Top down fire

[KsWoodsMan]

I'm curious about who else has tried a 'top down fire" or uses it regularly. I've noticed it mentioned once or twice in the last couple of years here but it just never went very far , other than what is it ?

I've mentioned using the method of a TDF a few times with links to different sites. Sites that explain the benefit of starting the fire from the top of the pile instead of the bottom. In the last couple of yeas I have seen it mentioned less than a handfull of times by others but the topic of wood gassification boilers and heaters comes up often. An EPA approved wood space heater has to burn cleanly to be compliant. If a TDF burns clean could it also pass emmisions tests in an older heater ?

I have to admit that I was skeptical about TDF's, at first. In the last few years I have looked into wood gassification. In the 40's Europe was burning wood, chasrcoal and other biomass to power cars, trucks, busses and tractors because of the scarcity of gasoline/diesel for the war effort. They basically ran their car on the 'smoke' from downdraft gassifiers. A TDF works on the same principle as a down draft gassifier without the complexity of additional hardware.

The gasses given off from heated wood is what is burning, not the actual wood itself. By passing the smoke through a bed of glowing charcoal the smoke and tars are broken down far enough that they ignite off and burn easily. The gas from this can be used to power an engine or used for cooking and heating. By lighting the fire from the top the smoke is passed near, through or around the glowing coals. Allowing that there is enough air getting to it there is almost a complete combustion. The warmer, rising air surrounding the glowing coal ensures that there is a continous supply of fresh air to support combustion. This combustion supports the pyrolization of more wood. Complete combustion means no creosote formation inside the stove or flue pipe, more heat from a more efficient burn and fewer trips to load the stove.

Any way back to the question, Who's tried it ? What was your experience ? and who is making use of this method ?

 

[TreeTopFlyer]

Inverted fire

Check out this link:



http://www.wooddoctorfurnace.com/converter.html

Works good when you have a hot bed of coals, no smoke.

But after shut down you have to wait for bed of coals to get hot again to stop the smoke. Other than that it works great.

Martin

 

[jerry wayne]

once

heard about it once on this site.tried it once,never a better way to start another fire IMOA .NUFF SAID:greenchainsaw:

 

[elektrobot]

Top down fires are a snap if your wood is properly seasoned.

 

[dnf0929]

Check out this link...haven't tried it yet as it's been pretty warm in these parts.

http://www.woodheat.org/tips/topdown.htm

 

[aokpops]

been using it for years. glad to hear other people use it . told a few how it works just got the eye roll . never spoke of it again

 

[cityevader]

I just got in from working all day splitting and stacking, and thinking about this top down fire idea, and how trying to search for it here sucks because we can't enter phrases in quotes...instead a bizillion posts with the individual words top or down show up....

Now here it is!!!

That's the second time I thought all day about something and someone beats me to a thread!!!

 

[starter]

I heard about this a few years ago and use it off and on. It is a good way to start a fire cuz you don't have to add fuel as soon. The TDF first fire lasts longer.

It seems to work well but I do notice that the large logs at the bottom don't burn completely. The bottoms of them don't sit on coals so they don't really burn all the way until you move them around when reloading.

There's not much point to the TDF when you already have a bed of coals. Anything will burn on top of that.

 

[AOD]

Ive tried one, it didn't work worth a crap, maybe it works better over a grate or I'm doing it wrong.

 

[Wood Doctor]

Ive tried one, it didn't work worth a crap, maybe it works better over a grate...

That may help it and why that it works so well in my stove. TreeCo's Jotul and my Federal Airtight are perhaps similar stoves in that respect--the grates allow air to pass underneath the fire and vertically so it is never starved for air on startup, once the draft is established.

The large logs below have gaps between them that allow the air passage to the smaller kindling above them. Once that kindling is hot, the coals from the smaller pieces start igniting the large logs and keep them going, dropping between the gaps.

I usually start with two or three logs at the bottom, newspapers and cardboad next, and then top that with five or six small kindling pieces. At first it may seem slow, but it never fails to catch. Once the kindling is exhausted, I add a couple of more larger logs, and after that, she's on her own for quite awhile.

My modified top down method also requires about half as much newspaper and cardboard.

 

[KsWoodsMan]

I don't have that problem at all. Is your wood good and seasoned?

What I like about the top down fire is that once it gets started...even a little bit......it grows into a full fledged fire and does not need fooling with until it's time to reload. The top down starting method also seems to leave the viewing glass cleaner.

If the glass and flue pipe are cleaner the exhaust would tend to be also. Thats part of what prompted me to think that burning a top down in an older OWB might help it to pass EPA guidelines. I was thinking of a variation of a top down in an OWB or non exempt stove, more of a crossdraft or back to front fire.

Ive tried one, it didn't work worth a crap, maybe it works better over a grate or I'm doing it wrong.

No, the grate wont make any difference till you get to the very last of the charcoal. There isnt much to do wrong. It just needs air, Dry seasoned wood works best for burning. A TDF won't make up for deficiencies in the fuel.

Now I know I havent been completely alone doing it this way. I figured there was going to be a mixture of replies, most of them to be from skeptics with the argument that "fire burns up". The first time I seen it tried a friend of mine was trying to get it going with wet wood. Even the old smokey method of burning barely got things started. That was years ago and on just one occasion. It nagged at me till I tried it again with better wood. I was amazed at how evenly it burned the whole time and didnt require being tended. Any additional feeding of the fire once it was started just resulted in smoke.

 

[AOD]

So how exactly does one build a top-down fire? Is it in the way the wood is loaded?

 

[KsWoodsMan]

AOD, I start with bigger pieces on the bottom. The fire will eventually burn down to these. Ontop of these I will put my smaller splits then kindling allowing for airflow from underneath. The tinder goes in the top. I try to make sure that the tinder is between a couple of kindling sized dry pieces. The tinder will burn off catching the kindling below it and beside it. The charcoal from these creates enough heat to finish off the gasses that arent quite burned by the kindling/wood below it. As the fire spreads across the top it will continue to burn off the smoke and will spread down slowly through the stack.

The heat from convection is drawn away from the wood. The smoke carried by the convection gets burned above the glowing charcoal. The radiant heat from the charcoal heats the wood to create 'smoke' or combustable gasses that get burned above the charcoal.

The radiant heat of the coals makes the gasses that burns. The burning gasses provides the radiant heat to warm the outside of the firebox and convection to create draw for the whole process to sustain itself.

My firebox is a North to South configuration. Meaning the small door in the front (South) lets me load 20" wood in there with the cut ends towards me. I actually light a fire in the very back of the stove under the flue pipe. I light it here instead of the front and let the fire burn from the back to the front. It works the same way ( almost ) as a top down. The firebox is a bit over 12" wide. If I feal really industrious I will cut the 16-20" splits in half and lay them sideways in the stove with the fire started in the back. I get more wood in there this way and longer burn times still. It is at the expence of extra time cutting.

When the fire burns down I have a pile of coals in the front that I move aside and clean out some of the ashes . I put in a few pieces in the back move the coals on top of them where the light off the wood underneath and start refilling the stove in whatever configuration I feel like at the moment.

If I end up with unburned log ends I know I pulled wood out of that stack before it's time.. Usually that isnt the case. During the summer we, the kids and I, will have a fire some nights in the back. This is when I am checking wood for usability , they just think it is for grilling or marshmallows for s'mores.

If I come in, the fire is out and the house is cold I will light a small conventional fire in the front to take the chill off quickly. The coals from this will then go in the back to re-stat a fire that will burn for several hours instead of just a few from the same amount of wood. If I use less, keeping my house just as warm, it gives me more to sell. It might only be a cord more but that's a couple hundred dollars when it is all said and done. It is about the same as paying myself to burn it responsibly.

 

[AOD]

Thanks KSWoodsman.

Do you burn over a grate or just over firebricks. My stove just has a plain steel bottom and I would like to line it with firebricks. My old, very small stove had bricks, and I added a small grate to it, after I started using the grate my ash was cut in half, and the ash I had was much finer.

 

[KsWoodsMan]

You are Welcome. There isnt a fire brick , one, in my wood eater. When I clean out ashes I have found it better to leave 1/4 - 1/2 inch layer in the bottom to help direct the heat up to the burning area.

As described, my stove isn't very large. When the day comes that I go to a better stove I figure to have an insulated burn chamber lined with firebrick or refractory cement. Limited time and the rising cost of plate steel has put a dampener on those plans for now.

I did build a grate that kept the wood about 2" off the bottom to make it easiier for ash removal. I dont use it now, it limited the size of pieces that fit through the door and size of the already small firebox. The ashes were finer, I don't recall that there were more or less of them just that, in my firebox, it wasn't as handy as I had hoped it to be. YMMV It just didn't work well for me.

 

[bore_pig]

KS--You say that your topdown fire saves you a cord a year. Isn't this just a starting method? How often do you need to start a fire? My stove has a 3.1 cubic foot box. I lit a fire last nov, and didn't light another until april. Don't know how I could save so much wood.

 

[HARRY BARKER]

KS--You say that your topdown fire saves you a cord a year. Isn't this just a starting method? How often do you need to start a fire? My stove has a 3.1 cubic foot box. I lit a fire last nov, and didn't light another until april. Don't know how I could save so much wood.

same here.

 

[KsWoodsMan]

I guess you both mean this ?

If I use less, keeping my house just as warm, it gives me more to sell. It might only be a cord more (should have been - less used - my apologies) but that's a couple hundred dollars when it is all said and done. It is about the same as paying myself to burn it responsibly.

I don't know for a fact that it is a cord that I save. It could be more OR less. I havent gauged it. My kids are older and more responsible about keeping the doors closed. I am no longer adorned by the presence of "the little lady of the house" stoking up a huge fire with the front door open "because, (she) was cold". Much like when she would turn the thermostat up to 95 "To get it warm in here faster." :eyesroll:

One of my last NG bills in '96 was over $400. Following '96 I could easily go through 4-5 cords hedge, mullberry, oak, hackberry and anything else I could come up with. The last 2-3 years I have practiced the topdown quite a bit more and cut my useage down to 3 - 3 1/2 cords of Hackberry, Mullberry and a little Hedge for part of January. The better wood now mostly gets sold. In late winter I would be scrounging wood to burn after what I had was used up. This winter I have what I will be using brought to the house. I also have some of what I will be selling here too. Even when supplementing with wood in '97 & '98 I still couldn't get enough wood to keep her warm.

I don't have to let the fire go out. I can move the coals/fire from the front to the back, clean out any ashes I see fit and add more wood to the front.

I'm not saying that anyone else should be burning this way. Part of what I asked originally was

If a TDF burns clean could it also pass emmisions tests in an older heater ?

I left that answer up to someone with an OWB or another exempt stove to try. If it made as much heat with fewer trips out in the dead of winter would it be worth the change in how you burn your fires ? To me , it is.

Mostly I was curious about other peoples experiences, I expected to get called on this somehow. That's OK too.

 

[cityevader]

If somebody was home at my house during the day to feed the fire, I'd never have to relight.

As it is, the thing has been out for many hours by the time I get home. Every single night is a re-light. (tiny airtight stove) Would be the same every morning if I didn't throw some large chunks of slightly greener Oak just before bed in order to have coals in the morning.

 

[bore_pig]

After 8-10hrs I still have enough coals for the fire to relight itself.

KS--You talk about raking your coals. I do that to. Saves a TON of wood. No disagreement there! Am I incorrect in thinking that a topdown fire is a method of starting a fire?