The first week of using my boiler has been very successful. The boiler is very useable right off the bat. Here’s a video that shows some highlights and discusses some future modifications I plan to incorporate:
Since making the video, I have determined that using dry wood makes the extra heat riser pretty much unnecessary. It only required a very simple modification to the grate. Let’s take a look at the grate to understand how my modification works:
Keep in mind that there are two 1″ I.D. secondary air tubes that run in the center on the underside of the grate that extend into the entrance of the secondary combustion chamber. You’ll note that plate with holes welded to the top side but not the bottom side. I noticed that the entrance to the secondary combustion chamber was free of soot at that level, but badly covered with soot on the bottom half:
After making this observation, I added a small piece of the same metal to fit under the secondary air tubes. What was happening was the blower was injecting too much air under the fire, escaping underneath the grate, cooling the secondary combustion chamber, and starving the primary combustion.
This baffle slowed the airflow, increasing the temperature under the grate, and the backpressure gave more air to the primary burn. This resulted in an extremely clean burn as you can tell from this photo:
This has resulted in a very clean burn within the first 5 to 10 minutes of start up, which continues on as long as the boiler is running with a good bed of coals. Another great thing about this design has been the complete lack of sparks and ash escaping the stovepipe. I think the exhaust is some of the cleanest that I have produced.
In my next post, we’ll discuss my decision to insulate the outer body of the stove and lower pipe to further increase efficiency as well as delve into some of the calculations that brought me there. In my next video, I plan to show me building a fire and demonstrating how quickly it burns clean.