DIY intercooler for oil fired furnace

noskralc

Idea:



I have a typical furnace setup - oil burner, forced air. the exhaust pipes from the burner (to the chimney) are extremely hot to the touch when the furnace is on. This is wasted heat!



Could I wire in a relay of sorts off the 24VAC that activates the house fan (or the furnace itself for that matter), to start (turn on) a box fan (or other fan) to blow over the exhaust ductwork? The real solution would be to put a heat exchanger in with a blower, but this would suffice for now. My basement doesn't get that cold, but every bit of heat helps!



Could the 24VAC trip the fan/furnace relay AND a secondary relay as well?

Jamie Hall

Sure it can be done...

but there are a few things to think about.



First, any change to the flue pipe will upset the draught in the furnace; you will need to readjust the burner and any induced/forced draught fans and any barometric dampers.



Second, consider the lining of the chimney, or the material of the exhaust stack.  If you manage to get the flue gas temperature down to near or below condensing (212 F) you will get condensation in the rest of the exhaust and the chimeny or stack.  This condensate is very acid and very corrosive; unless the stack or chimney is built for it, it won't last long.



Third, of course any change to the furnace wiring (even if you do it yourself) will need to be approved by local code -- and your insurance company.

Harvey Ramer

Why don't you build yourself

a nice half round reflective shield. Place it around the flue leaving a 6" air space. Now aim your new radiant heater where you want it to be warm. It won't reach very far, but it also won't cause condensing in your flue.