JO's wood boiler

Night shifts at the mill all weekend. Waking up at noon each day and working the chainsaw in the woods until dark. Collecting firewood for season 16/17 (also lot’s of limb wood to feed the rebak chunker :smile:) . Have to take advantage of nice weather. Feeling pretty beat.
Below zero at nights. Relaxing by watching the boiler flame. Enjoy.


Your video says Private…

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Sorry! Chainsaw is my friend - computer not :smile:

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Still private? Should be ok.

Works great now! Beautiful flame.

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Hi, Jo, can you explain how your down flame boiler works?

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My Gosh!! J.O I am finding you to be a building genius. Working on a gasifier, and you already have built a Rebak chunker, and a "swing blade " saw mill. Now we find you have what I imagine is a gasifier boiler. What will we learn about you ( oh and you like to fish)?Tomc

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HI, Don! I’ll try:
Imagine your WK with secondary preheated air added from slots in the restriction. Gases will instantly burst into flames and due to the cylindrical ceramic combustion chamber they swirl both ways, creating an upside down atomic bomb mushroom. Lot’s of turbulence and a clean burn.

The hopper is all inside water mantel and will ofcourse be very tary but heat radiation from hot charcoles, when fuel level gets low, bakes the tar into a hard shiny crust that protects walls from rusting. Hopper holds 150 L 1/2 m logs. It lasts 2-4 hours depending on wood quality.

After combustion the super hot exhaust enters ash deposit/dropbox and than up into 10 heatex tubes. Tubes are easily cleaned occationally from the top hatch. Always only fine white dust.

The boiler manages with only chimney effect, but I’ve added a fan on top of the chimney for easy startup and warm weather. It operates on thermostat (exhaust temp).


Tom! Hold your (sold) horses!

Are the logs stacked vertical or horizontal? Hopper tapered down to restriction? How tall chimney? Very intriguing concept!

WOW really interesting. Dry wood, or green? Hot water heat in the house, shop? What a beast.

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What causes the pull of the gases down through the restriction?TomC

Whooo Big fella!! I’m trying to slow him down, but I do get amazed at what some of you guys accomplish. I on the other hand did not even get out to the shop today and there was no reason. TomC

“The boiler manages with only chimney effect, but I’ve added a fan on top of the chimney for easy startup and warm weather. It operates on thermostat (exhaust temp).”

I’m guessing the chimney draft for the boiler pulls on the gasifier hearth through the gas outlet.

Brian is right. Chimney draft it is. Pulls really good when it is cold outside.

Tom, I’m sure you’ve done your share of hard work beeing a farmer and all. You deserve some armchair time.

Carl, dry wood, the dryer the better. The boiler itself holds very little water (120 L) and reaches 90 C operating temp in 10-15 min. A thermostat will then open and the hot water is piped into a 4000 L (4 m3) storage tank. The tank then supplies house and shop/garage with heat for 2-3 days. A fresh water heatex is fitted into the the top of the tank.

Don, logs are stacked horizontally. If vertical I think fire would climb causing a wildfire in the hopper since primary air is fed from the top (fema style). It does happen sometimes anyway when wood aren’t stacked properly. There will be puffs out the air inlet and a smokey basement.
There is no tapering down to restriction except for built up ash around it. Chimney is 8m from basement floor to the top.


Smoke free when up to operating temperature?

Yes, only condensing steam from the chimney. I’ve put my face over it at full blast. It hardly smells anything.

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Is it a belt drive helper fan so the motor stays out of the heat? Are you saying that a 2 to 4 hour burn heats for 2 to 4 days? How many heating degree days do you have?

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No belt but the motor is outside the fan wheel housing. I’ve used fans with the motor in the stream before but they only last 1-2 years. There is no heat left up there, no warmer then my breath, but moist and ash dust will ruin them.
To heat my relativly large tank properly I will have to refill the hopper ones or sometimes twice, depending on wood quality. Total burntime 4-6 h. Heat lasts generally 2 days in winter time and up to a week in the summer when only fresh water heat is used. I also have solar panels but they are pretty much useless in this country. I need house heating for 9-10 mounths a year.


I have to ask! Did you build this boiler??? I have seen commercial ones like that but making a restriction that will stand up under the intense heat, I thought took some special materials.TomC

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I’m sorry If I led you to belive I built it myself. I’ve done all the plumbing and installing, but I have NOT built my boiler. I thougt I had made it clear I’m a crappy welder. I bought it from a local welder shop.

I did on the other hand make a simular working “stove” 20 years ago. I replaced the old boiler oil burner with my stove and attached it to the boiler. I ran it for eight years. I made it from an old hydraulic oil tank that i cut apart and dressed it inside with firebricks. Same downdraft concept except no water mantel which resulted in a sauna hot basement :smile:

My new, 12 year old, boilers restriction is made of the same material as in firebricks - ceramic cement. A small amount of small nails are added into the goo before hardening, for reinforcement.
The restriction/cumbustion tube can easily be changed out through the front door if needed. After an hour of burntime it’s glowing red hot, but still holds up good after 12 years.