Normal yes, whether that amount is normal or not I'm not sure. sounds as if it may be a bit excessive for only a few weeks. Over a year period ours accumulates about 1 to 2 inches but that's on a very large exhaust pipe, 18 or 20 inches I think. Excessive fly ash can be caused by too much draft or if you have a lot of fines in the coal or even the coal itself.
I'd monitor it and make sure that it's not accumulating too much. Obviously you don't want it getting to the point where it is blocking the pipe. Deaths due to CO poisining are usually attributed to blocked pipes from fly ash, so you'll want to keep an eye on it. I'd suggest if it gets to the point where the pipe is 1/3 full you should clean it out, otherwise once a year. Also make sure you clean the chimney out, you should have a space below where the exhaust meets the chimney. Most of the fly ash will accumulate at the bottom of the chimney.
Keep in mind that at first it will accumualte quicker in the pipe because there is less space to fill. It may just be that amount is normal for your type of stove. If it's a smaller stove and you're pushing it to the limit where the combustion fan is caonstantly running then yes it would accumualte pretty quick.
Last edited by Richard S.
on Tue Feb 07, 2006 1:57 pm, edited 2 times in total.