Outdoor wood boilers

Simply Rad

I have a new shop/caretaker unit beginning this fall. The project will be radiant infloor heating with the primary heat being a LP boiler and when the owner is onsite he will use an outdoor wood boiler. The last wood boiler I installed was a Heat Master G series gasification boiler. The owner is happy with the unit but I am just checking to see what others like for equipment. I normally install Viessmann but they do not currently have a wood boiler available here in the US. This is a high end project and I would like to provide quality equipment. Thanks for you feedback

Regards

Jeffrey

GroundUp

As far as an outdoor gasification unit is concerned, it's pretty tough to beat a HeatMaster G series in my opinion. The Pristine series from Crown Royal is a great unit as well, but I have run across quite a few with poor refractories and bad welds from the factory. Personally, I'm less than impressed with the way Crown handles their warranty issues and for that reason, I place HeatMaster in the top position. Not to say I haven't seen issues with their units as well, but customer service is second to none in my experience. The Central HDX series have some very happy customers, but they have a lot more unhappy customers from what I've seen. Warranty is completely nonexistent, and peak performance comes at the cost of <15% moisture content fuel along with thorough weekly maintenance which is typically not what a wood boiler operator likes to do. Portage and Main & Polar come from the same facility under different names, both mild steel compared to 409 stainless for Crown and HM (and a crappy mild welded to stainless hybrid from Central), also with a taillight warranty and almost zero dealer support as they like to sell factory direct and have lost the majority of their dealers because of this.

With all that said, occasional use is NOT the place for any gasification unit. The constant condensing and expansion/contraction will have the tubes gummed up continuously. Even a conventional unit suffers from issues in this department, but they are also federally outlawed in the United States since 2016 when used for any non-commercial space. If this part-time use is a necessity, it'd be best to keep the unit at a relatively steady temperature at all times. Whether that means burning LP to keep the water jacket warm at all times via constant circulation, or moving the unit indoors to a conditioned space, is up to the end user and their insurance company. The G series is actually UL listed for indoor use if desired, but an indoor unit also opens many doors to other units such as Frohling or Tarm.

psb75

Tarm mfg. is no longer in existence. Frohling is. I would discourage outdoor wood boilers for the reason mentioned: they are banned. I'm not sure that folks that have gasification units are well-trained to use ONLY really seasoned/dry fuel—which is a requisite of gasification units. This is true also of indoor gasification units. Fuel management is a hard "nut to crack" for anyone using cord wood. In which case pellet boilers are a good alternative. All solid fuel burners need to have heat storage tanks as a component of the whole system, for best efficiency.

Jamie Hall

Heat storage tanks are not only for efficiency with those things. They are also needed as a dump zone for when (not if) they run away.

GroundUp

https://forum.heatinghelp.com/discussion/comment/1804812#Comment_1804812

Only conventional units are banned. There are something like 15 outdoor gasification models with current phase 2 EPA certification, which were mentioned earlier. Nothing banned about them.

GroundUp

https://forum.heatinghelp.com/discussion/comment/1804819#Comment_1804819

EPA certified outdoor units all have onboard storage, and are unpressurized which does not require a dump zone of any sort.

psb75

Dump zones are required for indoor solid fuel boilers. Maybe exceptions for cordwood and pellet boilers that are dependent on combustion fans and metered fuel-feed augers.

leonz

https://forum.heatinghelp.com/discussion/197344/outdoor-wood-boilers

I guess most of this decision is going to depend on whether your client can purchase western Lignite coal, Western Sub Bituminous Coal, Bituminous coal or Eastern Anthracite coal or cord wood.

Alternate Heating Systems offers an outdoor coal stoker boiler that can be loaded with a front end loader or skid steer loader. The AHS coal stoker boilers can burn Western Sub Bituminous Pea Coal with no smoke and provide plenty of heat and loading it every few days and shoveling out the ash bin.

If Eastern Anthracite coal is available it provides the greatest amount of heat per pound with no smoke and very high energy efficiency per pound.

The Alternate Heating Systems, Axeman Anderson, EFM DF50 and keystoker would need a simple hoop shed with a solid end wall for a small diameter flue thimble and flue pipe.

Western Sub Bituminous Coal is less than 10 dollars a ton picked up at the mine and creates very little coal ash and creates a great amount of heat per ton of Sub Bituminous Coal and the rolling grate AHS and Axeman Anderson stokers can burn it.

A coal stoker boiler can be paired with a very large hot water storage tank in an open system in the same hoop shed to create huge amounts of hot water for heating and domestic hot water with a circular or trombone style Domestic coil depending on the brand of coal stoker boiler purchased.

A surplus 8,000 gallon insulated railroad tank car and a small coal stoker boiler can provide the user with 8,000 gallons of hot water for heating and provide huge amounts of thermal mass for space heating.

A concrete support system would be needed for the tank cars body.

Now if you still want to deal with cord wood you have the option of using a commercial Garn wood boiler with its induced combustion 2-3 pass heat exchanger and very large water volume. It is also designed as an open to air expansion system.

A Garn boiler like the others requires very dry wood and would need to be loaded several times per day with small loads of very dry wood.

A Garn boiler would need to be placed in a separate building and insulated or a very large area in an existing building that is insulated.

The flue gas exhaust of the Garn boiler is essentially a mixed steam flue gas vapor when it finally exits the very small flue pipe through the wall of the building.

Simply Rad

thanks all for input

The owner will be using the “man cave” most weekends, as the property is 30 mins from his primary residence. The property is in NW Colorado and surrounded by national forest.
Most of the species of wood will be fur or pine and very dry. He can use aspen, which burns very hot to start fires.

hot_rod

I bought indoor gasification units and had small Tuff Shed buildings built to house them,many more options that way. Keep some wood inside also.

I think you want at least 250 - 500 gallon buffers for good long hot burns. That is the best way to run a gasification boiler.

I started with 160, then 300, finally ended up with a vertical 500 and things worked perfectly.

Repurposed LP tanks are the least expensive way to get large pressurized vessels fo buffer tanks, or the well insulated unpressurized tank that Tom sells. At American solartechniques

There is a learning curve to burning high efficiency units, lots of maintenance required to keep them running at peak efficiency. What about hardwood in your area? Seems like beetle kill pine is the predominant fuel😗

Generally a 500 gallon buffer does not require a dump zone, it can usually absorb a burn down from a quick shutdown gasifier.

I’ve spent a lifetime playing with solar thermal and wood fired boilers, be glad to offer an opinion.

psb75

Good fuel acquisition and management of it (i.e. burning dry wood below 20% moisture) and then good combustion (hot and efficient) with that heat energy stored in large volume tanks (pressurized or non) and then distributed well is quite an undertaking—not for the unintelligent or lazy person. Do your homework. Design well. Utilize your indoor space well, get good equipment and install it properly. Hot_rod has good ideas about this subject.

Robert_25

https://forum.heatinghelp.com/discussion/197344/outdoor-wood-boilers

what is the plan for keeping the outdoor boiler from freezing when the house is unattended?

Simply Rad

Robert. The wood boiler will have a glycol mix in it. There will be an LP boiler to keep things warm when the owner is not there

Simply Rad

So I have had the conversation with the owner about keeping the wood boiler warm. The builder and I discussed a outside shed attached to the garage with heat tube in the slab under. The question now is how warm to keep the outside wood boiler when the owner is away during the week. Remember the owner with be at the "compound' thurs/friday-sunday most weeks

Thanks Jeffrey

Robert_25

Wood boilers are generally poorly insulated. Keeping it warm with LP will be like heating a poorly insulated outbuilding.

Simply Rad

the shed we build for the boiler will be insulated with a door up to modern codes.
earlier responses were concerned about allowing the wood boiler to cool off during away periods with no fires.
thanks Jeffrey.

leonz

NOPE, NOPE, NOPE, not going to happen unless you install a massive amount of water to keep it above freezing

by using a huge surplus bulk milk tank or a surplus insulated 8,000 gallon tank car minus the trucks and wheel

sets to have this amount huge amount of thermal mass to use.

Simply Rad

the slab heat will keep the shed above freezing. The wood boiler also holds 234 gallons of fluid.

hot_rod

what size will the shed be?

You need a heat load on it to see how many btu/hr to maintain 45F in that space.

Add a small gas, lp, or electric back up heater to maintain the room temperature

Or a super insulated thick slab to store 5 days of warmth for the shed.