Boiler Temp settings effect on wood consumption

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Tony H

Minister of Fire
Oct 24, 2007
1,156
N Illinois
Wondering if anyone has tested to see what temp setting is best to use minimum amounts of wood for a boiler.

I have an EKO 40 boiler and have been running for 3 seasons with good results system does not have storage.
I know alot of the sytems do have storage and would be burning full out heating the storage water.
In my case does the system run and use the least wood at the top setting 81C or does the sytem use the least wood when the temp is lowered to the lowest setting where it can still handle the house load with out excessive running of the forced air furnace fan to keep up.
I have read where some suppliers have told people to run at a lower temp in the summer when heating only DHW and thought it would make sense that if the system can keep my house warm at a boiler temp of 77 or 78C during the winter I might use less wood.
I don't have much on my system as far as sensors or recording and am wondering if any of you that do have experimented with this setting ?
 
I don't have hard data, but everything I've seen suggests that you'd get better efficiency running at lower water temps. This is a situation where you really want the smallest boiler that will just barely meet your needs so that it's not idling as much of the time.
 
So far, I find that the best way to maximize heat per unit wood is to not only keep the boiler out of idling mode, but to also keep a good bed of glowing coals for as great a proportion of the overall burn time as possible [coals dense enough that one cannot see the nozzle or bottom of the top chamber if you take a brief peek in the top door].

Once the bed of coals starts to go away, the unit may not be idling, and there may be some gasification going on, but in that mode the appetite for wood jumps and the net heat out per unit wood drops.

Guess that I did not answer your question on temperature, but my opinion, from the above, is that you'll need to vary the aimed-for water temperature, under different weather/heat load conditions, to keep in that 'sweet spot' where you maintain a dense bed of glowing coals as steadily and as long as possible without creating excessive boiler output.
 
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