What I Learned From Heating with An Outdoor Wood Boiler

This post was originally published in December, 2017 but we thought it appropriate to re-share on this cold, snowy day. If you have a wood boiler, reach out to our resident expert, Ken on Facebook for tips and advice on how to stay warm all winter long.

By Ken Farabaugh

Heating Stonehurst with an outdoor wood boiler

To heat our showroom, we're using an E-Classic 2400 Central Boiler which we purchased from Dale Temple of Temple Plumbing & Heating in Westminster, Vermont. We burn scrap wood (from furniture making) and trees that need to be culled from our forest.

Heating Stonehurst Sustainably

My wife, Peggy, and I started a sustainable furniture company in 2005. The business has grown over the years and in September 2012 we purchased Stonehurst, a historic property and former ski area in Vernon, Vermont. The goal was to restore the property and create a unique destination for customers to shop for Vermont made wooden furniture. We decided to invest in an outdoor wood boiler to heat the renovated property. Peggy wanted to avoid using fossil fuels and I wanted to make use of the property's many downed trees.FireStar XP wi-fi module | Outdoor Wood Boiler

We opted for the FireStar XP wi-fi module which provides real time performance, operational data, charts and graphs over time. I've also set up texts & emails to alert me of potential problems.

Outdoor Wood Boilers Have Come A Long Way

Outdoor wood boilers have become very efficient and the technology has evolved significantly in the last decade. They can burn almost any kind of wood (except chemically treated). We have an E-Classic 2400 Central Boiler with the remote monitoring module option, purchased in December of 2012. Now, with ~ five years experience under my belt, I felt it was time to share our experience with others who may be considering a boiler. I’ve also mixed in a hands on class in forest management as that is key to our strategy (and probably yours too).

No Smoke | Outdoor Wood Boiler | Vermont Woods Studios Surprisingly, there's rarely any smoke with our boiler.

The Benefits

  • In Vermont heating fuel is accessible and plentiful.
  • There is no indoor mess.
  • There’s hardly any smoke. The boiler is so efficient that you typically cannot tell it’s running unless you see the heat waves emanating from the stack.
  • Outdoor wood boilers include an option that allows remote monitoring capability that will email or text you if there is any problem. You can monitor boiler performance on your iphone to see when it’s time to throw in additional wood.
  • Boiler ash is minimal during colder weather when the boiler is running hot. During milder conditions the boiler runs slightly cooler and results in a higher amount of ash accumulation.
  • We can fill the firebox with wood that is cut to 30 inches allowing 3 inches on each end for air flow about 10 times before cleaning the ash out. The amount of ash is typically about 2 shovels full.
  • You will smell like smoke after you load the boiler...lol, if you like that aroma.

Remote monitoring provides the peace of mind that the boiler is operating as designed. I can see water and reaction chamber temperatures, burn time and furnace mode in real-time with my iPhone.

The Challenges

  • You will smell like smoke after you load the boiler
  • Understanding how to maintain boiler water chemistry. It’s important to prevent corrosion of piping and components. It's not difficult but you have to check the chemistry at least once per year or after adding additional water.
  • Any type of wood can be burned in the outdoor wood boiler, however there is a downside if the wood is soft like pine or hemlock, which is creosote buildup in the air inlet penetrations.
Softwood & hardwood trees at Stonehurst - both are used to fuel the outdoor wood boiler We're trying to clean out some of the softwoods on our property to allow our native hardwood seedlings to thrive.

Boiler Basics

A few notes on how most outdoor wood boilers operate:

  • The boiler cycles on and off to maintain boiler water temperature between 170 and 185 degrees F.
  • The wood that burns results in a coal bed. The hot coals drop down into an area called the reaction chamber which acts like a blast furnace, resulting in gasification of the wood that is further burned.
  • The combustion air for the firebox is supplied by a fan that pushes air into the firebox through solenoid operated penetrations.
  • Typically, there are two penetrations approximately 2 inches in diameter that operate independently based on combustion air temperature being supplied to the heat exchanger to heat the water.
  • When softwood is burned these penetrations develop a creosote and begin to plug. They will require periodic cleaning and the frequency will depend on how much softwood is being burned.
American Tree Farm Certification

Our professional forester Lynn Levine convinced us to get American Tree Farm Certification. ATF is an independent third party that ensures we follow 8 important standards of sustainability on our land. Good forest management demands harvesting wood strategically so we have a constant source of fuel.

The Economics of Forest Management

  • We’re managing our forest with the goal of increasing hardwood yield, so softwoods (ours are pines and hemlocks) need to be removed in order to open the forest canopy & allow hardwood seedlings to flourish. We are fortunate to have our professional forester, Lynn Levine, managing this.
  • You need to have logging equipment for tree removal in the woods (or you can hire a logger).
  • For tree removal to be profitable for the logger, there needs to be enough saw logs to justify moving the equipment on site. This will require walking the forest and marking trees so the logger knows what to cut.
  • There is obviously some work involved with cutting, splitting and stacking wood. You will also need to be proficient at chainsaw operation and maintenance.
  • A log splitter is essential but if you lose focus for a split second it can cause serious injury. The log splitter is very unforgiving. You should never be in a hurry while using a log splitter (I lost a finger to it).
Stonehurst Furniture Showroom | 5000 sf | 12-16 Cords of Wood We go through about 12-16 cords of wood each year, depending on the winter weather-- that's heating about 5000 sf in our showroom at Stonehurst.

Make Sure Your Wood is Dry

The wood you use will determine boiler efficiency and it must be good and dry. We have learned to maintain 2 years of wood inventory. Covering the top of the stack of wood with plastic helps the drying process. The wood stack needs to have good airflow around it and about 2 years of time to allow significant drying which will limit the amount of periodic cleaning of the combustion air inlet nozzles.

The Firestar control panel | Vermont Woods Studios

The Firestar control panel shows water and reaction chamber temperatures as well as internet connectivity.

Maintenance Issues

There are certain critical components that, if they fail the boiler will cease to supply heat and it is wise to inventory these parts. These parts include: door gasket, boiler circulating pump/motor, one spare solenoid, reaction chamber temperature probe and a water temperature probe.

Our showroom and offices at Stonehurst occupy about 5000sf. We use 12-16 cords of wood/year for heating.

Our showroom and offices at Stonehurst occupy about 5000sf. We use 12-16 cords of wood/year for heating.

Tips & Advice

The outdoor wood boilers of today utilize advanced gasification technology that enables high efficiency. If you have an available wood supply and the equipment, or a couple robust teenagers to do the cutting, splitting and stacking, or you like using a chainsaw, or if you just like the exercise, it is a good way to provide building heat.
I feel it is better to default larger than smaller as far as boiler size is concerned. The bigger the box, the bigger log pieces you cut, the less cuts for more fuel. Cutting, splitting and stacking wood is fun! Think Tom Sawyer….. Stay warm and safe out there!

2018-19 Season Wood Boiler Update & Challenges

Well another heating season is almost behind us!
This winter on a cold day (15 degrees) in December between Christmas and New Year’s the outdoor boiler began tripping the 15 amp GFCI boiler supply breaker in the main building. The GFCI was able to be reset, however intermittently continued to trip the breaker about once per week. Nothing could be found on the main heating distribution panel or at the boiler.
On February 7 the GFCI tripped and current readings were taken on all three zone pumps as well as when the electronics were powered up. Below are the readings:

  • Circuit power up - 0.245 amps
  • Total with Zone 1 pump running - 3.64 amps
  • Total with Zone 2 pump running - 4.26 amps
  • Total with Zone 3 pump running - 5.24 amps (well below the 15 amp rating for the GFCI)
On February 12, the boiler lost power and this time the GFCI would not reset. Because of the previous investigations, the focus became the boiler outside.
Power Supply for Boiler Elements
A new remote monitoring module had been installed earlier in the season after the remote monitoring digital power supply failed in October, therefore all the connections were being inspected. Inspection revealed a connection on the fan that was heat damaged. One of the three wires on the plastic connector was deformed and blackened more so than the others. Due to the nature of the environment a black dust coating of this enclosure is not uncommon, so everything had to be wiped down to see it.
This connection was apparently intermittently spiking the differential current that the GFCI was sensing. There was also some line work going on nearby the power company that could have been impacting line voltage intermittently, exacerbating the issue.
Fortunately I had a spare fan that we could install. The old fan was unplugged and the connector cleaned up as best we could and the new fan was installed. There was nothing wrong with the fan itself, it was simply a high resistance connection that overheated the connection and caused the differential current condition and subsequent breaker trip.
Replacement fan for wood boiler
The Central Boiler Classic manual tells you at the end of the heating season to lubricate this fan with some 3-in-one oil on the motor side and you have to remove it to do that which involves unplugging that connector. I am theorizing that in the process of unplugging that connector, one of the wires became slightly dislodged or loosened, causing the high resistance connection. It is now March 28 and no additional problems noted.
If you read my initial boiler blog I highlighted the importance of having some critical spares. At 15°F outside, this is a reason why critical spares are important when you are relying on an outdoor wood boiler for the majority of your heat.
Happy heating!

Stop by & See if an Outdoor Boiler is Right for You

I'm not getting paid for this-- I just really like the boiler and want to reach out to others who may be considering one. Feel free to stop by Stonehurst and check ours out.

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Peggy Farabaugh

She is a CEO who brakes for salamanders, has bottle-fed rescued squirrels and spent her vacation building furniture for a rural school in Costa Rica. She believes in the future and in the people who will build it. A former distance-learning professor at Tulane University with a master’s in environmental health & safety, she turned an interest in forest conservation and endangered species into a growing, local business. She delivers rainforest statistics at breakneck speed, but knows how to slow down and appreciate the beauty of a newly finished piece of heirloom furniture.

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    Years in Business

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    Trees Planted

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    Happy Customers