Wood-Fired Boiler System

In the 1980's, due in large part to the Arab oil embargo, but also due to predictions of running out of oil by the early part of the 21st century, there was a large push towards energy conservation and alternative sources of energy. While building houses I became interested in house design for energy efficiency and eventually began looking at non-fossil fuel forms of home heating. I and my business partner investigated low-emission wood-fired heating systems and, in the process, sold and installed various types of heating stoves. We finally settled on a system where wood was burned rapidly and at a high temperature to more completely burn the gases. The excess heat was collected and stored in a large (3000 gallon) tank for use as needed. The system we sold was called the Dumont Boiler and, at that time, it sold for about $10,000 (before installation). Because of the cost and the size of the tank, and the falling price of energy after the oil embargo was lifted, we sold only 4 - 5 systems before we got out of the business. The Dumont Boiler is no longer made but there are other boilers built along the same lines - that is, burn hot, burn complete and store the excess heat in water.

The most efficient means of distributing the heat is through a hot-water, radiant floor system since this allows the use of water at a temperature as low as 100 degrees F . Part of the planning for our home included installing radiant floor heating during the construction phase (see Fig. 1). The radiant floor was designed to be able to heat the home at 30 degrees below zero with 100 degree water. This meant over-sizing the amount of piping required within the floor. The purpose of the low water temperature is to be able to take advantage of heat storage in water. By heating the water to 200 degrees I would have a 100 degree differential with which to work. The house was also designed to store 3000 gallons of water in a built-in tank in the utility basement (see fig. 7).

I embarked on the project finally last summer after several years of design work – both in my head and on paper. For over a year, the design of the system evolved in my head during my daily jogs. I then started putting my ideas down on paper (fig 2). I went through several iterations of the design, beginning with a top-feed combustion area but then finalizing on a front-feed combustion box. The primary reason for the front-feed was that I had insufficient ceiling height in the area where I planned to install it. (Lack of foresight when designing the home!)

The downside to a front-feed is that if the unit develops a leak, I could have a basement full of water. For that reason, the complete unit was pressure-tested prior to painting. The unit was then sanded thoroughly and painted with a rust-fixing primer. This was followed by 2 coats of epoxy primer followed by 2 coats of a super epoxy finish coat (see figs. 5 & 6).

The water storage area will be insulated with 4" of polyisocyanurate rigid insulation on all sides, then lined with an EPDM rubber lining. The only penetration in the liner will be at the front where the boiler is mounted (fig. 9).

Figure 1 - Pouring 2nd Floor Radiant Floor	Figure 2 - Boiler Blueprints	Figure 3 - Boiler Parts
Figure 4 - Welding Heat Exchanger. Note combustion chamber in back	Figure 5 - Combustion Chamber & Heat Exchanger	Figure 6 - Complete Unit
	Figure 7 - Water Storage Area	Figur 8 - Tank Area with Boiler In Place (simulated)