using anthrocite and wood in the brunco 150 warm air furnace

[francessca]

Hello, Need some help before I accidentally burn the house down. We decided to get anthracite coal this year to complement our wood burning. To make a very long story short yesterday the furnace after burning wood all day suddenly got so hot that it actually sucked the return air duct in. The new chimney appeared to be on fire and smoke kept "puffing out" from around the stove door and air vent. We purchased anthracite coal this year for the obvious long lasting heating effects but really I do not think we understand its potential. This is our habit, Seasoned dry wood starts the day usually anthracite coal is "black" on top without embers. We run the wood fire for about 20minutes or so door slightly open then close it. The day is fine, mid afternoon put some more wood on the fire catches quickly then about 45minutes or so there is a horrible "swishing sound" then smoke billows out from the door and air vent. The new chimney pipe gets fire engine red, the chimney smokes. Is it because of the anthracite that we lay at night to sustain the warmth has heated back up? We have had the chimney guy, who is the best buy the way, come out twice to check for clogging and look at the system. Everything is OK. I believe it is because of let over anthracite, along with the wood it just "bakes inside" then explodes with too much heat and not enough air. The vent is open the pole blower is constantly running and the flue is wide open. I feel we are not saving money and actually are at risk for burning the 160 yr old house down. Can someone suggest anthracite/wood combination or some sort of burn schedule?
Thank You, Francessca

 

[begreen]

I don't have a wood furnace, but this sounds like a very large case of back-puffing. Here is what it sounds like is happening. I'm not sure if it is related to the coal use.

The fire bed is hot, a large load of fresh wood is put on the very hot coal bed. This wood is heated up by the hot coals and the wood starts appearing to char. Air is closed off too much which effectively stops the flame around the wood. However, the wood is continuing to heat up and the highly combustible wood gases start to build up in the firebox. This continues for a period of time until finally a flame erupts from the wood. At that point the wood gas is ignited violently and explosively.

The error I think is closing the air down too quickly and perhaps not letting the coal bed burn down enough before adding a fresh load of wood. Leave enough air to be sure the wood is burning and until the wood has thoroughly charred. Then don't choke it down so much that there is virtually no air going to the fire. Secondary air should continue to burn off the remaining gases.

However, before burning again. The entire system should be professionally inspected. Based on the description, it is possible that the last explosion has done very serious damage to the furnace. It may be no longer safe to burn wood in. The return air ducting system should be totally isolated from the firebox. This may have been compromised by the explosion.

 

[francessca]

Thank you BeGreen,
I totally cleaned out the firebox of all coals hot and cold. I started just a small wood fire. It has been running fine. The neighbors stopped by and practically said the same thing you did. I have not been letting enough air into the fire box, the heat gets trapped and then backs up. I am hesitant to use the anthracite. In reading the materials on the Brunco 150 it states that only "bituminous stove size coal" can be used. I believe it is from August of 1984. In any case I believe that using the anthracite in a older model stove is not wise. If I am wrong please correct me. We are new at this. Thankfully our wood supply is plentiful. From the landmark neighbors observations we have enough split wood for a few years. We have been at the farm house since 2005. We just got the chimney relined. We always burned the bituminous coal and wood together with no problems. The chimney man practacally has a mug with his name on it we have called him so many times this winter. Again thank you for advice.
Francessca

 

[reaperman]

To make a very long story short yesterday the furnace after burning wood all day suddenly got so hot that it actually sucked the return air duct in.

I doubt the cold air return duct was sucked in. What most likely happened is the back plate of the stove expanded (temporarily warped) and with the air duct shroud sitting tight against the back of the stove, got smashed in somewhat. Giving it the sucked in appearance. The back plate of the furnace most likely retained its original shape again after cooling. Or it may be slightly warped, which isn't all that uncommon with a large flat plate of steel without any supports midway in the structure. Not saying your instance isn't reason for concern, but the backs of a wood furnace will warp under normal circumstances. But not to necessairly to the extent of crushing the return air duct.

My extent of burning coal is left at the BBQ pit. Sorry.

 

[webbie]

Hard coal is not usually used with any sort of forced draft combustion.
I suspect you are correct in the reading of the manual - only wood - and the mention of stove sized soft coal is mostly marketing-speak. If the unit does not have shaker grates, etc. then it is unlikely it is designed for coal. Stick with wood - that is my advice.