DK wrote:
On 13 Jun 2006 10:21:14 -0700, "RAJ" wrote:

I guess the best way is to just get the estimat first, then say you'll
sign it only if they do the load calculation. The estimate will
probably be overpriced anyway, so might as well get something extra out
of it.

Chris Hill wrote:
On 12 Jun 2006 15:02:54 -0700, "RAJ" wrote:

He just asked me if the existing system cooled properly. Is this
acceptable?
How would a different sized system effect the existing ductwork though?

If you bought a higher efficiency system, you may need larger ducts
because I believe they need to push more air. That's what I've read
anyway. Don't feel bad, last time I had mine replaced I called three
people and none did a load calc. Next time I think I'll offer to pay
for the estimate if they'll do one and show their work.

Load Calcs are usually not necessary. Within 5 miles of me, there
are 10,000 homes built by the same 3 builders, each using 5 building
plans. Everyone in the hvac business knows exactly what size unit
these 5 plans require.

Very good info right there. In fact all the HVAC companies that have
given me estimates on my new estimate (except the one guy) all sized
furnaces in the same BTU range based on square footage of the house and
existing duct work. These guys know what these homes are like and what
it takes to heat/cool them. Yes, they could spend 30 minutes or more
doing a load calc but unless they know EXACTLY how the house is built
(wall/window R rating, etc), that information may be innacurate...as
the saying goes "garbage in..garbage out".

The only load calcs necessary are the 7 custom built 7 bedroom homes
that get built each year.

Do all these homes have exactly the same size units for the same
plan?
- No, of course not. Joe and his wife like to run their thermostat
at 60 degrees year around, even in 105 degree spells. Theirs is a 5
ton system while their friends have a 3 1/2 ton system.

All it takes is a brain and talking to your neighbor., not a load
calc - that will probably be inaccurate anyway.