RT wrote in message ...
On Wed, 13 Jun 2007 16:03:36 -0500, kjpro @ usenet.com wrote:


"v" wrote in message
...
On Tue, 12 Jun 2007 21:01:56 -0500, someone wrote:


v would probably suggest a 3-ton unit in that example. rolleyes

The contractor can't "cut corners on the formula" because he likely
doesn't have and doesn't know the formula anyway. He just punches the
numbers in to something that he bought and then tries to impress you
with the resultant printout.

I used to do these "by hand" (okay, pocket calculator) back in the
day. Don't confuse precision with accuracy. Garbage in garbage out.
You are better off with someone who can make a reasoned estimate here
and there, than with someone who laboriously inputs precise fractions
but uses the wrong conditions and assumptions because he is just doing
data entry and not understanding principles.


Yeah, well, we don't send out a rookie with a computer to perform a load
calc.

If you'd send someone out that has HVAC knowledge, you would understand
that
a load calc *is* worthwhile.

Might as well install that 5-ton unit, Eh?


Where I come from, rule of thumb for average constructed homes is 1
ton/500 sq ft (8ft ceiling). Of course it's not calculated but I bet
it's close to accurate for the average home where I am.


Where I come from, I do things correctly. That means the client gets a
Manual J to correctly size his or her new system. However, there are hacks
everywhere that use "rules of thumb" for just about everything. Their
clients are unhappy when they receive a quote to fix all the screw-ups.

Do it right, or do it twice. I garranty doing it right the first time is
cheaper in the long run!