Outside Temps a Little Warm, House Too Hot

 
Ioldanach
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Post by Ioldanach » Tue. Nov. 29, 2011 10:30 am

I have a Coalbrookdale Darby, this is my first season using it. So far we haven't had terribly cold temperatures, but the Darby goes through around 40 pounds a day maintaining a slow steady burn, and a few extra pounds when I give it more are when the temps drop below freezing outside. However, on days like today when we're up in the 50's, it is burning at the lowest level I can keep it at and still keep a fire going and it is still giving us a little too much heat. I'm loathe to let it go out because the nights will drop and starting it up takes a couple hours, some wood, and about 40 pounds of coal just to load it up fresh.

I'm wondering if there's anything I can do to drop its BTU output when the days and nights are just a little too warm. Can I do something with firebrick to block off some of its burn space? If I cut the volume available for burning by half, will it take less fuel? Or am I stuck with just letting it go out and falling back on oil when the temperature fluctuations are too warm for coal for a few days.

I'm thinking that if I pull the high shaker grates and leave the lows (the ones that don't really move when I shake it) on the outside edges and stack some firebrick on them then I can reduce the fire's volume and therefore the coal needs when I don't expect to need the higher BTU's for a few weeks. On the other hand, I don't know if the stove itself needs to maintain a minimum temperature to prevent problems in the flue or draft.

I'm heating around 2,800 square feet, and the darby I think puts out 55k btu. I'm burning nut anthracite, the stove says it can take wood, nut or stove anthracite or bituminous.


 
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grizzly2
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Post by grizzly2 » Tue. Nov. 29, 2011 11:23 am

Welcome to NEPAcrossroads Ioldanach.

I am not familiar with the Coalbrookdale Darby, so hopefully someone who is will chime in and answer your question more definitavely. I know there are several members here who do block off part of the grates with bricks, sheet metal and ashes. They report various degrees of success. It seems that the configuration of the grates is the biggest factor in being successful blocking of part of them with any method. After all you still need to be able to eliminate the ashes in the half that is not blocked.

40 pounds per day seems like a lot of coal for a low fire in a stove with a max. output of 55K btu. Are you sure you cannot burn lower? What are your stove side and flue temps?

My Hitzer is listed at 50 or 55K btu, and I burn about 25 to 30 pound per day. I do have to make sure I am doing good shake downs and occationally rake the ashes from under the grate in order to maintain an adequate draft thru the burning coal. I lost the fire once this fall because I didn't shake down before bed.
I still have to open the window-stats at times to cool the house off a bit.

You are right, relighting the fire frequently would be a pain. Good luck and experiment a little with settings. A manometer is very useful in monotoring draft. Then you will know if you need to crank out more heat.

For more info about blocking off and raking the ash, do a keyword search by topic. :)

 
Ioldanach
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Post by Ioldanach » Tue. Nov. 29, 2011 11:52 am

Well, the firebox is 22" wide by about 12" deep, and I typically fill it 6" high with coal. The stovetop temp was about 330-370 degrees and I don't have a thermometer on the flue. I don't trust the thermometer's calibration 100%, and my infrared thermometer died recently. And I need to get ahold of a manometer. I also don't have a barometric damper.

You can see the old ad as a pdf.

I'm still new at this, though, and I'm probably not firing it as efficiently as I could. I'm still learning. A quick calculation says 25Mbtu/ton, burning at 40 lbs per day translates to 21Kbtu/hr, which, ignoring losses, would imply that I'm firing it at roughly half capacity. Which means I must be able to fire it lower than that, I'm just not familiar enough with the settings yet. Though this also means I can expect to go through 100 lbs a day if I'm running at full tilt. Does that make sense?

On the plus side, my wife is in love with the stove, this is the first winter she's been comfortable in the house. We usually keep the thermostat down to 67 to save on oil, 62 at night, and the temps have been at least 70 degrees downstairs and 75+ upstairs most of the time. And even when the indoor temps get down to 67, which they did last week, it feels warmer than 67 with oil heat did.

 
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Post by lowfog01 » Tue. Nov. 29, 2011 12:23 pm

The idea of using the lower grate to reduce the firebox makes sense to me. A lot of members do that in the fall and early spring. You'll have to find a way to get some air through the ash since the lower grates don't move much or any. Is that right? The ash build up will act as a damper further reducing the fire. Do you have a poker that will fit between the bars on the grate? If so, you maybe able to clear enough ash to get the air through but not enough the fire takes off. Your local hardware store can put a handle on a 14 rod for you if need be. Some folks even bend the rod 90* so they can clear the grate better.

I say do it! If it doesn't work and the fire goes out, so what? that's where you are now. If it works, Wahoo! Let us know how it goes. Lisa

I see that from you last post that your stove top temp is 330-370. That's pretty high for a stove that's burning as low as you can get it without losing the fire. How did you determine that? I know when I first started I thought my Harman couldn't possible go below 300* but when I had a day to really watch the stove and play with the air intake I discovered that I can burn it at about 125* stove front before I start to lose the fire. And losing the fire takes a really long time. Long enough I can respond to the stove's needs before it does die. Now the first thing I look at when I get home from work is the stove front thermometer. If it's at 125* I know my fire is ok. I also have room thermometers so I can monitor the heat distribution and tell if something is wrong with how the stove is set.

Hey on the bright side - I heard it was snowing in Memphis this morning so the colder weather must be heading our way. Good luck, Lisa

 
Ioldanach
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Post by Ioldanach » Tue. Nov. 29, 2011 12:35 pm

No, it isn't two levels of grate, it is a series of bars with knobs all next to each other. The lower/upper refers to the position on the shaker bar, the lower ones have a little short dimple and sit very low on the bar and the upper ones are tall. When you pull the handle back and forth, the bar pivots and the upper grates move back and forth a lot while the lower ones move back and forth only a little, if at all. So if I remove every other bar from each edge for the width of a firebrick, then I can sit the firebrick on the bars that don't move much, and I won't have them being rubbed against the grates when I shake it down.

I think I need a barometric damper, I might have too much draft to pull it down much further than that. I have two 'dials' on the front as air intakes that can go from fully closed to three turns open. At three turns open and a full load of coal the inside front grate in the attached image will start to glow a dull red and the stovetop will run at about 500-550. I haven't let it run very long like that, though, so I don't know how hot it would climb if I left it there. The 350-ish degrees was measured when they were each a half turn open. The lower door also doesn't have a gasket so I bet even with the intakes fully closed it lets in just enough to keep the fire going.

I think I need to play with it some more this weekend.

 
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Post by Ashcat » Tue. Nov. 29, 2011 12:56 pm

What I do when we are going through warm spell is to shake down like normal, then carefully and neatly pile about 10 or 15 pounds of coal in the very center of the firebox. This leaves a neat little mound in the center of the firebox, and any peripheral fire remaining burns out with an hour or so. After I make the mound, I give it plenty of air to make sure that the bottom of the mound is burning, then I shut down the air intake almost completely. That small pile of coal continues burning at least 15 hours or more in my stove, as long as the air intake is dialed way back. Stove temperature goes way down, so much so that I can indefinitely rest my hand on the top of my stove.

If the next 12 to 15 hour stretch is also going to be very warm, you can keep up this process indefinitely: after livening up the fire real well, shakedown as normal. This will spread out the pile of burning coal, upon which a new 10 or 15 pound pile can be piled.

If, on the other hand, for example during a cold night, you need to have a full firebox of burning coal from time to time, after shakedown simply load the stove as you normally would. Allowing this plenty of air for an extended period of time will allow all of the peripheral new coal to catch, and fairly quickly produce fire in the entire firebox.

One other aspect of this technique that I appreciate is that having no fire in the peripheral parts of the firebox means that I can poke and shakedown any ash that typically hangs up on the edges of my firebox, that is difficult to remove completely at shakedown with normal stove operations.

From the looks of your stove firebox, it seems quite likely that you could use this method. This also has the appeal of requiring no modifications to the stove, such as adding firebrick to the firebox floor, shaking down only part of the firebox, or other similar techniques.

 
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Post by buck24 » Tue. Nov. 29, 2011 1:45 pm

I would have to agree with Ashcat on the way he burns on warmer than normal temperatures for this time of year. I use a very similar method. I mound up the middle of the firebox with coal and have less coal on the sides. Your coal consumption will be less and you should be able to keep the fire going without baking you out of the house. When it gets cold out again you fill the sides up higher and add more coal and we're back in business. You have to take some time to learn your stove and see what she can do.


 
Ioldanach
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Post by Ioldanach » Tue. Nov. 29, 2011 1:50 pm

What happens to the sides of the pile? If you shake it down, won't the ash fall through and leave the sides of the mound exposed?

 
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Post by franco b » Tue. Nov. 29, 2011 2:03 pm

Ioldanach wrote:What happens to the sides of the pile? If you shake it down, won't the ash fall through and leave the sides of the mound exposed?
As ashcat stated, when shaking down it tends to spread out the center pile of coal. Well worth a try. Make the mound as high as possible.

 
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Post by Ashcat » Tue. Nov. 29, 2011 3:13 pm

franco b wrote:
Ioldanach wrote:What happens to the sides of the pile? If you shake it down, won't the ash fall through and leave the sides of the mound exposed?
As ashcat stated, when shaking down it tends to spread out the center pile of coal. Well worth a try. Make the mound as high as possible.
Yes, the pile flattens out--then just make a new pile with fresh coal on top of the burning coals remaining. A higher pile is good, but you can vary this depending on how long you need the low fire and when you'll be able to tend again.

 
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Post by Ashcat » Tue. Nov. 29, 2011 8:24 pm

Here are two pics of today's "mound", nearly 15 hours after loading it, after I livened the fire in preparation for shakedown and reload.

With and without flash:

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Ioldanach
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Post by Ioldanach » Wed. Nov. 30, 2011 11:45 pm

I started off by just trusting in the coal's ability to keep going with almost no air. I topped it off with coal, tamped the top down as I'd seen suggested in another thread, and dialed down one intake to closed, and the other to only one half turn. In the morning, the top inch or so of the coal was still unignited and black and there was a healthy glow at the bottom. Opening up the intakes had it pushing 8" flames in 15 minutes and ready for a second load. Two loads into the process I've used only about 20 pounds in 24 hours and the house is at a reasonable temperature.

 
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Post by SteveZee » Thu. Dec. 01, 2011 9:42 am

Looks like you've got it under control now. The Darby is a great old stove. Some were made with little boilers in the back of them that could be hooked to radiators. There are a few improvements that could be made like a larger ash pan but they are a very handsome stove and pretty good size piece of iron. Best of luck with it.

 
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Post by Ioldanach » Thu. Dec. 01, 2011 9:46 am

Yep, I think I'm getting it. Though last night we did go through almost 20 pounds of coal over a 12 hour period, but temps dipped to 30 degrees overnight. The grass was crunchy this morning.

 
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Post by kstills » Thu. Dec. 01, 2011 10:39 am

That's a pretty stove you have there. :)


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