OWB design. More water? Less water?

[Timber_Hitch]

OWB Burning Efficiency

Hi Team , I have been burning for 10 years and have installed 8 of these wood boilers for friends. They mostly chose Central Boilers but one was a Tarm and a Shaver, and 2 were the new ECO one out from Central Boiler. Let me tell you this the new ECO boilers burn real clean once they are up to temperature but there are some big drawbacks. The wood needs to be split smaller and the heater needs to be fed every 8 hours or so. This new heater has a bypass when your sarting up so you dont choke the fire out. If he waits to long to load he needs to start with the small pieces of wood again. This ECO heater requires more cleaning,more loading,more wood splitting,and very careful wood placement to prevent damaging the smoke reburning chamber inside these units. My heater is a Central Boiler HF-60 and with a full load of beech I get a 4 day burn time in the average winter temperatures and a 3 week burn time in the summer just running the hot water through a 19 plate heat exchanger. I kinda like less work by using the traditional units. If I burn small loads 1/8 th full of dry wood the unit will smoke a very little for about 1 minute then burn clean as any of them. But this method requires way to much babysitting. So what are your thoughts ? O the Colorado fires have just put more smoke into the atmosphere then all the stoves in the US times 10 years. perspective

 

[leon]

OWB design

How cute and clean and hot and stuff of a little fire it is means nothing to me.

How long a burn time and total wood consumed each burn cycle does.

My carbon footprint is likely smaller than average but you go ahead and lose

enuff sleep over it for both of us.

I do not lose any sleep over how efficent my boilers combustion chamber is because it is half
full of firebrick for the reasons stated previously.


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It has never been a case of cute clean and cuddly with boiler efficiency in any case,

Industrial boilers and incinerators use a lot and I mean a lot of firebrick to insulate the
combustion chamber to keep the fire hot and to burn clean with almost no smoke.

high quality firebrick is magnet for heat and sheds ot slowly back into the boiler when
it is not absorbing heat.


The firebrick is transfering heat to the boiler walls as it is shedding heat in a controlled
release because of the dense mass of the fire brick itself.


If an owb is lined completely with firebrick it becomes a heat sink because the firebrick is
absorbing the heat generated by fuel load and combustion air and the firebrick is absorbing
this heat and shedding it to the boiler walls in a controlled manner preventing cavitation corrosion
from hot spots which will ruin a boiler or furance wall.

Just as an example, an air to air furnace will fail from pin hole air leaks from the act of combustion over time
as it is not completely lined with firebrick.

 

[CTYank]

Some of the most efficient boilers made were designed by Mech. Eng. Professor Richard Hill, UME Orono.

Totally separated wood combustion chamber, wrapped in insulating refractory. Hot gases then passed through heat exchanger to heat water. Typical storage 500 gals. See Hill's Furnace for more. Dr. Hill also designed other interesting, efficient wood-fired heating systems.

The concept is simple, really:
Short, intense fire at very high temps, some estimate 3000 deg F (very clean burn),
Heat exchanger to extract heat from exhaust to water,
Heat stored in tank sized so burner could be run for short period/day in northern New England.

Some of these ran for many years, until passages got clogged with ash, because later home-owners were ignorant about cleaning the slow accumulation of fly-ash.

Boilers smoldering wood in a big water-jacketed (cool) firebox are a pollution point-source. Bad idea. Bad P.R.
Much of what's been written here is seriously ill-informed IMHO.