Oil furnace acid buildup

LIBOB

Check your stack temp. If its below 400 condensation rains down

tom davis

oil furnance acid buildup

I have an oil furnace installed in 2002. In December of 2004 had a flue liner installed--it's a five foot run of 6 in out of the furnace, converting to a twenty-two foot run of 5 inch up the chimney. It was installed inside the existing 7 inch liner. Problem is we are getting major buildups of hyddrochloric and sulfuric acid on the outside of the flue pipe--seems to be leaking through the seams. We cleaned completely, replaced bottom run of pipe, but it's back--and the last deposits showed up in August in major amounts. Also getting some copper deposits. Pulled cap on bottom of the flue pipe, and can see rust on inside for several feet. The installer does not do many oil installations, and is baffled. Says the furnace is running correctly. Any ideas what is causing the problem and what can be done to correct it?

massrookie

acid rain

Yes, stack temp is probably too low, unit may have been downfired from the manufacter's specs.Done that myself , learned my lesson!

Eddy

Don't forget

to subtract the room temp your furnace stack is in from the furnace stack temp for a true reading. Is your furnace short cycling? When an installer checks out a furnace, it has to run at least 15 minutes before any tests are done. If your furnace short cycles (light load, oversized,etc.) it will not reach a hot enough stack temp to run properly.

tom davis

Not the stack temperature

The problem does not seem to be the stack temperature. Measured at 543 degrees with furnace at 82.1 efficiency. One thing that is curious is that the deposits were dripping down in August--very hot outside, no furnace running. Have a five inch liner inside an older 7 inch flue pipe. Pipe passes through five feet of unheated attic. Now where the pipe exits the roof, the space between the 7 inch flue and the 5 inch liner is not enclosed. Possible that's creating a downdraft?

Jim Davis_7

Summer Acid

Had a homeowner that had two oil heat exchangers eat up in 3 years from same problem. Found out that in the summer the chimney way bringing in make-up air for the house. The humidity and rain from outdoors re-wetted the residue left in the chimney and converted back to acid. Pulled back into the heat exchanger and ate it up.