hvacrmedic wrote:

The furnaces made today are riddled with problems with short-
lived heat exchangers, sensors and electronic controllers.

Have a look at this site for an example of a poorly-designed
secondary heat exchanger:

http://furnaceclaims.com/

It's generally accepted within pro hvac circles that there are
many new components, ideas and manufacturing techniques cropping
up in furnaces over the past few years that don't have the
benefit of years of field longevity and durability testing.

No it isn't generally accepted. What you're referring to isn't
unsolved problems, what it's called is "planned obsolescence".

When you're designing for planned obsolescence (as you unflatteringly
suggest the HVAC industry is doing) you sometimes overshoot your goal
and create something with a much shorter lifespan than was intended.
Again I point to this as an example:

http://furnaceclaims.com/

The hvac industry is a relative late-comer to that game, thats
all.

And being a "late-comer" to the business of designing for planned
obsolescence, they are getting it wrong in some cases.

Which is a result of coming up with "new components, ideas and
manufacturing techniques over the past few years that don't have the
benefit of years of field longevity and durability testing."

All in all, it doesn't say much for your profession when you are so
quick to advise a home-owner spend $4k on a new furnace when-ever a
$150 motor or $350 controller board burns up (or when a home-owner is
considering improving the efficiency of an existing furnace) -
especially when you admit that new furnace designs are intended to be
inferior to older models.