I’m trying to develop an energy efficiency program on replacing those really old inefficient furnaces that still seem to stick around. Do you know how to identify ~60% AFUE residential furnaces (these should probably be the old gravity/octopus designs) and to differentiate them from the ~70% AFUE (these would probably have conventional blowers for air distribution, a draft hood, but still have a standing pilot)?
1 For the old furnaces (especially gravity, or “octopus” furnaces), are the efficiency ratings on the name plates, still typically readable?
If so, do you happen to know if the efficiency ratings are in terms of AFUE, combustion efficiency, or thermal efficiency?
If not, the only other way I can think of identifying ~60% efficiency (AFUE) furnaces (and differentiating them from the ~70%-ers), is by checking to see if the furnace is the old gravity type furnace (implies 60% AFUE). The ~70% will typically have draft hoods and a standing pilot light, but will have the conventional blower for air distribution throughout the house. Any comments?
4 Is there an easy way to tell if a furnace is a gravity furnace?