Bitter cold last night with temp below 0 and 15 mph winds. Loaded outside boiler with dry hedge and hickory. This morning when I checked stove there were no visible splits but stove was over half full of glowing red coals. Just curious what causes this instead of wood being consumed into ash? Not a problem but curious.
We have this problem with the Ideal Steel Woodstoves. The wood pyrolyzes (sp?) and the stove burns up the gasses from the wood. All that is left are the coals. There needs to be an addition of more air to burn the coals down. I believe it has to do with the burning off of the gasses at a greater rate than the coals are being burned up.
I am in my fourth year with the stove but this was the first time I have seen so many coals after overnight burn. Was chock full of high btu wood. Would that have an impact?
Hickory and hedge are 2 very dense wood which would add to the condition stated above. Less dense wood such as basswood, some pines and maples won't coal quite as much in enclosed chamber and just about not at all in an open fire.
I have posted this before but it bears repeating in this thread. From woodheat.org "Big coal beds are a particular problem with EPA certified non-catalytic stoves because their insulated fireboxes and high temperatures tend to cook out the volatile gases quickly, leaving a big load of charcoal. This isn't much of a problem during moderate weather because the coal bed can do an adequate heating job. But when the weather gets very cold, a coal bed is not enough to heat a house and the big coal bed gets in the way of adding more wood. The solution is to rake the coals towards the primary air inlet, place one log on the pile of coals and burn it fast. The primary air on almost all modern wood stoves is the airwash for the glass, so rake towards the glass door."
I'm glad you re-posted that, oldspark. Osage Orange posted that this is happening in his OWB- do you suppose the same thing is happening inside his boiler?
Very helpful and makes sense. We definitely had colder than normal last night - probably the coldest night since stove was installed due to the wind. In my case I put two smaller splits on the coals and the pile burned down to ash fairly quickly.
I am sure it could be, if his wood is dry and he's running it hard and it's a EPA type boiler, I dont know much about boilers.
Agreed with the fact that you need more combustion air. Some wood furnaces, oddly enough those sold at tractor supply have an under fire air damper (rotary) that allows you to regulate the air for combustion coming up through the ash. Works great once you get a few burns and understand the wood you have etc. My large expensive stove does not have this, so I am forced to pull the coals towards the door each time I fill and generally that takes care of it. Good luck!
Can't help with why it happens - but throw some soft wood on top & run as normal. Those coals will be gone lickety-split!
Another thing to keep in mind is that less than dry wood will tend to give more coals but the type that doesn't give much heat. I'm a bit surprised you have this problem with a boiler though. When we started with the Fireview, the first epa stove we've had, we were perplexed with all the coals once we started burning hard as the temperature fell. After some experimenting, we found that just about the time the fire was down to the coaling stage or just before that point, we open the draft as far as possible. This will hold the stove top temperature steady while the coals burn down. We've had to do that only a few times so far this winter. Sometimes I will also use the poker and rake through the coals to loosen them which helps to burn them down quicker.
My old stove does not do it even with a big load of Oak, its great having a ton of heat and no coaling problem. The Summit was terrible with the coaling problem. The Drolet is much better then the summit, seems like it burns the coals down better and puts out more heat. This was all done with dry wood by the way.
As has already been mentioned, the well-insulated firebox of some stoves/boilers combined with a heap of dense hardwood will lead to coaling like that. I'll only add one thing to what's been said already, raking the coals to the front of the stove and opening up the primary air, with a small spilt or two, will help burn those cold off and give you a good quick burst of heat. I've seen heavy coaling in my stove when I use cherry. And I do the prescription above to remedy it....
Yep, it's been said many times to put a small split on the coals up near the air intakes to burn that down. I had a huge coal bed this am, but loaded 5 splits on top to warm the house. I'm now gonna' need a few hours of using this technique to get rid of all those coals.
Gonna beat the dead horse a little more. LOL Nothing worked with the Summit and the coaling, I would open up the air and put small pieces of wood on the coals and all it did was add to the problem for some reason, the Drolet burns them down quicker and dont even need the small splits so far. My point is (if I have one) even among the EPA stoves there may be some better then others. Edit-been thinking about the Drolet vs the Summit, I think the Summit is much more insulated then the Drolet so that could be part of it.
1-How about not shutting down the primary air so much over night? ie. a hotter overnight fire 2- Does leaving the door open (while you sit by the stove) burn the coals faster? I tried that this morning, but I'm not sure its better. I ended up throwing out a pail of coals.
Not going to work for me as I am running the stove plenty hot the way it is, I dont smolder my stove what so ever and keep the flue temps about 300 or so during the active part of the burn. Not sure about the door thing, not something I would like doing but finding a solution means trying different things.
I'd suggest that firebox insulation is a red-herring. It serves to keep temps up for complete combustion/efficiency. My experience is that for a long-term mid-winter burn, stuffing the firebox and throttling the primary air makes for lots of coals. (Yes, black cherry is especially good at leaving unburnt coals.) If you can tend to the stove every so many hours, you can avoid a mountain of coals and maintain heat output with smaller batches of wood and more primary air.
