Fire Box Reducer for A SF-260

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KTM250
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Post by KTM250 » Mon. Jan. 04, 2010 8:22 pm

Well now that I seem to have the boiler working pretty well (I can even keep it burning :) ) thanks to all the help of the forum members here. I was wondering what the advantages and disadvantages are in putting the fire box reducer in. Also is this something that I would use all the time or just in the warmer weather.
Thanks
Bob

 
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PC 12-47E
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Post by PC 12-47E » Mon. Jan. 04, 2010 8:52 pm

Hi KTM250, Good work on burning anthracite in the SF-260. 8-) With the shaker grates in the SF Harmans, you have lots of ways to reduce the fire box.

Click on this link.

Firebox on a Diet

PM me if you need more help. Ls Farm may be ready to take his AX to me again........ :D

PC 12

 
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LsFarm
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Post by LsFarm » Mon. Jan. 04, 2010 10:33 pm

Nope, I'm one of the original guys using a firebox reducer [at least on this forum] . My 'Big Bertha' hand fed SS boiler had a HUGE firebox, meant for logs up to 48" long. But for coal I shortened the firebox down to 'only' 22"x24".

I'm not sure you need or want to shorten the firebox in the SF260 boiler, didn't you at first have problems with not enough heat from the fire? I'd only recommend a smaller firebox if you can't slow the full size fire down enough to keep the boiler from overtemping..

Building a firebox reducer can be a bit involved, do you have metal working and welding skills?

Greg L.
firebox1.jpg

A tall SS/firebrick wall to reduce the firebox depth to 'only 24" '

.JPG | 273.1KB | firebox1.jpg


 
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KTM250
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Post by KTM250 » Tue. Jan. 05, 2010 11:54 am

PC Thanks for the link. Looks like some good Ideas there.
LsFarm I really believe that most of my problems were not getting the ash out of the bed. My guess is that it was retaining the heat in the ash and also not letting the coal burn properly. This caused the boiler to take a long time to heat up. Sense I have been getting the ash out, the temps come up faster and stay up. When the temps get into the mid 30s or higher the boiler just idles and it goes into overtemp. So from what you are saying and others from the other link is that this would be used for the warmer weather. I do not have metal or welding skills.

Bob

 
Joe in NH
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Post by Joe in NH » Tue. Jan. 05, 2010 10:05 pm

Bob - I am currently using the Harman firebox reducer in my SF260. I use the reducer throughout the heating season because the SF260 is somewhat over sized for my current heating requirements. If I remember correctly, you have a 2,800 square foot, newer, well insulated house. You very well could be in the same situation that I was in - a lot of heating capacity and no where to send the hot water. Having the ability to control my boiler when it was in the higher water temperatures was a particular concern for me and the firebox reducer allows me to have the smaller, more controlled fire I wanted. I do not have any appreciable temperature creep so the high end temperatures do not activate the dump zone. Now that you have mastered clearing the ashes form your firebox ( what I believe is the single most important skill in operating your boiler), you might want to think about a firebox reducer. Also, have you tried cutting back on the air through your idle port as a way of controlling temperature creep? Joe

 
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Cheetah
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Post by Cheetah » Tue. Jan. 05, 2010 11:46 pm

KTM250 wrote: So from what you are saying and others from the other link is that this would be used for the warmer weather.
Bob
The reason for using it at all is the limited range of efficiency for a hand fired unit. When it gets warm out and you don't need much heat you restrict the air getting to the fire to slow the burning down. But that results in some of the gasses not being burnt and some of the carbon being only partly burnt, giving off CO rather than CO2. So while you might be producing 1/4 as much heat you could still be using1/2 as much coal. Putting the insert in allows you to build a smaller fire that produces the smaller amount of heat required without starving the fire for air and thus burning more efficiently. The down side is that if it turns colder you are stuck with the smaller fire.

The down side to having a smaller fire is that you may need to work it to hard to get the heat you need. To get the same BTUs out of the smaller bed of coals you need to keep it hotter. To do that you have to be more aggressive about shaking the ashes down, with some partly burnt coal getting lost in the process. The higher temps also promote clinkers and the loss of heat up the flue. So working the fire hard causes efficiency to take a dive as well. And if you want to remove the insert to get more heat you need to let the fire go out just when you want more heat. That is why you wait for warmer weather before putting the insert in, if at all.

As was pointed out elsewhere, there are other ways to accomplish the same thing without the insert. If you want a smaller fire don't shake the ashes down so much. That leaves less room for coal like you found out before. It may work better if you poke at the center but not around the edges. That would give you a more centralized fire, almost like you would get by using an insert. But if it turns cold all you need to do is give it a good shake down to have a big fire back.

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