how contractors really size aircon

I like the "front door rule" :-)
http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-289-95/index.htm
Nick
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On 5 Oct 2007 13:00:28 -0400, snipped-for-privacy@ece.villanova.edu wrote:

One of the most telling bits of info is the "reasons for oversizing". The most common reason is because the customer requested it. That suggests to me that in the real world the Manual J and other "correct" ways of sizing are too often giving undersized results and the customers have learned from past experience that they need a bigger unit then the "experts" tell them they need. Almost every place I've lived in has had undersized cooling.
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wrote:

This is done strictly out of ignorance.

This is only because the customer is trying to get the system to do things that its not designed for

Probably not.....a correctly sized system is designed to *MAINTAIN* the average comfort levels at the design conditions....not bring the temp in a 100 degree home down to 70 degrees in 30 minutes. Its not gonna happen.
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Noon-Air wrote:

That's the customer's choice to make. Who are you to say what he should be able to call upon it to do? He's the one paying.

If that's what the customer wants, and he's willing to pay for it, and it's not illegal, then who made YOU king?

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wrote:

things
a
CJT if you had a clue, you would know it's not expected from a system that's correctly sized.
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wrote:

I have had CJT in my killfile for a long time.....He doesn't *want" to understand about manufacture design limitations, or proper sizing. He doesn't care about getting it done right, All he cares about is how cheap can he get it done.
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Noon-Air wrote:

Actually, that's incorrect. But I've found by bitter experience that you do not always get what you pay for where HVAC "professionals" are involved.
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Dont worry. We all know the turd is clueless. Bubba
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kjpro @ usenet.com wrote:

Expected by you, you mean, using a particular definition of "correct."
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wrote:

in
that's
Boy, you could be an English teacher, but you just can't understand plain English. Pretty simple, Shut The Fuck Up ASSHOLE.
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kjpro @ usenet.com wrote:

No. Take your own advice.
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CJT... "correct" is defined by the proper science and calculations according to the requirements by the IBC, IMC, NEC, ASHRAE, and State/local laws, codes and regulations.You seem to think these don't apply to you. Maybe you need to do some homework before trying to stir the pot here.
For the most part, *most* of the regulars in alt.hvac are certified master techs, and contractors. Alt.hvac is *NOT* a place for home owners to come while about paying $100 cause they were too ignorant to change their filters. Thats what alt.home.repair is for.
We are not going to assume the liability of telling you how to fix your jurassic furnace, sight unseen, and without knowing what your abilities and capabilities are. You need to call a local, *COMPETENT*, licensed, insured, professionally trained, HVAC technician to come diagnose and repair or replace your broken air conditioner, heat pump, furnace, and/or boiler.
If you would be so kind, please quit cross posting this junk.
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Noon-Air wrote:

As pointed out in the article that started this thread, many "professionals" don't use those calculations. Are you suggesting they should all be thrown in jail?

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wrote:

You then are obviously clueless. Manual J works this way: "Correct iinfo put in.......Correct info put out" "Garbage in................Garbage out" That is plain and simple. It seems however that you have just been too cheap to either hire a competent home inspector or a competent hvac company when you bought all your homes. Perhaps if you had done it the correct way you would have then had the proper info to negotiate the purchase of all those homes so you could live in a comfortable home. Next time, try and Expert, not an "expert". Bubba
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Ashton Crusher wrote:

A manual J would provide the correct size unit, however, the reason the correct sized unit does not cool to design is because of multiplicity of other factors, that need correcting! http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
Click on the Anchor link: "Specifications VS Reality," = 95% failures of an AC's Major Performance factors: Ductwork - Airflow - Proper Charge, Installation, etc. - udarrell
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Ashton Crusher wrote:

Hmmm, Are you trying to show your fine ignorance? Deal with competent techs from reputable outfits. And educate yourself as well. Quality of work is doing it first time right. Cheap techs, cheap customers will never get quality. You can interchange words cheap and ignorance. As a plain consumer, at least I know this much.
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an interesting read , thanks for the link
snipped-for-privacy@ece.villanova.edu wrote:

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