if. If it does it really means your measurements/test is not valid. College Physics 101 will tell you that if your test is accurate and all factors are considered, there must be a difference, even if it is small. Soft of the butterfly effect.

I believe that is generally true, assuming it is cooler at night.

Same as above, but you may end up damaging your condenser unit.

This is an example of inadequate measurement. There is a difference but it is so small that it is difficult to measure. See 2b.

Only if it is you goal to cool the ceiling.

Worthwhile for what?

Reply to
Joseph Meehan

False.

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False.

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False. Many, many variables in this equation.

Depends. Compressor current consumption can vary with the load.

See above.

It depends.

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Fans don't cool rooms, they cool people (due to the evaporative cooling effect on skin). To save energy, turn fans off when you leave the room.

False. There are many factors that influene the measured temperatures besides the refrigerant charge..

Reply to
Travis Jordan

This is Turtle.

You got too many Question here and I will answer just the first 2 .

Answer to 1 ) If you turn a hvac system off less than 8 hours. It will cost you more money to recool the house from a very high temperature to the lower temperature than just moving up to a higher temperature on the thermostat. If your going to be gone more than 8 hours move the thermostat to about 85ºF or so and turn it back down when you get back home. If your going to be gone for 24 hours or more like on vacation. move the thermostat to the highest setting of about 95ºF and keep the house below 95ºF because refrigerator , Freezers, and Wine Coolers are not designed to run in temperatures above 95ºF. Most or a lot of Refrigerator & Freezers will stop working at 100ºF or above. If you read the installation instruction when you bought the refrigerator or freezer it tells you to not run the appliance in ambiant above 95ºF. Also do not run it in Ambiants of below 40ºF.

Answer to 2) and 2B) .

2) Hog wash.

2B) You found the Hog wash answer was the answer.

TURTLE

Reply to
TURTLE

Part of the answer this has to do with where in Texas you live. If you live in the Houston area, you would probably want to leave it on at all times, if nothing else to prevent a build up of humidity in your home. If you live in a less humid part of the state, this is not as much of a consideration.

Realistically, you have little hope of cooling down a large cement slab, except if you maintain a constant temperature in your home.

It anything, this simply reveals you need a larger air conditioner unit since your current one is unable to maintain the temperature within acceptable tollerances.

I personally have not found this to be the case, either in upstate New York or here in New England. The current drawn by the compressor in an air conditioner barely reflect changes in temperature conditions.

I'd assume that you are joking here.

Shading the condensor unit will improve air conditining performance, but will have only small impact on electricity costs.

This depend on how interested you are in air conditioning your ceilings. Most people couldn't give a hoot.

If the temperature differential between the intake air and the outlet air temperature are operating within specificationd, there is no need to measure the freon pressures.

Harry C.

Reply to
Harry Conover

This has to be some of the purist BS I have read lately.

~kjpro~

Reply to
~KJPRO~

And your comment to his #7 is just as asinine!!

#1 It shows you know little about refrigeration.

#2 That you are a HACK, if you really are in the trade.

#3 That you need to learn more about HVAC systems.

~kjpro~

Reply to
~KJPRO~

Dave probably sent that information to him....you know Dave....full of shit and thinks hes correct.... But...But...its beercan cold doncha know?

Reply to
CBHVAC

That is about what I thought -- the slab really doesn't change temerature appreciably unless you really made the house really cold and held it that way for a long time, which would cetainly not be saving electricity! And if the a/c kicks on at the same time in the morning with or without "cooling" the slab all night, then the rest of the day it is going to run just the same as always.

[snip]

--Jeff

Reply to
J Jensen

I never do turn it entirely off, but that is probably a good point about the effect on other applicances...

[snip]
Reply to
J Jensen

Yeah, as I said in another reply, I think the electric motor would always take the same current when running, but just run for a shorter period of time at night.

No joke. The same person said this as #3 about the current at night and #2 about cooling the slab.

It runs multiple times per hour here (especially the afternoon) and the metal gets very hot in the sun. I tend to think that the savings in shading it must be significant over the length of the summer.

--Jeff

[snip]
Reply to
J Jensen

This was what an a/c technician told me when I called him out to the house with the specific request to check if any Freon had leaked out of the system over the years, or if it was still operating at 100%. He would not do it, although he did check some other things. On the bright side, he did encourage me to sign up for yearly maintenance by his company... :)

--Jeff

Reply to
J Jensen

It seems to me that it would clearly be best to let it get hot in the house if no one is there during the day and just run the a/c hard to cool it down in the early evening. The only issue is that the a/c is then doing a lot of work when the outside temperature is still near its hottest. I am told by someone that this caused the unit to run and run for hours continuously, but my suspicion is that that was due to a lack of freon or some other malfunction (it was a small house!).

[snip]

I am glad that everyone seems to agree that running all the fans and cooling all the air in the house is a bad idea, but, believe it or not, it was proposed by a home efficiency expert to came out to the house several years ago. (I wasn't home at the time so I didn't question him on why he said that).

--JEff

Reply to
J Jensen

If designed properly, an AC system WILL run continuously on the hottest (outdoor design temperature) days in order to maintain the desired indoor (design temperature). Obviously, if the home has heated up beyond the indoor design temperature then it will take the system a while to cool it back down.

Reply to
Travis Jordan

When the equipment is in good condition and properly sized it may run for long times under this situation. That is normal. A larger system would run for less time, but not be as efficient under most situations. I used a lot of conditional statements because there are so many variables that just measuring the results are usually the easiest way to answer the question.

Reply to
Joseph Meehan

and spray

Would the current go down, or the cold being delivered go up?

Bob

Reply to
Bob

And like the previous thread, I treat this posting as a troll. The list is ALL BS,, the responses here and before mostly ill informed Urban Myth and ANY discussion just a waste of bandwidth,,and time.

happy?

BTZ

Reply to
bitzah

READ and BELIEVE..there is no such THING as COLD........... mkay !? Understand that and you will understand W H Y *_you_* never apply ANY condensing medium change to ANY working system...EVER !

BTZ

Reply to
bitzah

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