DavidW1820 wrote:Has anybody here had any experience using an industrial duty centrifugal exhaust fan with radial blades to maintain an ideal draft in a boiler firing soft coal. My thought was to install it next to the chimney and use a standard draft control inline between the fan and the boiler to prevent excess draft. I figured there would be many benefits. Much smaller chimney required, much stronger draft in any weather condition, no puffbacks when loading. Only downside I see would be the periodic cleaning of the housing and fan blades and the cost of the fan and electricity to run it. They can be had with temperature ratings to 800 degrees which should be far higher than the flue temp of a typical 200,000 btu boiler, hand fired. It would seem to solve many of the problems people have with burning bituminous coal in smaller hand fired boilers. I have not seen any commercially available powerventers specifically designed for solid fuel use. They are all designed primarily for gas combustion.
The AHS and AA boilers have internal combustion inducing fans. Both use Anthracite coal exclusively. Neither has a feedback control system to vary the blower speed based on some measurement. While such a system would get more BTU's out of the fuel the cost would be very high. Ideally you would measure the flue exhaust gases and compare what you measure to the ideal coal combustion chemistry equation and adjust the air as needed. It's done for power plant sized boilers but for even large residential boilers it's just a pipe dream. Designing a reliable measuring system for the corrosive flue gas environment would be quite an engineering challenge.
DavidW1820 wrote:I understand your point. If in the unlikely event that happened, there would still be a fully functioning chimney to fall back on. I'm not advocating a dryer vent poking out of the side of the house. There would be a 30 foot class A lined chimney to exhaust the burning coal. I would imagine that with a sudden power loss and a full load, the fire would gradually die down and go out. You could easily use battery back up or a generator too to keep it going. That's what large industrial and utility boilers do.
But such large industrial and utility boiler installations aren't living spaces. And they aren't designed for sleeping, i.e. long periods were a failure goes unnoticed.