From: "Travis Jordan" 
Newsgroups: misc.consumers.house sci.physics alt.home.repair sci.engr.heat-vent-ac
Subject: Re: more fun with air conditioning
Date: Fri, 23 Jul 2004 18:00:24 GMT

J Jensen wrote:
> "Joseph Meehan"  wrote in message
> news:...
>> J Jensen wrote:
>>>>
>>> 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.
>>
>>     Maybe, it really depends on many many factors.  It would be best
>> to measure the specific application.
>>
>
> 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]
>
>>> 6. 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.
>>
>>     Only if it is you goal to cool the ceiling.
>>
>
> 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

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.