I took for granted that I would replace the monster of a furnace in the garage, but when I realized I couldn't afford my preferred attractive heating method: hydronic heating from floor and radiators, I started wondering. I read somewhere that people tend to get caught up in nominal specs, like 80% efficiency versus 93%, and also that people often feel their new system is just badly designed.
In my situation, I am using a lot of therms because my windows are single pane and there is no insulation in the walls and ceiling. But I would reduce my heating energy consumption immensely if I addressed these auxiliary issues, rather than the heating source.
So I set out to get some more information about my installed system. It is a Tuck Aire furnace, name tagged Western, from 1959.
- model: CFB 27-120
- BTU/H: 120000
- Bonnet capacity BTU/H: 96000
- serial: 1059
The manufacturer who is still around guesses its efficiency to be between 60 & 70%.
I asked one of the online forums for advise and the suggestion was: "your steady state efficiency is 80%. Your AFUE is more like 50% [AFUE is Annual Fuel Utilization Efficiency, I guess the assumption is that the pilots run all year round]. So, a new induced draft would probably save you 30% plus. A 90% plus, would save that much more. BUT, get a load calc done, so the right size is put in. Doubtful you need that big a furnace."
It is a tough choice. I want to spend my money wisely, but it doesn't seem like my expected future heating consumption really justifies the replacement.
December, 19. 2008: I had the furnace services. It is a tad less noisy but the repair man claimed he couldn't make the noise disappear: the bearings are worn and there are apparently no spare parts to be had. So it will have to be replaced sometime during this remodel
