Anyone have a boiler or furnace NOT using forced air?

My boiler (Hydrafire) only has a thermostatically controlled flapper for air entry under the grates. It has two 1/4" holes in the door for secondary air over the fire which I can block with simple magnets if need be. I have not burned coal in it yet. It's 28 yrs old or so. I posted info and pics previously. It is a boiler with a water jacket. I was designed and tested for anthracite and wood and I have only burned wood. I have a new baro damper installed. I was thinking of drilling some number of holes into the front of the boiler in the ashpan door below the grates. With these quarter size magnets with a hook that sticks out (they are made as hooks for hanging stuff) I figure I can adjust a minimum air flow rate and allow the thermostat to open and close to maintain the correct temp. range. The flapper is either full open or full closed. IThe flapper is somewhat adjustable by fiddling with the chain connections so that I can make it so full open is wide open or a little less if I need it to be. Or I can set the chain so the flapper never controls completely. I just got a Hitzer 50-93 for the living room. I have studied how it receives air flow (also w/o use of a blower). It has a sliding air setting in the front ashpan door and a thermostatic flapper in the rear to maintain temperature with no secondary air anywhere. That's why i figured with the addition of air inlets in the front of the boiler in the ashpan door I would be making it more like the Hitzer firing technique. The main difference is that my boiler thermostat moves the flapper either full open or full shut-nothing in between. Anyone have any thoughts on this? It seems like most people have forced induction even in there hand fed units. Anyone NOT using forced induction in a boiler or furnace???This was my original post and pics of the boiler.
Pics of my boiler cleaned up and my 3 tons of coal

I can't answer the question, but thought I'd remind you that heat can remove the magnetism from magnets. Might not, depending on temp, but if you're going to over heat to a dangerous point if the magnet falls off you might find a different way.

Good point-I had forgotten about that. I don't think it is a very efficient method to demagnitize something however.These magnets are actually very strong (they are designed to hold weight) and I don't think the temp. at the lower level would be that severe plus the fact that some air flow by the magnet would make that spot just slightly cooler than without the holes. I appreciate that warning though. I may have to do some experiments first.

I don't believe the temperature of the door to the ashpan area will be very hot.

I think your idea of of allowing a steady air supply, controlled by the placement of magnets over holes is a good one.. then let the moving flapper control the rest. But I would try your system with very few holes first.. depending on the size of your fire bed, and heat required for your house, you may not need or want too much uncontroled air..

Have you ever burnt coal in this unit with just the flapper controling heat output??

Greg L.

I don't know at what specific temperature magnets de-magnetize, and I'm certain that their composition has some impact on that, but for what it's worth, the cheap magnet on my Rutland thermometer didn't demagnetize and fall off the cast iron insert until she was sitting at 900 degrees for a while...

-- Mike

You might find something of use in my thread .. How do you feel about a thermostat controlled hand fired?. I installed a thermostatically controlled damper, which is wide open or nearly closed, nothing in the middle. It works fine. I think, with the other system you need a modulated system, which means you have to have power to make it move, either one way or the other.

LsFarm wrote:I don't believe the temperature of the door to the ashpan area will be very hot.

I think your idea of of allowing a steady air supply, controlled by the placement of magnets over holes is a good one.. then let the moving flapper control the rest. But I would try your system with very few holes first.. depending on the size of your fire bed, and heat required for your house, you may not need or want too much uncontroled air..

Have you ever burnt coal in this unit with just the flapper controling heat output??

Greg L.

I tried coal 1 time about 30 yrs ago but didn't know what I was doing. I just burned wood after that. If there is nothing calling for heat the boiler will hit the upper limit and the flapper door closes all the way. The wood could smolder there for quite a while but when the flapper reopened the wood could bounce back pretty quick. It worked great with wood once I got all the temp settings on the aquastats syncrhonized with the oil burner temp settings and circulator settings. I just don't know if the coal would have a harder time to get going if basically all the air were shut off (other than whatever leakage might be drawn in? I could simply adjust the flapper to not close entirely in its off position. I can also adjust the max open position as well to some extent. I just thought if I added some holes to the ash door and adjusted them with magnets it would be designed more like the way the hitzer stove works. The main difference is that on the Hitzer the rear flapper is thermostatically controlled w/o electricity and it is progressive in the way it opens-not just open or shut. The Honeywell aquastat on the boiler is just on or off. There are 3 of them. One controls the flapper and a small circulator pump to circulate water over to the oil burner to keep it warm One controls the low temp that opens the flapper and circulates the water. The other shuts the flapper at the high temp and the circulator keeps running until the temp drops below the low limit. Another opens a dump zone if the temp rises too high. It dumps heat into the baseboard of the largest zone in the house. I think it dumps it at around 210 degrees. Worked great with wood. Just never experimented long enough with coal. I'm still thinking a few small holes in the lower door might work best and let the flapper close all the way.

Dallas wrote:You might find something of use in my thread .. How do you feel about a thermostat controlled hand fired?. I installed a thermostatically controlled damper, which is wide open or nearly closed, nothing in the middle. It works fine. I think, with the other system you need a modulated system, which means you have to have power to make it move, either one way or the other.

I'm going to check that out right now.

M847A1072 damper control is what controls the opening and closing of the flapper on my boiler. Of course it recieves an open or closed signal from the aquastat that monitors the water temp. I kind of got lost in your experiment. Does your stove have any additional air inlet besides the one you hooked up to your controller?

Does your stove have any additional air inlet besides the one you hooked up to your controller?

No, there are no other holes. I've adjusted the draft slider to be "open" a little bit (each hole about 1/8"), when deenergized.

Are you happy with the results? Efficiency, control of heat output, etc? About how much surface area (sq. in. are you controlling) with how many 1/8" holes. Just trying to get a feel for how much air I might need to feed for maintaining a minimum fire during idling.

My system seems to work fine. Please see the video on the thread mentioned before.
I'm guessing, your boiler will work fine, as is.

I think in the spring and fall you may need a few holes to keep the fire burning.In the winter with a good draft 1 hole may be good.But you can always put a magnet over the other holes in winter.Good idea.
DON

I had a draft control as you describe on a Sears furnace made around 1920, it worked like a charm. Up until about 10 years ago Burnham made a coal/wood boiler (Woodlander) that used a natural draft too.

OK, I did it. I drilled 5 3/8" diameter holes into the front ash door. I built a small hardwood fire on top of the coals that went out at the end of yesterday's first trial burn. It had left about 1 " across the grates but the ones at the back had burned more than the ones in the front. Then after the old coals caught , I added another layer slowly so that I ended up with no more than 3 " depth. The rear firebrick lays horizontally in 3 layers-each brick is 4 " wide. The coals were lucky to be 1/2 way up that brick so 3" might even be on the high side. Anyway, this time I let the rear damper close all the way (which was pretty much ALL DAY and NIGHT.) I lit it at about 11:30 in the am and it is now exactly 12 hours later and it is still burning and the water temp is at about 210. We washed clothes, dishes, I took the longest and hottest bath of my life (to help my sore back) and I don't think the flapper even had to open. I started early today with all 5 holes left open and as the day went on I checked the condition of the fire. If it looked good I covered more holes with the magnets. Right now i have 3 of the 5 holes uncovered and it is still going good. The whole load is burning evenly this time. Last time the front died out first. I think the idling holes did the trick. I can't believe how long that small amount of coal can burn!!! Nearest I can tell I loaded a total of 1/3 cu ft. So I am guessing it has been idling at 1lb/hr or even less. I'm sure it will still be going for another 3-6 hours from the way it looks. That's as good as I could have hoped for in this 30 yr old boiler. I was afraid the long surface area would not be too efficient. I don't know why on earth I waited all these years to smarten up and switch to anthracite.

Welcome to the House of Anthracite.
You have now seen the light and will be rewarded with bounteous heat and hot water.
You will smile when it is cold out knowing the house is warm and your pocket has not been drained.
You keep your dollars in the US, help lower the unemployment rate, help balance the trade deficit, and keep your house warmer.
All this while paying less and not using some government run agency that will increase you tax bill at the end of the year.
AMEN!