Re: Condensing heat exchanger,outside the box?

Reposting Gunsmoke's <[EMAIL PROTECTED]> query:

>I understand the principle behind the hi efficiency furnace (home use) where
>they capture the last 10-15% of heat from the exhaust, but I have seen
>nowhere on the net and in discussion with furnace installation tech types
>that someone has added an extracting system in the exhaust portion of
>a mid-range efficiency one.
>
>That seems bizzare that something could not be cobbled up to do externally
>what the exchanger does inside the box.
>
>The secondary condenser seems to be just a manufactured chamber that is
>installed, independant of the primary exchanger, inside the unit, so why
>could this not be done after the flue?
>
>Anyone had any experience with this sort of thing?
>
>Ray

Nick