Converting a Fire Chief FC700 for Coal

Hi guys, I poked around on this site last winter to get some info on burning anthracite coal. I have a Fire Chief FC700 that's designed for wood and soft coal. http://www.amazon.com/HY-C-Chief-Furnace-Roller-G ... B009A4WSNE I found a thread on here last winter on blocking the secondary air channels to pull air through the fire, which worked great. I also removed the forced air fan that blows across the top of the fire and blocked the hole, so right now, the heat is controlled strictly by one screw damper in the ash door. I burned coal for about 6 weeks at the end of last winter, but it seemed to take a lot of babysitting, and I had a hard time getting steady heat; it seemed either to hot or too cold. If I had the screw damper open all the way, it wasn't enough air, but if I cracked the ash door it would overheat. I'm planning to install a mano and baro damper in the stack, but it almost seems like I don't have enough draft, and wouldn't a baro make that worse? I have a 30 foot SS lined and insulated chimney, so draft shouldn't be the problem. I'm considering mounting the forced air fan in the ash door in place of the screw damper, but I'm afraid at idle, it won't pull enough through the fan, given that fact that it seems to already not pull enough through the screw damper. Therefore I would have to keep the fan damper open quite far to get enough air at idle, but then it would be way too much when the fan kicks on with the thermostat. Any ideas? Limit switch in the air plenum to keep from overheating? Electric auto damper like the Harman in this pic? Harman furnace.jpg

I would start with getting a manometer to determine just what the draft is.

I would suspect that air is still bypassing the grate or that the bed depth is too shallow, or so spread out that sections are allowing the bulk of air through without burning.

It seems to burn very evenly, and when it's loaded it's a good 8" deep. The firebox is 28" long and has a single roller grate at the bottom which makes it about 5" wide at the bottom, then there's a row of fire bricks on end at a 45° angle until it reaches approximately 16-18" wide, so it holds about 120 lbs of coal when it's fully loaded. I will install a mano and baro, and go from there. I would like to set it up somehow so that it's controlled by the thermostat upstairs though.

First read through Lightning's posts with his Clayton which is very similar. You will have to devise effective means of clearing ash , as he has done.

The manometer will tell you very quickly if draft is adequate. From there you can determine if that manual air opening is enough, so far it is not, but any other cause has to be eliminated.

Rather than using a fan for combustion air it would be much better to use a motorized device controlled by thermostat, to open and close the air intake , which could be larger if need be. there are several threads about doing this with stoves similar to yours. Use the search box in the upper right. Hotblast and Clayton are key words.

I agree that it would be better to have an electrically controlled damper door rather than a fan. I just priced the auto draft control assembly that's on the Harman, and it's $380. OUCH.

The yo-yoing of heat output is caused from a variable draft. You need a barometric damper installed. It will fix the problem. I had precisely the same problem before I installed the baro.

Thanks, Lightning. So once I have a baro on there, what happens when I need more heat upstairs? Like when a thermostat would be calling for more heat? Without some sort of damper on the intake air, how does it regulate the heat when it's warmer or colder outside and needs more or less heat to keep the house warm?

lewis81 wrote:I agree that it would be better to have an electrically controlled damper door rather than a fan. I just priced the auto draft control assembly that's on the Harman, and it's $380. OUCH.

I had in mind something like a hot air motorized damper control. Check ebay. There is a thread on this forum of someone doing that, but I can't find it. Maybe Lightning remembers it.

lewis81 wrote:Thanks, Lightning. So once I have a baro on there, what happens when I need more heat upstairs? Like when a thermostat would be calling for more heat? Without some sort of damper on the intake air, how does it regulate the heat when it's warmer or colder outside and needs more or less heat to keep the house warm?

Keep track of how many spins open you have on the primary combustion air. Mark the top finger grip when it's closed to make it easier to count rotations. With a steady draft pressure (which is what the baro is designed to provide) you will find that each rotation of the spinner will give you a predictable heat output level. You will still need to adjust it to suit your heat demand needs (just like any stove that isn't controlled by a thermostat), but the yo-yoing of too hot to too cold and endless trips to the basement to adjust your primary air will be over.

Keep track of the rotations on the spinner with the conditions outside. In short time you'll only need to adjust your primary once or twice a day to keep the house temperature steady.

Once you set the baro with a manometer you won't want to change it. Any change made to the baro will also change your heat output levels per rotations on the combustion air spinner. I would suggest setting the baro at -.04" WC to start with.

I just reread your first post. You mentioned that the spinner wide open didn't quite provide enough combustion air but then cracking the ash pan door would make it over heat.

I have a couple solutions for that. First, try some stove size coal. Stove size heats easier with less combustion air. It's very puzzling indeed but I believe it has something to do with the bigger spaces between the coal pieces.

Secondly, you can add custom primary air control like the one on mine. I don't even use the spinner anymore. I simply measure how far from the floor the pointer is set to give me my controlled primary combustion air setting. This should get your gears turning a little.

I don't recommend getting in the habit of leaving the ash pan door open (unless you're igniting a fresh load of coal). Under the right conditions it could be very dangerous.