Things seem to be real quiet on this forum lately so I thought I would post a collection of my random thoughts and experiences converting my central heat from oil to coal. It's been 2 1/2 years now and I think I am just at the point where I think all of the loose ends are tied up.
The house was originally heated with coal (cast iron radiators) so switching back was pretty simple. There was a handy spot for a coal bin right next to the boiler location so it was a simple matter of rebuilding a couple of 8-foot walls walls to contain it. I used 2x4 construction on 12" centers with joist hangers and lots of anchors in the top and bottom plates to make sure it could handle the pressure. Even so, loaded with 6 feet of coal the wall bulges by 3/8" or so. Glad I didn't go for lighter framing!
I choose a Watts 70A to temper the water off the domestic coil. It requires heat traps, a throttling valve and in my case a check valve to make it work right. And it works pretty well except in very low-flow situations when the output temperature soars close to the boiler temperature. The only time I notice it is when I am using the trickle valve in the shower
. If I was doing it again I would try one of those double-throttling designs instead.
The first problem I had when I first fired it up (in January!) was not enough heat. Answer: Open the primary air damper all the way.
The second problem showed up when the weather warmed up: an irritating amount of unburned coal in the ash. Answer: Double the timer setting and cut the coal feed in half during warmer weather. The secondary combustion blower the Keystoker has will keep the fire from going out but isn't enough to keep the fire vigorous if the house isn't calling for heat for a long period of time.
I made a couple of modifications to my KA-6: insulated the top, flipped the small blower over so the oil hole is on top
, reglued the ash door gasket with RTV rather than stove cement, and drilled oil holes in the stoker bushings. Also had a second flow control valve plumbed into the return line just before the connection to the bypass loop to keep the hot water from convecting out and being wasted.
Cleanout and Storage:
After the usual scraping and vacuuming, I seal up all the doors and openings and put a 60 watt heat emitter in the bottom. They last a lot longer than light bulbs (5-10 years) and are sold to heat birds and reptiles by most pet supply places. So far it has worked very well. To clean out the stove pipe, I brush it out real good, spray a baking soda, water, and dish soap solution on it and flush it out real good with the garden hose. Using soap and rinsing well makes a big difference. Corrosion has been nil since I started doing this.