off the grid coal boiler

Re: off the grid coal boiler

PostBy: Yanche On: Thu Mar 05, 2009 12:39 am

I agree with Bob, I grew up with a hand fired gravity feed boiler system. Radiators got hot and stayed hot. When my Mother couldn't handle the coal and ashes and longer I replace the boiler with natural gas. A fraction of the water volume in the boiler with a single circulator pump. Both worked well. I wish I would have saved the Burnham coal boiler. It was smashed and sold as scrap.

Today I wouldn't know how to design a gravity circulation system. I know of no textbooks on hydronic design for gravity flow. Anyone know how to design gravity flow systems? Pipe sizing, flow rates, temperature differentials, etc.
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea

Re: off the grid coal boiler

PostBy: Berlin On: Thu Mar 05, 2009 4:07 am

"My house had gravity-fed radiators for years. Boiler got hot, radiators got hot, very simple and it worked flawlessly. The radiators heated more evenly and almost as fast as with the modern circulator-pump system that replaced it. The new one may be more efficient, but that's due to boiler/oil-burner efficiency, not the circulation system. I think a gravity system requires greater water volume within the boiler than with forced circulation, but I could be wrong on that."

yes, gravity hot water is an option too.

but, single pipe steam is easier to design, one can shut of radiators not in use (to a point) without worry of pipes freezing, there is NO need for electricity ever and once the boiler is called for heat steam arrives very, very fast to the radiators, there's also only one pipe to each radiator, less time and $$ plumbing. as you may be able to tell i really, really like steam heat :)
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal

Re: off the grid coal boiler

PostBy: rberq On: Thu Mar 05, 2009 7:29 pm

rberq wrote:Anyone know how to design gravity flow systems? Pipe sizing, flow rates, temperature differentials, etc.

I wish I had taken photos before my system was dismantled. (Actually, I wish I had not replaced the system at all, since I have used first wood and now coal since then, so the new super-duper $8,000 system hardly ever runs except to make domestic hot water.) As to design, there were two large pipes, about 4 inches, coming out the top of the boiler, and two more large pipes returning to the boiler about three feet down from the top. Other than that, almost everything to and from the six radiators was 1 1/2 inch pipe, and it all ran just below the floor joists. Return lines were no lower than feed lines. Even the 4-inch return lines didn't drop down from the joists until they were almost above the boiler. There may have been five feet or so of intermediate step-down sized pipe between the 4-inch and the 1.5 inch; I don't remember. Horizontal distance from boiler to radiators ranged from about four feet to about thirty feet. As far as I could see, all the motive force for circulation came from the boiler itself and the six or eight feet of big pipe in and out of the boiler. There didn't appear to be anything at all complex or specialized about the design.
Hand Fed Coal Stove: DS Machine 1300 with hopper
Coal Size/Type: Blaschak Anthracite Nut
Other Heating: Oil hot water radiators, propane