I'm sure many of you have found little tweaks to make your hand fed appliance more efficient. I thought it would be cool to have a thread packed with these discoveries.. These stipulations would pertain mainly to Anthracite. I have a hand fed furnace. This is what I've learned so far.....Combustion Air
More primary air entering the firebox = more heat being produced. Its important to have just the right balance of combustion air, since secondary air can just carry heat up the chimney. Primary air must be forced to travel up thru the coal bed and not have any other option, no way to bypass the coal bed, so that all its available oxygen can be used. I've found that best efficiency is achieved when there is sufficient air coming in under the grates and just a smidge of air over the fire to burn up gases off the top. Which leads to my next topic -Draft
Draft is a big one. Just the right amount of negative pressure in the firebox. On my Clayton it seems to be around a .03" WC. Too much draft will pull heat thru the firebox too fast. Too little draft, not enough combustion air gets in for combustion. Proper use of barometric dampers and manual dampers help regulate these. We want the heat to spend as much time in the fire box as possible so it can be transfered outside the firebox before exiting the chimney. Which brings me to the next topic - Heat Transfer
Heres one that took me a little while to stumble on to. Between the fire and the heat we feel is a steel wall. I've found that keeping the inside of the firebox clean by brushing ash off it once a week, greatly improves heat transfer from the fire to where I need it to be. This includes the build up of ash in the firebed itself. This is a big factor for us owners of the V shaped firebox.. More ash along the sides of the coal bed insulates heat transfer to the bricks, ultimately slowing heat transfer thru the steel and cuts down the surface area where heat is being transfered. Which means I should shut down and clean out a little more often than I do...Surface Area for Heat Transfer
More surface area for heat transfer = more heat is transfered. I assume thats why some appliances have tubes of moving air or water in the firebox. Tubes greatly increase surface area for heat transfer. Mine has no tubes, I've considered adding some.
I've found a simple way to increase surface area for heat transfer. I leave the ash pan out between shake downs. In the picture below, heat is radiated downward heating the bottom of the ash pan area. Directly underneath that, there is two inches of space where the blowers are sending in air to get heated and be sent thru the duct work.. I've noticed a substantail amount of more heat doing this, mainly in the first half of a 12 hour burn, when that heat is cascading down onto the floor of the ash pan area.
And what about flue pipe heat transfer to the room? A foot out from the furnace the pipe is 180 degrees. I have at least 10 feet of flue pipe in my basement before it gets to the chimney. Right where it enters the chimney, I can lay my hand on the pipe and its comfortably warm. So if this is all the heat thats left from my burning mass of coal thats finally going up the chimney, How efficient is my heat capture totally? 80%? More? I'd love to hear your opinion