by mannytheseacow » Mon Dec 08, 2014 2:28 pm
Last week I started having some issues with smokeback up from the feed again. It was really frustrating. It was about the same time that Freedom_Lives posted about his plug. I pulled the exhaust out expecting to find a pile of black dustbunnies.... nothing. So I started trouble shooting the system.
Luckily, I have a direct vent to the chimney which bypasses the bench so I started there. Open the port: no smoke. Close the port: smoke. Must be in the bench, Right? I pulled out all the cleanouts, checked the plenum, just a little fly ash hanging out in there. I knew there was no problem with the core or the riser because the port was working. The other diagnostic was that my barrel was running super hot... like 800* and giving off a ton of heat. Hmmm..... what changed?
So I started running through what was happening. The only thing that really changed was that I had gotten into a section of slippery elm in my wood pile.
A while back Matt posted a link to a firewood page that listed all the different species and their corresponding BTUs. This was awesome, Matt, by the way. I frequently reference this page. But silly me, I have been treating all these BTUs the same.
So, over the last several days or week I have been playing with different wood species. Slippery elm, as it turns out, is kind of lower on the BTU scale for what I have in my wood pile. Much lower than red elm. One load of slippery elm in my feed will burn up in about 20-22 minutes. But in that time, it will pump out a tremendous amount of heat, getting my lower living space up in excess of 80*+ (with an outside temp of 25-30*F). Now, take a load of black walnut- it will burn for about 70-80 minutes, and run my barrel at about 400-450*. Black cherry will burn a little hotter, 450-500* range with a shorter burn time of around 40-50 minutes. Good old red oak, hickory, and red elm all perform similarly, with 500-600* barrel temps and a full feed generating about a 60-80 minute burn schedule (though the red elm will burn slightly hotter and shorter, but the difference in loads of the same species varies about as much as different species depending on the size of the wood being loaded).
Anyway, what's my point? BTUs aren't just BTUs. This is good info if you have a lot of different wood to pick from. When I'm going to be gone for a long day I'll run black walnut; slow and low. When I come home to a cold house or need heat quick, or for an easy starting fire on a damp morning, load some slippery elm. Mix and match what you need for the conditions.
"Knowledge is power. Arm yourself."