Okay guys, I've been busy this past year reworking my central heating system. Last year I had Amos at D.S.Machine make me a custom 304 stainless steel wood boiler. It's basically the same as one of their current models, but slightly smaller.
I know, why didn't I get a coal boiler? Well, I wanted to first get a dedicated indoor wood boiler so I can burn wood year round in order to knock off my gas hot water heater by way of a 85,000 Btu side arm heat exchanger. My hot water heater is on the floor above the boiler. Besides, anthracite coal is now $250.00 a ton bulk here in Pittsburgh, plus it would be hard to keep going year round if it isn't a stoker. Then if I'm going to burn anthracite for just heating domestic hot water, I may as well just burn natural gas, it now cost the same.
So, over the past year I've been researching this forum and studying boiler plumbing options. I ended up deciding to use all 1 1/4" copper pipe with a pressurized system. I installed a 95,000 Btu at 10 gallon per minute water to air heat exchanger in the natural gas plenum and a 85,000 Btu copper water to water side arm heat exchanger for the domestic hot water.
I'm using the 50 gallon hot water heater as my gravity dump zone through the use of a unique custom made Injector Tee. Here is a link to what a Rayburn Injector Tee is. http://www.torrens.org.uk/HowTo/Injector/index.html
Since I have two supply and two return taps on the boiler, I'm using the rear supply tap for the pumps and the center supply tap for gravity flow. One pump goes to the radiation and the other pumps to the hot water heater side arm for faster recovery. When I lose power, the gravity flow from the center tap is free to flow into the domestic hot water side arm heat exchanger. In normal pumped operation, the pump actually induces the flow from both taps to the side arm heat exchanger. The Injector Tee allows the incorporation of gravity and pumped operation without the use of swing gates or zone valves. When I first saw this Injector Tee, I knew I had to use it in my system. It really works well.
Another thing that I was wrestling with, is the fact that the D.S.Machine Wood Boiler water jacket doesn't enclose the rear of the stove. So, I decided to install a 304 stainless steel 55 gallon drum, built from a couple of barrel stove kits, in order to recover as much heat as possible before it goes up the chimney. This addition has proved to be a wise decision. The reason is that the wood boiler forms creosote inside, then the smoke is ignited by the secondary after burner in the top of the boiler, it then goes into a 6" 90 degree elbow toward the barrel clean out door, allowing the ash to fall out of suspension into the barrel, then rise to the rear flue exit before going into the chimney. The smoke is then pretty clean. The stovepipe has kept clean and the chimney now only puffs out white steam, with a cleaner liner.
I did allow for the future addition of an anthracite coal boiler and more radiation. So I'm still eventually going to put one in, just not yet. I need more time for more studying the best anthracite coal boiler solution and a lot more money to make it a reality. So, I'm willing to wait until I get the anthracite boiler I want. Until then, I'll keep reading this great forum in order to make the best informed decision regarding the purchase selection of my anthracite coal boiler. There are a few really good ones being made and it makes it a tough choice.
So, now I'm busy playing and experimenting with this new system to see what it is capable of doing. My wife says that she likes the more even steady heat supply verses the hot air wood/coal furnace. It is also burning about 1/3 less wood than my Clayton does to produce the same comfort. I may have to add one of my Clayton wood/coal furnaces back before the winter season for added security, but we'll see.