more fun with air conditioning

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How would the house get from 70 F to 105 F in 8 hours on a 100 F day? Assuming it could (which would save lots of AC energy), and assuming it had resonable insulation, it would have very little thermal mass, so the AC could cool it back to 70 F very quickly.

The setback would still save energy, unless the AC becomes a lot less efficient (has a lower COP) with a higher indoor-outdoor temp diff.
A 1500 ft^2 house with 300 Btu/h-F of thermal conductance could warm from 70 F to 105 F in 8 hours on a 110 F day if RC = -8/(ln((105-110)/(70-105) = 4.1 hours, which makes C = 4.1x300 = 1200 Btu/F, not much. A 36K Btu/h AC might cool the house from 105 to 70 F in (105-70)1200/36K = 1.2 hours. Keeping the house 70 F for 8 hours would require 8(110-70)300/36K = 2.7 hours of AC operation... 1.2/2.7 is a 55% energy savings.
Nick
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This is Turtle.
This all looks good on paper but in the real world with a over sized hvac system as you say a 3 ton on 1,200 sq. ft. house. A properly sized hvac system will have a 1.5 or maybe 2 ton at most on the 1,200 sq, ft. house. 3 ton 36K btu rating system when properly sized will never be on a 1,200 sq. ft. house.
Now you say the 3 ton 36K btu rating is used in your calculation here. All hvac system are rated at 95Outdoor temperature and when the ambiant goes above the 95F level your BTU rating falls a good bit to maybe 31K or 33K btu's at 105F outdoor temperature.
Now with all your calculations that the hvac system is perfectly tuned and all coil are clean and serviced regularly. There was some research done in California on systems being properly charged with freon, Clean coils, and running at what they should be putting out. More than half was not operating at what they should have been and was not putting out the BTU rating stated by the manufactor. A lot of the system checked was running at about 70% of what they should be putting out.
Now to you have a big ass 3 ton hvac system on 1,200 sq. ft. house. I personally have a 2,250 sq. ft. home and cool it with a 3.5 ton 14 seer system. I have let my cooling system be off for being gone for about 8 to 10 hours and on a 105F day. My house inside went up to about 98f inside and when i turn on my perfectly tuned system on. It took 3.5 hours to pull the house back to 72 F. The first 2 hours you can not stay in there for it being too hot. Now if i would install a over sized hvac system and have a 5 ton or so. It would not be but a hour or so to get back down to 72F inside but I would have to deal with high humitity in the house and will have to run my system at lower temperature than 72F or maybe down to 65F to get the water vapor out of the house. With a 90%RH a house at 60F will feel very warm inside. With a 10%RH and 95F inside the house will feel very cold. If you don't properly size the system you will have a nitemare with %RH to deal with.
Now here is one that will never fit with your calculation on the cooling of the house. All properly designed and sized hvac systems are designed and installed to have a 90% run time which are designed to be run all the time and not turn them off. On a properly sized / designed hvac system if you started at 100F inside temperature could easily have a 8 hour run time to get it cool enough to be called cool enough to live in it. So if it is designed correctly your theory is out the window. If you have a oversized system you could maybe somewhere near the recovery time needed to get the house back down in temperature, but with no humitity removial like it should be.
Now you had said a house inside with no air on will not go up to 100F+ with in 8 hours -- out in the direct sun light, 105F outdoors, Roof area temperatures running about 190F with the direct sun light on it, house with the average R-19 rating on it, and most all houses are not air tight. In 8 hour, I would be surprized to not see it 100F.
Now one last point here. Your calculation will be for the air inside the house and not for the metal , cloth couches , Rugs / carpet, and furniture which will hold and release heat over the next 4 to 8 hours and you will have to remove this extra heat held by these items as the next 8 hours of operation time goes.
Nick i live in the real world and you must live in the Paper world.
TURTLE
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snipped-for-privacy@ece.villanova.edu wrote:

Nick if you packed more sand in your ass you wouldn't fall over as much.
Just how often do you call criminals over so you get your reaming?
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Dear Bill,
I am not indifferent to the depravity of your cravings.
May God have mercy on your soul.
Nick
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There seems to have developed an ant-intellectual movement on the hvac newsgroups lately.
It's like the dummy's want revenge for something, poor schooling, tired of feeling stupid, whatever, but it's a shameful thing this, all the dummy's united behind PJM who himself doesn't seem to be ageing very well, anyway, the poor soul.

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Don, perhaps I could help you, boy. Maybe I could teach you something slightly technical, something that you could then make your own kind of original remarks on. Perhaps that'd make you feel a little better, being able to participate in these technical forums appropriately applying a little newly learned technical thought.
We should try, it might be quite therapeutic, you wouldn't feel so out of place here needing to side with idiots just because they have numbers and are so willing to accept you as one of their own.
wrote:

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From a condescending prick such as yourself? Don't you have a bottle to visit?
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You have an obsession with drink, Bill, that's not healthy.
wrote:

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It is to Nick, and a few others mind you, that I'm referring.
Nick calls us criminals in good humour. You only get offended because on top of being a complete technical loser yourself, you find it patronising that Nick expresses frustration that you duck right under that humour. Quite simply, you've lost it, you've taken yourself so seriously for so long that you've completely lost the plot.

I might be assuming here, but I would imagine that the only reason you attack Nick for the said patronising is because Paul leads you by example. I've known you on the net for a while, Don, you're not quite an individual, you're a follower, I just wish you'd have higher standards when it came to roll models.
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lot of milligan followers here
and why follow the unemployed dude, who, like an ol woman, has a life revolving around cats
makes not a lot of sense

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Don i am a citizen of both Canada and USA and have always had a job, and have never seen the likes of the whiners on alt.hvac in my travels
why do resi guys - which i could train a border collie to do- whine so much
maybe i would too, if was not smart enough to rise above resi havc

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Just because you can't do good residential work doesn't give you the right to bad mouth those that do.
Picking your ass and carrying a tool pouch while you walk around rooftops checking belts doesn't make you smarter. It just goes to show your employer knows what your limitations are.
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Er, I think there's some confusion here. Um, actually, the way it is, both Shaun and Paul have lives, okay. But it's not the same with jobs, you see, when it comes to employment, Shaun is employed, Paul is UNEMPLOYED. I just thought I should say so because it occurred to me that if your intentions were noble, that you wanted to help someone here, you might redirect the, perhaps disguised, benevolence in Paul's direction, to be specific I suggesting that perhaps you'd like to assist Paul in finding a job. You know, like finding someone that would employ him.
I hope this helps. Helps us all. Please god!
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Marc O'Brien wrote:

Marc, do you have any idea how much money Paul made last year? I have a VAGUE idea, and I can tell you it was NOT an unemployment check. He's got more in the bank than most people here make in a year, and is not limited by some guy cutting him a check every week.
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vicki, if u keep being nice to pjm - u may get him to didle yor cats too
skank

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Sorry, Vicki, you're having another ADD attack :)
It's not money I'm talking about, it's mental health.
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Marc O'Brien wrote:

Marc, you're not an authority on that subject...
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None the less, I still can't help being concerned.
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Thank you , Don, if at least it is an attempt by you to defy the stereotypical pot/kettle dupe-think.
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Individualism is not easily interchangeable with loneliness, and neither would togetherness be with, say, tribalism, or groupthink :)
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