I have a contractor who tells me I need 1 CFM per sq ft. That means I need 1980 CFM or 2000 CFM (no model J done)so a 4 TON will not work since 4 TON is 1600 CFM. Is this guy full of it or not. I hear people with 3.5 TON units and 1900 Sq ft in other areas of the country.
If that guy said it is raining outside, go look!!!!
You need a load calc run, not some rule of thumb.
I've got a lot of 3-ton systems on that size house.
"FIGHT CRIME: SHOOT BACK"
Click on the red tab, and pay the 50 bucks and do your own load calc.
Then you'll know what size you really need.
Not knowing where you are in New Mexico, he could be right.
Depending on your house.
I have the software. I calculates 2.5 tons. That is why I am confuse. I am worried I input some data wrong. I am rechecking my measurements now.
What is your outdoor design temp, and what is your indoor design temp.
Manual J doesn't tell you the size of the unit per say, it tells you how many BTU's at your design conditions, then the contractor is suppose to select the size unit that will meet that.
We are not in yur area I do not know factors involved to make a this judement. Thats why you want to have a couple bids.
Talk to the contractor have him show cost of what he is doing.
Maybe another contractor will give you more like a pad for the unit to set on , larger duct, sizes, easy access, a oudoor disconnect sw, digital tstat, emergency cut offs
Sometimes you need alot of air exchange. If this contractor is the one you trust work it out.
You can hang yourself with rules of thumb. They just don't apply to every situation.
I live in New Mexico and at 5200 ft of altitude there are factors that don't follow rules of thumb.
27deg temperature swing
Thinner air transfers temperature 4% per 1000' less than sea level.
Light construction compared to moderate or heavy
If a contractor bids a lot in a development that have similiar homes he probably can wing it.
But like it was said pick up a copy of ACCA Manual J or go to HVAC Calc and they have an offer for a one time load.
I should have played the g'tar on the MTV. MK
You can be anything you want......As long as you don't suck at it.
"I have a contractor who tells me I need 1 CFM per sq ft."
Is this a new rule of thumb for southern states or have I been out of school so long that someone dreamed up a new one?
I personally still like the "how many fingers from across the street?" one.
Beleive or not....I had a contractor tell me that is the way he sizes the duct. If a room has 100sq ft it gets a 6in pipe.
"FIGHT CRIME: SHOOT BACK"