AC/Unit how big to go?

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I have approximately a 4,000 sqft loft and not sure what size AC/ Furnace Unit I will need. Just trying to get a general idea. I was looking at the following and not sure if it will be able to handle the size of the room.
Goodman Air Conditioner/Furnace Package Unit
GOODMAN Model: GPG13360901AB
13 SEER (cooling) Cooling capacity: 35,400 BTU 80% AFUE (heating) 208 / 230 Volts 60 Hz 1 Phase
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In other discussions like this, people have said the Goodman equipment is "contractor grade", which is the same comment I got from the people who inspected my home before purchase. The vague definition is "sorta kinda good enough, but look at other brands".
As far as the size, a competent contractor will survey the space and make a recommendation based on more factors than just square footage. Another factor would be the number and sizes of windows, for instance. You should consult a contractor.
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On Thu, 05 Jul 2007 14:37:13 +0000, Deejay wrote:

Figure you heat load out first
http://www.heatload.com /
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Deejay wrote:

Why don't you get an extimate by a competent pro. Up here, rule of thumb for cooling need is 1 ton(12,000BTU) per 600 sqf. I am no expert but looks like you need bigger one.
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My cousin is a roughneck and likes his home kept at 65 and he wants it to reach that temp very quick, even in 110 degree weather.
The 'experts' measured the house and checked the insulation and then told him that the manual whatever showed that he required a 2 ton (24,000 btu) system.
He ended up with a free 5 ton (60,000 btu) system that has kept him very happy. The 'expert' hvac guy was not very happy, though.
.
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Thanks for all the replies. I did have one guy come by and his estimate was nuts, so I was trying to get a rough idea before I called more. I think I will need bigger than the one I listed almost double from what I have calculated.

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I see the truth comes out.
You can have it done cheap or you can pay to have it done right the first time.
I guaranty that you won't like the cheap price after you've had many problems with a system that sacrifices your comfort!
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The truth comes out give me a break. The guy gave me a very rough no calculations estimate of 25 grand, so yeah I'm going to ask questions. So don't jump to conclusions.

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4000 sq ft
He might be right on target. Get a couple more quotes and find out.
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That's great if you like that "cave clammy" feeling. It will be a cold house that still has all the humidity since the oversized unit won't run long enough to pull the humidity out. That may work fine in Arizona but here in Florida it will make it "rain" in your house as the humidity condenses on things..
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I would have used a 3 ton if the "experts" said to use a 2 ton. Having lived in Las Vegas for 15 years, I learned early on that too many "experts" and contractors use the one ton per ~400 sq ft rule, and you end up with an a/c unit too small to cool your house when the temp tops 115 (which is does for weeks on end in July and August in Vegas). I replaced my 3 ton unit with a 4 ton unit, and I was in a/c heaven! However, Vegas is quite dry and quite hot, so we don't need much dehumidifying action - we need extra cooling.
My office needs a 5000 btu a/c according to btu/sq foot charts. A 5000 btu a/c runs and runs and runs during the peak of the day, it doesn't cool that well. I now have a 6000 btu unit in the window sill The extra 20% is all it takes to make the difference between sitting here sweating during the heat of the day, and enjoying a nice cool office.
Anyone else care to comment on whether you go with the recommend size, or upsize 20% or so? IANAE, and my limited experiences are certainly not representative of a/c installs in general.
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Ook wrote:

Why? A competent estimator performing a manual J calculation will give the proper size to use.
Having lived

Unfortunately a BTU/square foot chart is only an extremely course guide and isn't really accurate enough to properly select equipment.
it doesn't cool that

Comments inline.
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Because I've spent too many years living in houses with a/c units that were sized according to the house size, and most of them ineadequate. When it hit 110+ outside, we sweltered inside because the a/c just couldn't handle the load. I've had several of my units inspected by repairmen, and all of them told me that the unit was working fine but just wasn't big enough for the house. I had a 1200 sq ft house in Vegas, and a 3 ton a/c. It didn't cool worth squat when the temp exceeded about 105. A contractor told me to replace it with a 3 ton unit. I told him that the current 3 ton unit was fine mechanically, but would not cool when it got too hot, and then he suggested that because it's hotter in Vegas I might need a bigger unit. Well, duh, why don't they do that in the first place? There is a big difference between the size of the a/c unit need to cool a house in 90 degree humid weather, and 118 degree arid weather.
I wonder if the problem is that the contractors use the smallest unit they can get away with, instead of one that will cool the house even when the weather hits 118? IOW, a competent estimator would indeed give the right size to use, but those that build houses like to cut costs when they can, including using small a/c units?

Agreed. A couple of computers, other electrical equipment, a souther exposure, etc. can make big differences in the size of the a/c you need.
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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote

Wonder no more. Builders use as cheap as they can get away with.
The manual J is a very good method of determining the size AC you need, but, it is dependent on proper input. If you design for a 20 degree differential, but want a 30 degree differential, it is not going to work.
What works for me so far, is not to live in a place where the temperature reaches 118 degrees.
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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

That's the difference between a COMPETENT HVAC technician and a hack.
One knows that you sized the unit based on the "design temperature" for the area in which it gets installed!
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Ook wrote:

You just answered your own question. The calculations can't be correct when the correct design conditions aren't used.
You get similar results in an area where heating is the predominant issue. If the builder is trying to cheap out they use a higher outside low temperature with the result being if there is a sustained cold snap the inside design temperature cannot be reached.
There is a big

Sure, and manual J accounts for that. But if the right conditions aren't used then the calculations are useless.

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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

Just another couple of pennies from a Las Vegan ......
I'm waiting as I type for a company to come install a compressor in one of my vacation rentals. Seems like the morons renting it have been having problems for a couple of weeks, "but the temperature was bearable." The house has a five and a four ton unit. I can't say 100% sure that it wouldn't have gone out anyway, so I can't charge them. Grrrrrrrrrrr.
Anyway, I always heard that ......... go with a bigger unit, and then it doesn't have to work as hard. I know that this, too, has its logical limitations, as you would not want to put a ten ton unit where you need three. But I do consider putting an extra ton on there to be a reasonable thing to do.
We're replacing this compressor with another five, as the house has nine tons for 2800 sf. And yes, the units don't run that much of the time and it doesn't take long to cool it down. Plus, for a few months a year, two swamp coolers blow plenty of cool air.
Things people can do, but don't, include adding shades and awnings, installing window tint, stopping up holes, having someone go into the attic and retape all the places that have come loose or weren't taped in the first place, closing the doors when you go outside, having the unit serviced once a year, clearing leaves and crud from around air conditioner, not setting the unit at 47 degrees and leaving for ten hours so it will be cool when you return, and about eighteen other logical things that many people consider to be incomprehensible.
Supposed to be 116 here today. Wonder if it will make it.
Steve
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Ahhh, Las Vegas, home sweet home. 116 this early in July? Niiicceee. I have fond memories of painting the eaves of my house in early August when it was 118 outside. I had no choice, as the house was selling and I had to get it done. I thought I was going to die up on that roof....
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"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

On the good side, the paint dries so fast when you're painting the eaves, if you drip some, it just bounces off the concrete.
We're 98% moved to Utah, and are just waiting for the houses here to sell.
I also have lots of fond memories of Las Vegas. Lately, it's just turned into a crowded cesspool.
I liked it better when "The Boys" ran things.
Steve
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I moved there in 1984, and left at the end of the year 2000. When I moved there, there was no Green Valley, and US95 dead ended at the spaghetti bowl. Lake Mead Drive (not to be confused with Lake Mead Blvd in NLV) went from the old part of Henderson all the way to I-15 with only one traffic light, and there was a couple of miles of empty desert along Boulder Highway between Vegas and Henderson. There was also an empty mile or two of Las Vegas Blvd at Nellis AFB. You could actually drive across the dam, and the tours took you down the looong elevator to the bottom platform. When I left, the road to Lake Mead had a toll station, the city was complete from Vegas all they way along Boulder Highway to Henderson, and Green Valley stretched from I-15 to Water Street, civilization stretched all the way to the air base and beyond, traffic was insane, and it was beginning to get very crowded. Real Estate had not yet exploded upwards, and I sold my house for $99,500. Today that house is worth about $250,000. I walked away $150,000 - all I had to do was stay there for five more years <cries>.
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