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Discussion Starter #1
Yes yes, i know. I'll get a hvac load calc , but just looking for guesstamits!

1950s ranch, 1000 sq ft main level, and basement that is getting finished which is 85% Below Grade.

OLD single pane wooden windows, MAYBE an r-11 in the walls ( 2" thick or so....if that " maybe 3" of insulation in the attic that is falling apart.

Summer temps can reach 100+ degrees, typically in the 80s-90s all summer long here in central NJ, humidty can get very very high.


I had a buddy reccomend to me that I go with a 3 ton unit? Though... Alot of the " rule of thumbs " i see are 500 sq ft per ton.... so that works out as:

2 tons per main level
&
go half a ton for the basement since below grade ?
or
give the basement 1 ton?

Should i just assume 3 ton to be safe with my old ineffectient drafty home?

THanks
 

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Wal Mart has a special on PCs. :laughing:

Sorry, just jerking your chain.

No good guesses can be made over the internet.
 

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A very rough rule of thumb is about 1 ton per 500 square feet. Lot of other factors come to play mind you. I would get the installer to do a load calc of course, but if you're shopping I'd just look at 2-4 ton units just to see the prices, don't buy anything till a true calc is done.
 

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Discussion Starter #6
A very rough rule of thumb is about 1 ton per 500 square feet. Lot of other factors come to play mind you.

I figure that... 500 sq ft per ton is for a drafty old house right?

Should a 80% below grade basement that is rougly 1000 sq ft be counted as 500/500 = 2 tons... or since it's below grade only one ton? or half ? what is the GENERAL rule of thumb with that?
 

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Discussion Starter #7
Success! Found my girlfriends old PC laptop, i downloaded the HVAC-CALC 4.0 software and enterened in alll my information.

Im just waiting for the registration code email so that it'll actually display my results, went and paid the 50 bucks, the program seems to work pretty good actually.
 

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Its a pretty easy program to use. Don't fudge the numbers and enter "safe" temps or insulation values. You'll be surprized how much A/C you don't need.
 

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Insulation is cheap,less then $300 for our house which is the same size. Bet a ton and a half will be close if you put R45+ in the attic and caulked those air leaks.
 

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Discussion Starter #10 (Edited)
Got my report!

2.5 tons, it was 2 tons before I added my porch that we never used cause it was always too damn hot. So 2.5 tons should suffice now.

for those on the fence about purchasing this program, just go for it. Def. worth the 50 bucks.

 

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You fudged the summer outdoor design temp. You'll end up with high humidity.
 

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Discussion Starter #12 (Edited)
You fudged the summer outdoor design temp. You'll end up with high humidity.
I realized that and corrected back to defaults. Puts me lil bit below 2.5 tons.

But, today I spoke to my neighbor who has the same house as me, same age. Same layout, same sun. He has 2.5 ton unit and said the unit def has a hard time making temputure in the summer. He had it pro installed 5-7 years ago and serviced last year. He said he'd go 3 ton next time around. Just something I should consider I suppuse
 

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Probably more like his duct work is under sized, then his unit. My own will run for 6 hours non stop when we have our 98° days here, then shut off for 10 minutes or so, and then run for another 4 to 6 hours.

On the hot days, an A/C should run for long long periods of time.
 
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