Homemade Pellet Burner for existing boiler

Around the winter of 2011 I was feeling a bit cold because my house is not properly insulated and since electricity was (and it still is) expensive, the idea of building a pellet stove came to my mind. I did not even think about buying an already built stove because (you can guess it)… they were expensive. Around this time pellets were pretty cheap so they were a perfect solution for this problem. I contacted a  great friend in a metal workshop to know if he could supply me with the materials and he invited me to work in his workshop. Until this point I’m not  even sure if I had welded anything but that wouldn’t stop me:  the smoke did (but that is a problem for later).

Around a week after starting, this was the stove that I had:

 

The motor attaches to the bracket on the right side of the image (at an angle). From there, an auger doses the pellets. On the bottom of the image you can see two computer fans on their supports: one was to help the combustion and the other to spread more air around the house.

A motor is bolted onto the bracket that is seen on the first picture. This motor is connected to an auger that slowly drives the pellets into the burner pot. The pellet deposit is attached to the straight square pipe welded into the skewed round tube. Bellow this pipe, a 12V computer fan blows air to the burner pot. The smoke should leave the stove from the round opening above the skewed round tube. On top of the stove we have an air chamber where cold air is drawn to and heated. My problem with this first model was that the smoke was leaving the stove from the correct place but also from the pellet tube. I had built both openings too close and this model had to be scrapped.

After this first iteration, I started thinking about 3D modeling a new one. So I learnt the basics of Google Sketchup and the result is available below:

This iteration was much better than the first one: an ash tray was present, the design is more appealing, the pellet reservoir is built in and has a much higher capacity and the presence of glass allows the viewing of the flame. However, more or less around this time I stumbled upon a system meant to adapt to existing central heating boilers (that used diesel, just like the one we had) to use pellets. We were not using our boiler much and a system like this is more efficient, heats the whole house (if needed) and is centralized. However it had a cost of 1500€ that I was not willing to pay.

A few days later after getting to know that this system existed I had my first prototype. It can be built by anyone willing to do it and uses common available materials.

The combustion chamber is a round pipe that fits the existing boiler. If your boiler doesn’t have a reasonable opening, I suggest that you enlarge it. This pipe needs another one, usually at an angle and to the back where the pellets fall. The dosing mechanism for the pellets uses an electric drill that is powered on in short bursts. The bursts allow for a fall of just enough pellets to keep the combustion going. As for the ignition, I used a diesel glow plug connected to a relay and an ATX power supply. Controlling all of this is a mighty useful and versatile Arduino! The Arduino had the times and cycles programmed: one for ignition and another one for keeping the flame going. To check if the flame was still lit, the LDR from the diesel system was used. I also used the existing blower. Bellow you can find some photos of this project. It is not pretty but keep in mind that this was a prototype. I even used water bottles for piping because it was what I had laying around and the pellet deposit is… the body of the first pellet stove!

The whole thing
The box that is visible in the bottom left corner contains a power supply and an Arduino that controls the whole boiler
Visible is the auger, ran by the electric drill that doses the pellets.

This worked for the winter season of that year. At the end I knew that it worked and that I could build everything for a final version.

In the meantime I acknowledged myself with other systems already on the market and found a really good guide for building a proper burner on eBay. From my already existent experience and all of this I unified altogether in the final version that works every winter in my home. I bought a better motor, controller, flame sensor and igniter and with a lot of metal working and welding I reached the final version. Although it was not free (the whole project cost around 250€), it was much cheaper than a bought system and I learned a lot from several different fields.

The controller is fixed on the wall. The container of fuel is the blue drum. Above it, the motor that pulls them up (with an auger) and drops in the flexible tube that leads to the combustion chamber.

 

This final version can be built and tuned in less than a week if you have the materials and tools. I’m available to help if anyone has any questions. Thanks for your attention!

Leave a Reply

Your email address will not be published. Required fields are marked *