OWB

[Bill]

I guy I know has an OWB and he was complaining to me how much wood it uses. He says it's a good unit, but eats wood. He uses 15 cords per year and he's in lower Wisconsin. That seems like way to much wood. His house isn't real big and it's insulated well. He said his water temp is 160*. Anyone got an opinion on why he burns so much wood? He also said they pour water in the center of the unit. I would guess this is some sort of heat exchanger. He didn't know much about the unit, except it uses recirculated water and it eats wood.

 

[pybyr]

I've heard of few OWBs that don't have a rather huge appetite for wood per amount of heat produced-- trying to do a slow/ gradual wood burn in the middle of a water jacket that keeps temperatures down just isn't much of a recipe for efficient wood combustion. The one/ only exception may be the wood-gasification OWBs, which seem to have emerged on the market only recently.

 

[heppm01]

So for those of us "stuck" with an OWB for now, what is the most efficient way to burn our wood? It seems our choices are a modest (but wood-inefficient) burn, allowing the water time to absorb the heat created, or a high-temp, fast burn (more wood-efficient) that unfortunately allows much of the heat to go out the flue. Which is the lesser of two evils?

 

[stee6043]

OWB's can benefit from thermal storage as much, if not more, than inside units. If room allows you could always plumb 1,000 gallons of storage in the basement and send the hot water from the OWB to storage. This way the OWB can run flat out, full tilt for a few hours and charge up the tanks. With a lot of the OWB's being massive with regards to heat output (300k??) you could charge storage quite quickly.

I know this doesn't exactly answer your question but peraps it's something your buddy would be willing to consider...

Regardless of the boiler you also want to make sure you're burning seasoned wood. You could potentially be doubling (maybe?) your wood consumption by burning the really wet stuff...

 

[Bill]

You have given some great ideas to share with my friend, and I do believe he burns some green wood, because he can, not that he should.

Thanks

 

[jebatty]

...what is the most efficient way to burn our wood?

Burn only well-seasoned wood, like you would use in a wood stove. Add storage as prior post states.

As you know, the OWB is inherently inefficient because the firebox is surrounded by water, the design does not allow full secondary combustion, and particularly does not allow gasification, which means a "cool" fire, lots of unburned gases and particulates (smoke), which = btu's, wood-cutting effort, and your hard earned $, going up the chimney to harass the neighbors and prevent you from building a retirement fund to allow you to retire at an age when you can enjoy yourself for many years to come.

 

[Eric Johnson]

I like Webmaster Craig's rule: The bigger the firebox, the more wood you're going to burn.

Having struggled for three seasons (prior to getting the EKO) trying to get more mileage out of an inefficient indoor boiler, I pretty much concluded that there's not a whole lot you can do to impact the amount of wood burned. The OWB manufacturers aren't stupid--if there was an easy/cheap way to make their boilers more efficient, they'd do it.

That said, there are several threads around here describing some of the things people have done to try to squeeze more usable Btus out of their OWBs. Things like extra firebrick and preheating combustion air can make a small difference.