Yanche, thank you for your kind words. I would hope that some of the manufacturers out there would rethink their current designs and put some more sophisticated controls into their coal burning products. Harman does this with their line of pellet fired equipment, yet the coal fired stoves and boiler, get the 1980's electronic timer control.
Chris, the PLC I used is one that my company distributes so the choice was fairly easy. There are a multitude of controls on the market that could do the job, their ability to process analog signals is the key. As to my house, the boiler is located in the basement and provides a welcome amount of additional heat there in the winter. In the summer, it gets pretty warm so I open a screen door to let some of the excess heat out. We normally don't run AC in the summer, just an attic fan, but it does add to the heat. I've added insulation under the sheet metal to help with the heat loss, it adds maybe 5 to 10 deg to the average boiler water temperature. All in all a small price to pay for the greatly reduced propane bill.
Kirk, The flex hose with the outside air is a relatively recent addition, I didn't have it during the summer months. I ran with the restrictor plate, maybe half open with the combustion blower running all the time. My chimney draft was about .02" with outdoor temps in the 80's, but I never had coal gas. I did experiment with it open all the way and still had no coal gas smell. The chimney is a double wall insulated SS type. It draws very well in the winter, almost too well, the baro damper swings open quite a bit, but its doing its job. The latest mod was the variable speed control for the combustion blower. When the stoker runs, the blower runs full tilt, when its off, the blower slows down to less than half speed. This should keep a larger bed of coals and reduce the excess air flushing heat out of the boiler while still maintaining the fire during long periods of idle.
This boiler and burning coal has turned into a hobby for me, I look for ways to tweak the operation and controls to maximize the performance and minimize the fuel useage. Some people might think I'm a bit crazy, but I'll bet people here know what I'm talking about.
Last edited by Highlander
on Sun Feb 03, 2008 5:51 pm, edited 1 time in total.