"v" wrote in message
...
On Tue, 12 Jun 2007 20:11:54 -0500, someone wrote:


The customer gets a complete print-out of the Manual J and Manual D
calculations that tell exactly what is required. Unless you do the math
and
run the calculations, your doing nothing but guessing.
Do *you* want to base that kind of investment and cash outlay on a guess??

What I'm getting at is, how does one "cut corners on the formulas"
when the contractor is using a commercial spreadsheet package where he
puts in the parameters and the "formulas" are built in. I used to do
these calcs "by hand". I doubt most contractors could, they just use
their computer package and the answer is whatever it says. So what
that they give a copy of the printout to the homeowner. Don't confuse
accuracy with precision.

I used to be able to manually do load calcs, but that was before I had a
computer and the software to do it with more precission, and a bit faster
too.
Without precission, you don't have accuracy.

If a window is 4'-8" by 3'-4" but the contractor figured it as 3 x 5
feet, is it going to matter that he took a shortcut with the formula?

In the grand scheme of things, probably not, or not enough to make a
difference. FWIW, I *DO* use the exact measurements.

So you get an "exact" calc, but the units are not made in that "exact"
size. Then you ask the contractor to use his experience, judgment and
understanding of principles to tell you that you are better off with
the one that is a little undersized even though the one that is a very
little bit oversized is closer to the "exact" figure.

The load calc will tell you what btu capacity you need, and the
manufacturers specs will tell you whats available. Somewhere you have to
come to a happy medium.

I'm not impressed with people who toss around an "exact" figure that
just came out of a computer as if that means the person holding it
knows something.

Nobody asked if you were impressed or not....I just do the very best I know
how to do. so why are you here trying to stir the pot??