Increasing OWB efficiency

[ngzcaz]

  For those that have fan forced air induction in their stoves have there been any advances in retaining heat instead of it being forced out of the chimney when the blower kicks on ? The blower certainly makes for quick heat recovery but it also forces a lot of heart out the chimney.    ;D

[thecfarm]

With mine I can burn dead wood in it. No run away fires. I like the blower system. Allows me to burn wood that I could not control in a stove that has its own draft.
With my Heatmor,I can throw in a paper cup and if the furnace does not cycle,that paper cup will not burn. It will still be there as long as the blowers do not come on.It make be kinda black,but I can still tell it's a cup.I can open the door and the fire looks to be out,it's all black.

[woodmills1]

this year my blower motor died, and as you may or may not know my stove company is out of business.  I was going to experiment with drilling different sized holes in my restrictor plate or making a sliding opening to do away with the blower. 

I stayed with the blower for two reasons.  I found that it is a readily avalaible assembly part as a blower/motor combo and the ease of operation with many different types/quality of wood.

If some green pine goes out ona warm october day due to small demand, I can put one sheet of newsprint and a bunch of rolled flyers and use the propane barbeque lighter to start and just use the blower and it lights.

[leonz]

If you can afford fill your boiler 1/2 full of fire
brick you will have a huge heat sink and a
cleaner burn.

[woodmills1]

wouldn't that cut way down on the heat exchange between the fire and the water?

[barbender]

I've had this thought before with my Heatmor, too. That blower is sure nice for betting green or wet wood burning, not so much when there is a flame shooting 2' out the stack :D I thought it would be slick to have a 2 stage system, with a powered damper that opens first, and if the fire doesn't take off, the blower would kick in. The thinking was as far as I got on it :

[thecfarm]

Probably the reason I never see flames,mine had to travel the full length of the furnace about 50 inches,then I added on 3 sections on to the chimney. I also have 2 blowers because of the size of mine too. That much more of a chance to blow more heat up the stack.  :D

[Ivan49]

I've had this thought before with my Heatmor, too. That blower is sure nice for betting green or wet wood burning, not so much when there is a flame shooting 2' out the stack :D I thought it would be slick to have a 2 stage system, with a powered damper that opens first, and if the fire doesn't take off, the blower would kick in. The thinking was as far as I got on it :

You don't have to worry about cresote that way ;D

[leonz]

wouldn't that cut way down on the heat exchange between the fire and the water?

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NOPE!! I have had my boiler half filled with full size firebrick for three years
now and I wish I had done it 32 years ago!!

Once the boiler gets hot it stays hot and the firebrck becomes a heat sink
keeping the fire hotter and making it burn cleaner.

MY mass of fire brick is 12 by 12 by 36 inches tall and it sits on 12 by 12 inch
piece of channel iron which sits on the frame for coal grates and it has worked
wonders.

I burn short wood as a rule becuase I carry it in five gallon pails and it burns
very hot and clean.

I have to fill the ash pit half full of fire brick to shorten the ash pit and add
more thermal mass to the boiler this year.

I also burn coal and it helps that a lot too.

[NWP]

I've never really had flames out the top of my Heatmor. It doesn't have any extra sections on it. Sometimes when it's dark and there's a good fire going in it if you look real close you can see a little glow coming out of the stack.

[ga jones]

I'd like to see a pic of your fire brick set up leonz. That's a good idea. The heatmor has fire brick in it and sand. To hold the heat. I have added a switch on the blower motor. Separate from the flap. I natural draft dry wood and force draft wet.

[leonz]

I'd like to see a pic of your fire brick set up leonz. That's a good idea. The heatmor has fire brick in it and sand. To hold the heat. I have added a switch on the blower motor. Separate from the flap. I natural draft dry wood and force draft wet.

Greetings and salutations ga jones,


Let me see about getting a picture to up load using
the wide digital camera on saturday or sunday.

I have to let the fire burn down to show the channel
iron sitting in the coal grate frame and.

Is your skidder equiped with an air cooled Duetz engine?

I knew Tree Farmer was using the Duetz engines exclusively
for the longest time and a large air cooled  engine like those
last many many years working on the surface

[ga jones]

No my tree farmer is a 3-53 detroit. My timberjack is a 6bt cummins.

[leonz]

The wife has a fire going now GRR.

ANYWAY:

The boiler is 31 years old, the firebox and water chamber
is made entirely of boiler plate, I do not remember how
thick it is.


NOW;

the firebox is 12 inches wide, 24 inches deep and
48 inches tall.

The water jacket surrounds the sides and the top only
and it has 20 or so gallons in it.

The coal grates are the side to side shaker grates.
I wish they were the rocking grate type though as
I would lose much less coal in the ash pit.


The coal grate frame supports the grates and is
12 inches above the boiler base plate.

The coal grate frame is made from angle iron.


I purchased a piece of channel iron 12 inched wide and 12 inches long.

I placed this piece of channel iron on the coal grate support frameand it is flush with the boiler walls.

Now as to the firebrick

I purchased I think at least fifty full size fire brick
from a large distributor and a local retailer(PAIN IN THE (*&^%)

After experimenting with brick placement I ended up doing
it simply as the boiler was really not wide enough to create
a running bond or  jenga pile.


I laid a layer three bricks flat by the left wall and two bricks narrow
side up along the right boiler wall. Each layer has five bricks in it
with two bricks narrow side up next to the three firebricks laid flat
one behind the other.

I stacked all the fire bricks like this to very bottom edge of the 8 inch
flue opening reducing the volume of the firebox by less than half
creating a heat sink out of the stacked fire bricks.

Iit works well and it also aids in creating  a better
draft in my case as the chimney barely clears the
peak of the house roof.

AS long as the bricks are stacked neatly and from
wall to wall andnear the flue opening it is ready to fire.

It works for me and if the fire goes out the heat stored
in the fire brick rises and aids in maintaining a good
natural draft.

I cut my wood short and split it to very small pieces and a
small hot fire does not smoke very much in my boiler.

Before I had the opportunity to purchase a Sequoyah boiler
with 600 gallon capacity and coal grates rick closed up shop.

I was going to purchase a 2 pallets of fire brick and a piece
of channel iron 12 by 24 and simply stack the firebrick until
I was satisfied I had enough brick in boiler to create
much more thermal mass.   

I think firebrick is stacked 100 bricks to the pallet or was anyway
from the brick makers.

ANY boiler would benefit from this as there is little if any smoke. 

                             

[ga jones]

I will try something similar to your set up. It sounds good to me.

[dave_dj1]

I don't have an outside boiler but I did have an indoor one. That being said, the one I had had an automatic draft door on the bottom that was hooked up to an aqua stat, when water temp dropped, draft opened, when temp was reached draft closed. This worked all well and good for it's intended purpose, if you liked burning a LOT of wood! I started to experiment with the draft door. I ended up threading a stop into the bottom draft tube so I could limit the amount the draft door closed. This made my wood efficiency go up exponentially. Once I did this I used much less wood to heat the same home. The only learning curve was the distance to keep the draft door open depending on how cold or warm it was outside. After a winter of using it this way I knew about how far open it had to be for different temps. The house was a 5 bedroom poorly insulated cape in the north east. With the auto draft I could barely keep a fire over night, once I did away with it It I easily had a nice bed of coals come morning no matter the outside temps.
I would think the same principal would work with an outside unit. I think maintaining a temp is better than letting the water temp drop and come back up under a hot fire. I know this might cramp some of your style and you probably would have to burn dry wood.  Which in my opinion you should anyway but let's not get into that!

[beenthere]

I have similar arrangement on my indoor wood boiler unit.

However, I would sure hesitate propping the draft door open and not able to close tight shut on a boiler unit.

When my water temps get up to just below boiling, I want that draft door closed tight but even residual heat in the hot wood coals will cause the temp to rise a bit after the draft damper is closed. So I set the water temp max at 180° F

I do put some restriction in the air intake when the damper is open, depending on how fast and hot I want the fire to burn. Depends on wind and outside temp.

But have found no need or desire to allow air to the wood when the water temps are high.

I don't find I burn excessive amounts of wood, at least in the 30+ years I've used this boiler.

[thecfarm]

I've had wood stove,indoor boilers,old cook stoves and the OWB that I have now. I would not want to go back to what I use to use. I am very happy with it.

[Corley5]

The solenoid that controls the air shut off on the forced draft motor burned up on my OWB.  After a bit of experimenting I found that a 20 penny spike between the blower cage and the plate that shuts the air off was enough to maintain the water temp and keep the house warm until the new solenoid arrived.  The stove got pretty sticky inside  ;) ;D