Hand Fired Coal Boiler Problems

IF anyone can help with my problem it would be great. First I will explain my setup. I have a hand fired coal boiler (Chappee). It is vented with 6" double wall pipe (approx. 12' with one 90) to a brick (clay lined) chimney 20' (half inside the house, half outside).There is a baro installed 12" from the boiler exhaust. The supply line runs into a copper sidearm off of my electric hot water heater and then into a radiator which I installed into the plenum of my warm air furnace. The circulator pump runs continuously. There is a calorstat (non electronic temp sensor) which opens the damper door to allow air into the ash pan door to feed the fire. It begins to open on temp fall at 180 degrees.I have my warm air oil furnace set to turn on if the aquastat senses the boiler water temp at or below 160 degrees as a backup.
My problem is this: I noticed last year that when it got cold (30F or below), the oil was kicking on more often than not. Everything was working correctly, damper door beginning to open at temp drop below water temp of 180F in boiler, but the fire was slow to get really cooking to maintain the water temp. For example, at a call for heat my fan only would kick on in the warm air furnace, water temp in boiler would be at 180. If it was a long enough call for heat, say 5 minutes, the oil burner in the warm air furnace would kick on and finish the heat call (oil set to come on when water temp falls to 160F in boiler) I found that setting this temp any lower would result in the fan running for a really long time. So I figured I would install a draft fan in the exhaust pipe to induce a draft. I installed a field controls DI 1 draft fan and tied it through an aquastat to the boiler. I have toyed with all different temp settings on the aquastat. Whenver it comes on I instantly get a draft of .06. The baro is set at .02, the max setting so the baro opens fully whenever this fan comes on and I still have a .06. It does get the fire cooking quickly, but I think I am wasting a ton of coal doing this. I have tried setting it to come on at temp fall of anywhere from 180 F to 160F. It almost seems that the draft inducer will run for a long period, getting the fire cooking hot, but can't overcome the 5 degree aquastat differential because it is sending so much heat up the chimney,

My question is this at what point (draft reading), am I wasting coal as opposed to getting my fire to keep up the water temp? It seems that at .06WC I am wasting coal. But I am now going around in circles, adjusting this and that. Also, if I don't use the draft fan, is there anything I can do to get the boiler to maintain water temp faster. I believe the boiler is sized right, it is rated at 122,000 btu, and I am heating 2000 square foot house. Again, it will only take less than 5 minutes of the warm air furnace fan blowing through the radiator to drop the entire systems water temp to 160. I am pulling my hair out. I have a gate valve on the supply line that I have tried closing halfway to slow the water flow down, thinking maybe the water going through the boiler would have more time to heat. I have also tried adjusting the gate valve on that runs on the bypass between the supply and the return (full open lets more hotter supply water to enter the return water), but have had no luck. Any advice is appreciated. Thank you in advance.

How about using an open-on-rise temperature sensing switch. Put this on the flue pipe. let the Aquastat turn on the draft fan, but run the circuit throught the temp switch on the flue pipe,, then when the fire is cooking real well, the temp switch will shut off the draft inducer, allowing the draft to drop to the .02 setting you have with your baro.

Hopefully this would save some coal.

Greg L

Just a WAG but it sounds like you're pulling heat off too fast with your fan speed. I found an old 2 ton air handler and made up a plenum for my 80K WA heat exchanger. I was really concerned that it would not have enough air movement to satisfy the house's heat load. The air speed/flow is probably 1/3 of what our propane furnace produces.

With 150°F water coming in we don't even really feel the warm air coming out of the ducts but it maintains the heat at 74°F day and night. Not only that but it's so quiet you don't hear it either, just a nice even warm house and floor. All this in a home with no basement and cathedral ceilings with 6" of insulation is astounding to us.

Will it work when the temps drop to -10°F? I don't know but we will soon find out.

As an aside I sold my Chappee to my father in law and he loves it so far although he is using baseboard. He couldn't believe the heat transfer and how fast it got to temp compared to an older RiteWay coal stove he had been using.

Here's another thought, would you still have warm air flowing if you dropped your water temps to 140? 150?

If that would still maintain your warm air couldn't you drop your cut in temp on the oil furnace? Then the furnace wouldn't kick on until the lower temp, letting the coal do all of the job.

I'm just a mechanic thinking along those lines and my own experience in my house.

Here's my 2 cents worth of advice. First, I am heating twice the amount of space as you with a boiler rated at 95,000 BTU so your boiler is big enough. I would disable the oil burner by tripping the reset or removing a wire from the burner transformer. Don't panic when the water temp drops to 160*. I run my boiler at 140* most of the time. During the recent cold snap, I bumped it up to 150*. The first year I had the coal boiler, I operated it like it was the oil boiler. That is I set it for 180*. All that did was burn a $hit load of coal and wasted alot of it. I'm not at all familiar with a Chappe but let it try and do the job without the oil burner kicking on.

Like coalkirk, I fire my boiler at 140 deg. and I too, bumped the temp up to 150, exactly as he did. We just had 10 deg temps overnight (10 one night and 12 another). In years past, during zero deg weather I fired at 160, and burned considerably more coal than I wanted (and more shakedown and firing than I wanted to do), so if it's really cold, I let the oil boiler back it up. I too have a sidearm water heater, on the return line that pre-heats my domestic h2o prior to the coil in the boiler. From Thanksgiving '08 till April '09 I burned 3 tons of coal and 105 gallons of oil, heating 2400 sq.ft. house and I have a 40k hot water unit heater in the garage,
that I do use often.

I'd cut your boiler temp down and as was said previously, slow the fan down in your furnace and let it run longer. You'll get more even temps in the house. Have fun deciding what to do.

What kind of heat exchanger are you using? You say a radiator. If you don't have an A/C evaporator in the furnace you may be able to install a hot water heat exchanger in the ducting wear the evap. would normally be. One that is designed for this purpose.
I remember looking at the Chappee boiler about 20 years ago, but don't remember much about water volume. Do you know how much water it holds. My boiler holds 35 gallons, which
is enough reserve so that when circulator kicks on there isn't much temp fall. My system also gravity circulates (baseboard loops).
Another idea is a hot water storage tank if your boiler has minimal water capacity.
Just some thoughts.

I'd be glad to check it out if you like. I agree with the boiler temps from other members. PM me if that would work out for you....
The balance point and break even line are not a fixed value as you have found out........you can spend a half a million on controls to save $100.00 in coal........

Coalkirk beat me to it..... I'd add a switch to shut off the oil burner. We all accept that burning a solid fuel requires a certain amount of work....flipping that switch as needed would be part of the work load. I'll bet you find that you only flip it when it hit's 20 below zero.

I always thought that was the design purpose of "The Clapper" switch. Clap on, Clap off!....
Now for all of you who clap to call the animals...

I guess I forget about turning the oil boiler off..it's just like a 10 billion Dubai bailout!
I get heart palpitations when the boiler aquastat clicks.....but the switch is off anyway.......
Damned coal boilers.....It makes you forget the"Lock Out/Tag Out" procedure we all live by!

If you have a wife, significant other....or some other form of life friend/companion, (even farm animals)...
PLEASE DO NOT EXPLAIN Lock out/tag out. Tooooo much info for them. 'Lock out' is all they need to know!

First I would like to thank everyone for their responses. I do apologize for the delay in responding. (Fedex Contractor so we are slammed right now-14 hour days and such). I did think about slowing the fan on the warm air furnance down, but at my 1.0 gallon per hour rate I am already on the slowest setting allowed which is medium. I take it this is to make sure that I don't overheat the exchanger when boiler is firing. What happens with my fan is it will run forever once the water temps get down under 165. Is this just something I should deal with while using the coal?---I don't want to slow down the fan speed in the event the oil does have to come on. II am going to try to lower the water temp and have a go at that. Thanks again for all the advice. The "radiator" I spoke of when I was half asleep, mind bending from my issue is a water to air heat exchanger.

In response to LSFarm, does anyone know if there is a draft switch? I know they have draft proving switches to prove whether or not there is a draft, but is there one that you could say-break on draft rise and set to .04wc?

CoalInNH wrote:What happens with my fan is it will run forever once the water temps get down under 165. Is this just something I should deal with while using the coal

Let the fan run. I run my circulator fan constantly and my house stays a nice even temp. I'm only sending water through the exchanger at about 90* most of the time.