HS TARM Wood Boiler

I do not have a Tarm unit but I am sold on the performance of wood fired vented "boiler" type stoves. The Tarm description of the draft and the high temp burn impress me as it would eliminate the smoke problem associated with most water stoves. Certainly the price of the Tarm is too high and I doubt that it will last a lifetime. I currently have a 14 year old Hicks waterstove and I know that it too will have to be replaced but I think I will build or have built the next one. The Tarm water storage capacity is not adequate IMO for the type application I have (3000 sq ft high ceiling 100+ yr old farm house) They offer an optional storage tank and that maybe the way to go. The ability of water to store heat for an extended period and to release it later as needed is the real benefit of this design system. I also prefer a LARGE firebox so that I can burn trash wood. A small gun burner from a construction heater can be added to a conventional waterstove chimney to act as an afterburner to burn the gases coming from the wood and clean up the chimney smoke. Many people try to burn a waterstove in the same manner as a wood heater. To me, this is a mistake. I burn mine as hot as I can until the water temp is elevated to near boiling then I shut the burn down and consume the heat stored in the water until the next firing. This creates a more efficient burn and avoids creosote buildup.

 

I have asked a few questions about wood burning boilers to this group before. I want to build my own, though. Someone suggested a book, "Ken Kern's Masonry Stove". I was lucky and found it at our local library - it's out of print. Agmanto is on the right track. The problem with burning wood is that you have to get the firebox real hot - 2000 degrees or so - in order to get the maximum energy from the burn and combust the creosote instead of depositing it on the flue. This means fast burn. Steel just won't do the job. Firebrick is lighter than steel but holds 5 times the heat. It allows the firebox to reach and hold the necessary temperature in order to get the most from the wood. Boilers that are part of the firebox or soak heat from the burning chamber make it impossible to reach the temperatures. Ken Kern suggests putting the water heating system around the flue. So an after- burner sounds like an improvement, if not a fix for a factory built boiler.
I went looking for firebrick this week. I found $2.50 each for new. Then I lucked into meeting a guy that had some leftover used firebrick. I got 300 for $45.
I need to size the water tank that I will build into the fireplace and then find copper to plumb it. How big are your water tanks? gobug

 

gobug, storage for a tight insulated 1800 to 2400 Sq ft in the 500+ gallon range and for the old farm house with high ceilings and marginal wall insulation and windows 1000 gallons.

 

Good Idea
The design idea, as already pointed out, seems much better for this outdoor boiler compared to others. The main part that makes this system work better is the remote storage tank (which any outdoor type wood boiler system should have and most don't). Keeping the water jacket temperature high and firing the boiler at higher temperatures is a step toward higher efficiencies and better operation (as mentioned).

Tank Sizing Example (better to get an experienced installer to help with this)
For example, useable water 1,000 gal x .70 (assume 70% useable hot water) = 700 gal, temperature drop 180 - 100 (maybe too low for some heating applications - verify) = 80 F degrees, heat available = 1.0 BTU/F*lb x 700 gal x 8.345 lb/gal x 80 F = 467,320 BTU stored.

If your house heat loss (at the outdoor temperature that you are investigating usually "1% ASHRAE Design Winter Temperature") is 50,000 Btu/Hr then divide this into the storage tank volume to find out how long you can go without adding more heat (wood). 467,320 BTU/50,000 BTU/Hr = 9.4 Hrs.

Good luck.

Alex

Heat Loss at Other Outdoor Temperatures
btw, if you calculate your heat loss at a design temperature and want to know the heat loss at other temperatures, the heat loss is directly proportional to the temperature difference between the outside and the inside. So you can figure your HL at any outside temperature easily.

 

I'm guessing this is a indoor wood boiler correct.For 7k you can get a dual fual unit with the shed on some of the outdoor boilers made.

 

Some people like to have there furnace indoors,I prefer not to have to fire my furnace more than twice a day even with the -20 below temps we have had, I can cut my wood up to 4ft long,no mess inside,takes about five minutes to load,as far as storage for wood it stays outside covered under a tarp.No flame or burning unit in house ins. companys prefer outdoor burners also.I have installed both types outdoor and indoor.

 

I have not seen a TARM unit but I do own a Central Boiler. One of the best features of the unit is that it is located almost 200 feet from the house. Keeps all the wood, bugs, dust, ash, flame, smoke, and filth outside. I don’t bother to cover the wood and I burn scrap pine and “trash wood”. The unit will take a 56” piece of wood, lumps, scarf cuts, stumps, roots or pallets cut in half. I fill it 2 times a day, once in the morning going to work and once coming home. The ash is a very fine power and I remove some ash every other week.
The unit does smoke when it first fires up but you can keep the smoke to a minimum by adjusting how much air the fan draft pumps into the fire box and by how you load the fire box. With a little know how my unit produces less smoke than the Vermont Casting Vigilant it replaced. Likewise, if you stack the firebox tight with a clip of fresh cut pine slabs, the thing will produce an awe inspiring cloud of smoke and steam that could easily hide a carrier group.
My unit is on its 5 heating year with no problems. I don’t think I would ever go back to burning wood inside my house or outbuildings. I do feel that the outdoor wood fired boiler is still in its infancy and that they will get easier and more efficient with time. I think TARM has some good ideas but it looks too complex for my tastes.