Need Tips for Burning Slow in the Warm Weather

Stove:
1940s-50s Locke Stove Company 400C “Warm Mornings”, hand fired.
Big firebox, 16 inches front to back, 18 inches wide, 20 inches top to bottom.
In basement, tied into hot air plenum on existing forced hot air gas furnace.

Chimney:
Block with clay inserts. Half inside, half outside. Height is good, goes just past the second floor roof. No chimney cap. Manual damper, but a manometer to watch the true draft.

Coal :
Chestnut anthracite that burns into a red ash. (last 1 ton I burnt was chestnut, white ash)


We just had one of the warmest Decembers ever, Dec 2006. Looking at 7 day forecast we should see highs in 40s and even 50s for most all of the week, with lows in the upper 30s and 40s. I want to burn slow, but without burning out my fire … and need help.

I'm trying to learn my coal burner, it’s my first season. I can get plenty of heat off it and get an easy 8-10 hour burn from it, as long as I load it up. My routine lately has been 1 coal pail in the morning (about 20 lbs), half (10 lbs) when I come home from work, and 1 coal pail before bed. That keeps my firebox at a decent level which is important because when I run the firebox just enough, it will go out on me. Every few days I’ll load it up more trying to build the base back up.

I've been keeping track of how much I've burned and don't like that I burnt around 1500 lb last month, probably a more. That’s about 50 pounds a day.

This isn’t a horrible amount of coal, but my house gets too hot. 74 most of the day today. I don’t want to waste my fuel. I have my damper closed, still pulling -0.03 draft though its holes. I achieved the low draft by opening the secondary air open in the feed door, regularly it runs -0.05. Ash door air is closed, and heat spring is on “low”. This is the first time I had the secondary air open, and I noticed I ashed over the coal on top of the fire, so I don’t think I’ll try that again.

I’ve heard you can run pea coal to slow the air down. I’ve also seen people like Greg LS putting extra fire brick in their firebox to make it smaller. I’ve even heard you can put ashes on top of the fire.

Does anyone have any good tricks for this spring-like weather?

Hi Coal kid. If you have your under fire air turned all the way down, then the only way I can think of to reduce the heat output is to reduce the firebox size.

As you mentioned I have suggested to a few other forum members to do this. It has worked well for me, but I haven't heard back from other forum members if they had success.

The design of the grates and firebox floor will determine whether using a stack of firebrick will work. If you are able to stack the brick on non-moving parts of the bottom of the firebox and still allow the grates to move for shaking the ash, then you will be successful.

I had to put in a steel plate that rested on opposite sides of the grate. This left the grate free to move fore and aft when shaking the ash. You must block the grate such that no combustion air can get around the coal bed or the fire will go out.

A simpler method which you suggested may be to go buy a few bags of pea coal and try them to see if it reduces the heat output from the nut coal enough. With this method you know the fire will keep burning. If this isn't enough heat reduction, then reducing the firebox size is the only other method I can think of.

Maybe other forum members can suggest something else??

Greg L

Like Greg said the pea coal will dampen it somewhat but don't overdo it, and reducing the firebox properly is about it. Using ash will work but carries the risk of losing the fire. One thing I've learned, it's easier to open a window than try to figure out how to run Anthracite real low. The only real way is to switch to a stoker, they can run real low with a lower draft. It just doesn't work well with hand-fired stoves.
In Europe a lot of solid fuel heated homes (typically boilers) use a heat storage system. It consists of a large tank of water to capture and store heat, that way the unit can run at it's optimum even in warm weather and you don't lose heating when you take the unit out of service to clean etc. It also alows you to better recovery when it turns bitter cold.

Thanks for the tips guys. Putting ash on top does sound like you'd risk putting the fire out. That’s the last thing I want to do.

On further inspection I don’t think the secondary air ashed over much coal, maybe just a few just on top. I still had some blue flame from underneath on my first run with the secondary air open. I skipped my night and morning shakedown and left the secondary air open most of today, and my house was 69 when I came home. Too cold! (I had the thermostat on my gas furnace at 64 last winter, somehow). I overlooked the wind that we had today, and focused on the high temperature that was forecast.

I think I’ll pick up a bag of pea coal to see how it acts. Where I can pick it up I’ll see if they carry standard size fire brick. I don’t want to pay to ship it in. I think with some steel for a 1/2 inch shelf and some firebrick it could be done with my setup. I’d have to have it shutdown almost all day for it to cool down where I could work on it. I don’t know if I want to do that until the spring.

Your best plan as Greg suggests would be to reduce the fire box if possible using steel or ss steel plate and fire brick.. Make sure the area reduced does not allow any air to pass. See my attached for a home made reducer I designed using ss plate scrapped out of a dumpster before it was shipped off to the foundry.

If you do use standard carbon structural steel, expect it to rot out, at least any of the steel which see the hot fire.

The 2nd image cuts my box in half. The 1st image removes about 30% of the box. I've been using my 50% reducer all season. When is it going to get cold?

I've been reading all these posts about reducing the size of fireboxes because of the mild winter. I admit I don't know a thing about hand fired boilers but it seems the design of the Alternate Heating Systems multi-fuel boiler might be a solution. AHS uses a rotary grate system that allows shaking of individual grates. See their web site: http://www.alternateheatingsystems.com/ ... oilers.htm for a so-so description. Seems to me only shaking one of many grates would reduce the capacity of any boiler. Forum member "ktm rider" has one of these AHS multi-fuel boilers and burns bituminous coal. Perhaps he would comment on his experience in this mild winter.

Yanche

I don't have any tips for current hand fired boiler owners to deal with the mild weather. But anyone reading this thread and considering a coal fired boiler in the future would be wise to consider a stoker instead. My Harman VF3000 will idle along at a minimum btu output all week without a problem. It's btu output is variable from 5k to 95K. If it gets cold, it steps right up. After so many years of trying to deal with weather variations and a wood fired boiler, this is an ideal system.
Sooner or later, we will get clobbered with real winter temperatures.

coalkirk wrote:I don't have any tips for current hand fired boiler owners to deal with the mild weather.........

Open them thar windows!!!

That's what we do.

Cap has a good point, the mild steel will deteriorate if it is exposed to the hot fire. So I will suggest that you stack the firebrick right on the edge of the steel plate. Don't leave any steel exposed except the edge of the plate.

I've recently had my fire shut down and I cleaned the firebox. The edge of my blocker plate is exposed to the base of the coal fire. So far the steel looks to be in good shape.. However steel parts and pieces several inches above the grate have deteriorated a lot. I have steel retainers to hold the tall stack of firebrick in place, and these retainers are starting to look pretty bad. As long as I get a season out of them I'm OK with my design.

Finding Stainless Steel is not easy, unless you are lucky. Cap 'cheats' , he works with SS at work and can raid the steel scrap pile.!! I'm envious!

Take care, Greg L

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A stoker boiler or straight stoker is on my list... but it might be a few years until I can do that. Its hard to justify cost savings when you already have a coal burner.

I know this goes along the lines of the "how much are you burning" thread, but its relevant here. I’m burning around 50 lbs a day. I know you probably heat your domestic hotwater, but I’m curious, coalkirk and Yanche how much are you burning a day in this spring like weather, "idleing"?

I burn about 50 pounds a day. That's with the standard single set point aquastat. I estimate I would be 20 pounds less if I would get off my butt and install the Honeywell AQ475A.

Yanche

Yanche wrote: Forum member "ktm rider" has one of these AHS multi-fuel boilers and burns bituminous coal. Perhaps he would comment on his experience in this mild winter.
Yanche

Since I have a boiler and not a stove I just simply set my aquastat at a lower setting. While shaking only one grate like Yanche has described might work, I have a linkage handle on mine to allow me to shake all the grates at one time.
I have had my boiler overheat a few times from the mild temps outside. This was due to me not setting the Aquastat to a lower temp to match the higher outside temps.
If I set the aquastat at say 160 for the mild temps, it will shut off the combustion blower but the water temp will usually still climb about 10-15 degrees. it starts to dump heat when the water reaches right about 202 deg.
This happened to me late last night actually. My water was only at about 205 but it was super hot in my house. I had the aquastat set for the cold spell we just had at night time.
The wife is starting to complain about waking up sweating to death !!! I need to remember to set that darn thing down...

A Honeywell AQ475A Aquatrol Outdoor Temperature Compensator for Boilers would do it automatically.

Yanche

I already set my aquastat to 140 for all but the really cold weather. If there is no demand for heat, the boiler just runs its maintenance cycle which I have at the lowest setting. Runs for about a minute every 15 minutes just to keep the fire going.
I'm burning about 40lbs a day and that includes my domestic hot water.
The first three years, I ran it like my oil boiler at 180 degrees. I found through experiementing that I could burn it at 140 and still get the job done fine, saving alot of coal in the process.
I heat with a water to air heat exchanger and I use a tempering valve to moderate the temp in that coil to about 95-100 degrees. My circulator fan runs constantly and the house stays an even temperature througout.