Outdoor Wood Fired Boilers

[BrianP]

Hello all

I hope this is posted in the right spot ....

Any experiences, comments etc., about outdoor wood fired boilers? Where I go deer hunting in northwest Michigan it seems lots of folk use them for heating.

They ain't cheap (C $10,000 or so) so I want to know as much as possible before going ahead. Wood shouldn't be a problem because I've got about 30 acres of woodlot and blow downs alone should keep the fires warm.

[Deerlope]

If you have your own wood and the time and equip to process it then they are a good deal. They like any kind of wood and green is OK too. I burn a lot of soft wood in the early fall then as it gets colder I switch to hard.

[Birdhunter1]

I use to work for a sheetmetal contractor and we had the Hardy Outside Wood Burning Furnaces that we would put in but they weren't our main line of equipment, just one of those things we had on the side if people wanted them. They are dependable and most parts are fairly universal (ie:controls, pumps, blowers, valves etc.). Installing them is not too complicated for anyone who has a good knowledge of electrical and plumbing experience. You will also need to trench in two water lines (to the unit and back to the builidng) electrical service (usually 110V) and a thermostat wire (most only need an 18-2 wire but I would recommend an 18-4 or an 18-8 in case one wire shorts out then you have an extra wire already buried and in place and all you would have to do is test the wire and then hook it up). All of these can be run in the same underground trench and you'll need to case them in something like a corrugated drain tile (I think that is what we used, but your supplier would be able to supply you properly). They are good sources of heat, and also the fire is outside so if it does get out of hand it burns outside rather than burning down your cabin. With the hardy you could add would once a day and keep it going, I'm not sure if or how much it would be different for your climate. You can also set them up to heat your domestic hot water, basicly all it costs is the price of your waterlines and maybe another pump (depending on brand/model). If you do go this route I'll help with any questions you may have in installation, service and such.
However: You said this was to be used at your deer hunting cabin. If you are not there to keep the fire stoked then you may want to look into something else, if the fire goes out the water in the boiler jacket will freeze and bust open thus ruining your heat source. You have to keep the fire going all winter long and anytime the temp is expected to drop near freezing (actually below freezing but the saftey factor considered I would go with near freezing, say 40, an expected 40 and below which may be common for NW MI?). So unless you will be around or have someone VERY DEPENDABLE you could have check it everyday I would strongly advise weighing your decision out. For this reason alone I would consider some other source of heat. If you go with a wood burner inside and have water in there you'll have the same kind problem/issue with freezing. If it is easy to get to I would consider an LP or Natural (if service is availabe) gas furnace and set the thermostat low when not there.

[llewellynsd]

The State of Maryland has made it illegal to own one of these stoves. Though I'm not always big on government telling land owners what they can and can not do on their land it is my opinion they did the right thing concerning these stoves. If I remember correctly the emission contain at least 33 know carcinogens. It is not the stove itself but how it is operated that makes them so offensive.

I have two neighbors that have them and during certain climatic conditions they fill the entire Valley with a thick blueish gray smoke haze. For sure a health hazard. And the efficently rating on these stoves are horrible. 20% is not good by any means.

My 2 cents.

Shawn

[ljh2]

When did MD make these illegal? My neighbor just had one installed last year. Can you point me to any supporting documentation regarding this? I was really considering installing one for my new house and shop at the farm in the next couple of years.

You mention the carcinogen emissions of burning wood. How many carcinogens are emitted in the production and consumption of petroleum products? Remember to include the drilling, transporting, and refining processes here. I can't honestly believe that burning wood - even at a slow burn - could be any less environmentally sound than burning fossil fuels.

[Pat]

To prevent an unattended wood fired boiler from freezing couldn't you just recirc some water through it from an electric or gas DHW heater?

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[egon]

I've always wondered why a glycol mixture and inside double heat exchangers wern't used.

Egon

[Pat]

There are a may ways to look at polution. Of those, one is global and another is local. None of my neighbors are refining crude. Oxygen starved lets-keep-the-fire-going-all-day-with-just-a-little-wood types can and often do stink up the whole region. In low concentrations, just a bit of wood smoke smells terrific (it is probably in our genes.) In dense choking layers it is an invasion, a tresspass, of my property and lungs.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[DirtPoor]

A good friend of mine built his own Outdoor Wood Burning heating system.

You note, that I avoid the use of the term "Boiler" since many state and federal regulation come into play when you heat water to a boiling temperature and produce steam, under pressure. A more correct term would be Outdoor Hot Water Heating System.

Although, not as efficiient as steam, hot water systems are much safer and ordinary hardware store complonents can be used and don't normally require any special skills (or licenses).

My friends system was built, by himself, about 30 years ago for heating a large open bay machine shop. The fire box was nothing special, just a brick lined furnace with a small blower in the door to provide an intial draft. The top of the firebox was as steel box with the water pipes and then filled with sand to distribute the heat of the fire without burning out the pipes. Someplace in the system there is a head/expansion tank. This type of system only attains a slight amount of pressure from the head tank and the water level is controled by a ordinary float valve with domestic water pressure being higher than the system pressure.

There is a circulating pump, with automatic control (thermostats, etc.).

The shop has a grid of 1 inch water pipes in the slab spaced every 3 ft. Zone control is achieved with a valve manifold.

The back up system is a electric flash type water heater and he just anded a commerial gas fired water heater. The electric system cuts in automatically if the fire goes out, however the gas system requires some valve twisting. The circulating pump can operate on an invertor/battery back up system for a few hour.

This sytem has operated trouble free for 30 years (although some of the back up systems have been added during that time period). My friend is now 78 yo and it is getting too much to cut and split fire wood so he is now relying on the natural gas system most all the time now. He how lives in a small portion of his shop since the heating and comfort are much better than his old house.

I hope this helps..

Steve

[Pat]

I knew a dog breeder in Ohio with hot water heat in his slab floor. It was a DIY sort of installation. Unfortunately he used copper tubing and it failed from chemical reaction with the concrete after several years. The moral of the story is to get some good guidance on these systems. The RPA (Radiant Panel Association) has an on-line forum (similar to CBN) where you can get good advice.

If the topography will allow you can consider a thermal siphon system where the energy to circulate the water through the floor is provided by the heat in the water with little or no requirement for pumping. This requires the heat source to be located lower than the panel to be heated (floor, wall, ceiling, whatever) so the heated water (from the heat exchanger) can rise up toward the heated panel by convection and the cooled water (after passing througn the panel to be heated) goes to the heat exchanger to complete the circuit.

A DHW heater is a terrific backup for those times when you may not want to fuss with or aren't able to fuss with wood.

Best of luck to you.

[img]/forums/images/icons/smile.gif[/img] Pat