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Not much to add. I did order seals for the furnace. I will also share another configuration I have considered. A vertically oriented combustion chamber induces significant draft. So, in principle, it is possible to do away with the blower fan. However, the steam generator would present more obstructions to gas flow and change the output, so it is really too soon to know if this will be viable with my design. I tend to think it's a reasonable prospect based on the performance of rocket mass heaters that often burn very fast for short periods and using similar fundamental design (high temperature insulated and vertically oriented combustion chamber), and often providing extensive duct work that presents obstructions to gas flow. However, a mechanical means would be required to control the furnace output. I will be using a hydraulic mechanical control system (using feed water pressure) to actuate control switches, and I may be able to use this system also to position a damper to control the furnace. That is a year or two down the road. All I need determine soon is whether or not the furnace can generate heat at the required rate - and then some, hopefully - and without the blower fan. Of course, I want to see how fast it can burn wood with the fan as well. So, I am looking at a lot of testing in the near future.

There are advantages to eliminating the blower fan that include (1) not being dependent on the reliability of a blower fan, (2) likely a more robust mechanical control system, (3) no need to seal the top of the furnace and hopper extensions as the furnace would not be under a positive pressure. However, there are disadvantages: (1) I suspect it would be much easier to start the system from cold using a blower fan, (2) the output of the system would likely be more consistent with a blower fan - especially one with fairly high static pressure which I have sourced, and (3) while I am not sure, I suspect it would be easier to configure a system that stops a blower fan with simple switches rather than a hydraulic mechanical actuated damper.

Updated 10-08-2019 at 07:19 PM by buenijo