Outdoor wood boilers

Dave Yates (PAH)

On basic models and construction materials. For instance: stainless vs steel fireboxes and water jackets. We're receiving more requests for quotes as energy costs continue to soar and consumers looking for advice on which models are best.

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Some thoughts

AquaTherm is the most hydronic and radiant friendly of all the brands I have searched. Owned and operated by former Weil McLain and Wirsbo "wheels."

They do a good job of blending and offering all the right components and info. They also sell a PAP tube.

The Aqua Therm is a sealed pressurized tank. As such rust through issues are best handled, and connection to exisiting boilers is easy. They do use an inner stainless drum. Available sheltered or non-sheltered, which is nice for the build you own shelter DIYers.

www.aqua-therm.com

I'm looking at notching up the efficiency offering, also. I have an eye on some Euro gasification units that run out at twice the efficiency of the typical outdoor furnaces. Typical efficiency on those runs 40-45%. Euros claim 85-87%

Insurance and mortgage companies frown on indoor wood burning appliances around here. I'm building my first prototype of a gasification boiler sheltered and installed out doors. Hope to come out with the best of both worlds. Efficient, smoke free burning in a safe outdoor application.

Typically outdoor furnaces are sold and installed by the fireplace type shops, in this area. Not usually the best hydronicians, BUT, they work cheap Some will install in my area for $15.00 per hour!

I hope to distance myself from that crowd with better piping habits, and high efficient equipment.

Here is my prototype "drop and plumb" pad. A small 8X6 shed will be dropped on, then the boiler rolled into the building. Should have the building this week. I'll post progress reports.

Here is a Polish gasification brand I am considering. Check out the clever Ladomat protection valve and nice digital outdoor reset controls offered with this boiler.

http://www.eko-vimar.com.pl/angwww/aindex.html

Let me know if you need more info. The importer is not far from you and has a container load Stateside.

hot rod

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Christian Egli

I looked at a lot of these units at the ISH in Frankfurt. Europeans come up with all kinds of varieties. I have also asked a lot of questions to people who use wood boilers.

The ones I did not like:

Combined oil and wood unit, with no practical ways of preventing the half not in use of becoming a nice loss of heat up the chimney. Plus, if either side fails, it can't be replaced without scrapping the other, even if the other was never used.

Wood fire chambers that are directly in contact with the cold - water cooled - steel or cast iron wall make for very bad firing conditions. Making lots of soot and requiring daily, weekly cleaning of fire tubes. You can see the tar caking on in these units.

Don't like either the units that keep the draft closed to make the fire last longer on one load. These usually smoke a lot, white smoke, which is just a waste of unburned energy. This is a universal problem with steel and cast iron wall units.

I don't like a low roofed horizontal fire box, I prefer tall vertical combustion chamber.

What I like:

Fire chamber that is insulated with fire brick, that way the fire is hot and burn good and fresh wood ignites without delay. For wood, I think deep chambers require less poking and burn better.

Stainless steel chambers should be good as stainless is such a poor heat conductor. The fire should be hot enough, but it would not be as good as fire brick.

I like designs that extract the heat from the smoke after the wood is done burning. That means there must be some fire tubes or something beyond the walls of the fire chamber.

There should be two holes for admitting combustion air. A lower one for primary air at the level of the grate and an upper one, in the door leading above the fire for secondary air. The secondary air control is key to prevent smoke. The primary air controls the firing rate.

I was fascinated by the gasification models, some so fancy that I wondered if it made sense to make things so complicated. A lot of models, though, seemed like glorified wood stoves, but they all incorporated the features I like.

I like outdoor units, the mess stays outside. With the gasification units I would worry about CO emissions and would feel safer with an outdoor unit.

Hope this helps.

In your area, does it make sense to heat with wood if you have to buy the stuff? How about coal? I know wood stoves are great for getting rid of packaging and crating materials.

S Ebels

Hot Rod

I ran into problems with Aqua-therm here in jolly old Michigan. Seems they are not {H} rated as a sealed boiler and hence cannot be sold and/or installed as such. Two different mechanical inspectors caught these and made the HO convert the boiler to an open system. I can't remember if they were UL listed or not but you might want to check that also. I've been talking with Mr. Lunde from Dectra/Garn and I'm pretty impressed with what he has to offer. Mighty pricey unit though. A person had better be fully committed to alternate fuels before they buy one. The Garn will burn slab or cord wood, pallets, corn on the cob and wood briquettes and has been tested at over 84% boiler efficiency by Warnock Hersey.

Betz

Look At

Central Boiler or HydroFire...They are both the same unit under different names. I have one and it works very well, they have a lot of products for different applications and plumbing into your existing system. www.centralboiler.com

Dave Yates (PAH)

ISH

That was an impressive hall! Almost every booth had at least one live-fired unit with a central smoke/flue collection system snaking around the hall's ceiling. I barely had enough time to walk the aisles, but I'm planning on spending more time there in 05.

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