Coal stove flue pipe rehab

There is plenty to go wrong here, but you can repair it
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kevm14
Posts: 15238
Joined: Wed Oct 23, 2013 10:28 pm

Coal stove flue pipe rehab

Post by kevm14 »

It is a coal stove but I burn wood in it. Would be nice to get a real wood stove some day.

Had a damper issue with the flue. It felt like the damper flap itself slipped on the control axle so it wasn't clear what position it was in. Plus, and it did this before, there was no friction in the damper to stay in a set position. So I decided to pull the elbow and pipe off the stove and check out what went wrong.

The repair was actually simple. I replaced the elbow and flue pipe, bought a new damper (all 6"), drilled two holes, and installed the new damper. Then I re-insulated the chimney flue itself around the pipe. I pulled out all the old fiberglass and used mineral wool which is rated to like 2000F. This way I felt comfortable insulating right up to the pipe. The old stuff had a gap and it's unclear whether that was intended or just happened over time. Home Depot had everything I needed.

I have pics to share. But it went well. The new damper holds its position, and the new insulation feels like I have stopped a nasty draft. Good stuff.

The other good news is I have totally demystified my stove setup. If I were to encounter a deal on a wood stove, I would feel comfortable installing it.

Probably wouldn't be a terrible idea to have this chimney cleaned. Since they do it from the bottom that would require re-doing the pipe/insulation setup but maybe the chimney guy can do a nice job. Otherwise I'll have to do it again which is not hard but awkward to lay back there and everything you touch drops something on your head...
kevm14
Posts: 15238
Joined: Wed Oct 23, 2013 10:28 pm

Re: Coal stove flue pipe rehab

Post by kevm14 »

Lit off the first fire since doing this work yesterday. There was a somewhat alarming amount of smoke that seemed to billow gently from, well, the area where the new pipe and insulation are. That subsided within 5-10 mins and then seemed fine.

It was nice to be able to control the position of the flue damper. I let it warm up a bit before really choking it off but I ended up with the damper in the completely closed position for what I believe was best efficiency. Of course I know from installing the damper that completely closed still leaves at least a 1/2" gap on one side of the flue pipe so it did have flow there. But it did seem to extend the reload cycle even with my crappy wood. I want to say 90 minutes was more typical which is good. Definitely interested to get some more usage on it and see.

Side note, the damper was too hot to touch despite the small heat-shedding spring on the handle. I will need to leave a glove by the stove.
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