How Outdoor Wood furnaces Work and FAQs

How do Outdoor Wood Boilers (Wood furnaces) heat my home?
An outdoor wood boiler also known as an outdoor wood furnace is a heating appliance that sits outside the home while providing heat to the home. The boiler is a wood fired combustion chamber that is surrounded by a water jacket. The water in the jacket is heated and pumped underground through insulated pipes to the home that is to be heated. Inside the home, the heat is put into the existing furnace via a heat exchanger and into the water heater via 2 methods, a water pre-heater and/or a side-arm attachment. Once the heat is used, the cool water is returned to the boiler to be heated again. This cycle occurs over and over as the heat demand increases or decreases.

Is the Outdoor Wood Boiler (Wood furnaces)  safe?
The boiler is located a safe distance from the home.  It is constructed of 1/4″ steel. There really is nothing in the boiler to burn but the wood you put it. It keeps the fire out of your home yet you feel the warmth inside.

Can an Outdoor Wood Boiler (Wood furnaces)  “blow up”?
The simple answer is No. Many ask this funny but legitimate question.  The boiler is open vented meaning that there is no pressure to build up.  There are no components that can “blow up” or explode.  There are two open vents on the boiler.  These should never be plugged or resticted in anyway.  These open vents is what keeps the boiler from building pressure.

How much wood will I use?
This is a very good question and our consultants can help you by looking at your old utility bills and give you an estimate based upon our BTU Conversion Calculator.  This formula is an exclusive product of Wood Boiler USA.  We believe it is very accurate.  Do not believe a dealer or salesperson who believes they can tell you without knowing how much energy you used in the past.  Ask for us give you an accurate estimate.

Why is it called an Outdoor Wood Boiler (Wood furnace) ?
The name is a little misleading as it does not actually boiler water, it heats it to a safe 150-185 degrees. Water actually boils near 212 degrees. Our wood boilers allows the user to adjust the temperature of the water to your preferred level. For instance, during the summer, we recommend you leave the temperature at 153 degrees and during the winter we recommend you adjust the temperature up to 185 degrees.

How does the Outdoor Wood Boiler (Wood furnace)  control the temperature of the water?
The wood boiler’s burn chamber is surrounded by water. When the temperature drops below the setting on the thermostat the automatic air induction system activates and burn chamber is inducted with air.  This air forces the fire to ignite and heat is produced. Once the turn-off temperature is reached, the induction system disengages and the fire returns to a near dormant state.

Can an Outdoor Wood Boiler (Wood furnace)  heat my pool and/or spa?
In our history, you will see this was one of the challenges we wanted to address. The simple answer is Yes.  Using a liquid-to-liquid heat exchanger, we found a solution. There are multiple types liquid-to-liquid heat exchangers available.  When you purchase, please work with our design consultants for the best match to your needs.

Why are there no ash trays or grates?
During the design and testing process, we installed grates and ash trays trying various configurations to attempt to get the boiler as easy to maintain while being as efficient as possible.  We found that the grates of all metal types break down and will require replacement frequently.  We also determined there seemed to be no savings in wood usage by having grates.  Here is a  picture of a cast iron grate used for only a few months:

Cast Iron Grate
The use of ash trays seem like a good idea until you attempt to use one.  They get clogged up, they are hard to manage and they actually make cleaning ashes a real pain.  We have determined just using our ash rake and a shovel is the easiest method to remove ash.  We normally do this weekly.  It takes about 5 minutes or less.

Why are Wood Boiler USA products better than your competitors?
Here are a few reasons:

  • Our boilers are made of thick steel
  • Our loading doors are water cooled
  • Our loading doors are the same size as the burn chamber,  allowing you load large pieces
  • Our firebox is welded inside and out; not just one side
  • Parts are easily replaced and are readily available
  • You are working with the designers and builders not a third party contact

Can I make my own underground pipe?
This comes up quite frequently with customers asking why not.  We have made our own pipe in the past.  The best items to keeping pipe from exchanging heat is stopping air flow and keeping it dry.  We have found in our testing manufactured pipe is just better, safer and performs in the long term when compared to the pipe we have made.  Soon I will post a picture of a new customer that had made there own pipe years before working with us,  they used pipe insulation, followed by a wrap of reflectix insulation.  This combo is very much like what we used to make in a 6 inch tile.  Why the pipe performed poorly it had a leak in the 6 in tile that allowed water in the pipe causing a massive amount of heat to be sent into the ground the pipes where actually covered in mud after years of water exposure, the foam insulation had retracted  causing additional heat loss when the pipe was not wet.  We did a calculation of heat lost by this customer at almost 2 cord a month during the winter months.  Needless to say they would recommend buying professional pipe.  Please note they switch to the zline pipe and had never had 24 hours burn times before.  This is a common now.  We have had customers leave the zline pex exposed all winter and say they noticed little or not heat loss and very little snow melt sitting on the ground.  These are the reason we recommend a customer purchase professional pipe it is worth it and how much did they actually save making the pipe themselves?

Here are the pictures you can actually see the mud in the pipe we dug up this section just so we could see what actually happened.  The one pictures appears like there is rocks in the pipe but that is actually mud that had dried.  Yes mud and it broke into pieces when we opened up the pipe.

Broken Pipe

Broken Pipe 2

Broken Pipe 3