Prairie Home Furniture

Celebrating  The  Arts & Crafts  in  Bozeman,  Montana

The Boiler
Above is the original coal burning boiler converted to natural gas.  The white coating covering the boiler is asbestos.  Sounds extremely hazardous, but as long as you don't break through its protective covering (paint, probably lead based) it's safe.  The asbestos is insulating the boiler's outer casing, allowing the water within its walls to heat quickly, like a cover on a heating pot. Whenever the asbestos was added, it marked the beginning of efficiency awareness for the boiler. Another addition to the system's efficiency, dated by the magazines used, was wrapping all the exposed feed/return pipes in the basement with 1940's Saturday Evening Posts' magazines. This wrapping keeps the heat from escaping, allowing the water to remain hotter longer as it travels throughout its cycle.  I was impressed by the variety of Norman Rockwell covers, as well as, reading the many fun "outdated" articles.  I will be replacing the magazines with a more efficient wrapping, in addition to, giving the asbestos another protective coat of acrylic paint. Yes, at this time, I do plan preserving this old relic, even though it wasn't love at first sight, but after becoming familiar with its design and function, I became convinced I could bring this boiler back to its original intent, and in the process produce an efficiency of 80 plus percent compared to the mere 55% as it operates currently.  Let's now study how this heating system was designed, and by doing so, I hope to demonstrate my sound reasoning for preserving it.  

Although this boiler is the "heart" of the home's heating system, it lacks a circulation pump. No mechanical pump is necessary to move the hot water through specifically designed/sized pipes to radiators throughout the many rooms of this two story Bungalow.  So how does heated water get from below ground level to the second story and everywhere in between?  This is the fascinating aspect of this heating system. This system relies on convection to circulate hot water through its heating cycle. Convection is the transfer of heat by the circulation of heated liquid or gas, in this heating system, water is used as the heat carrier.  In other words, heated water becomes less dense and begins to rise, as it rises the water will "push" the cooler, more dense, water at the top of the cycle down until it once again reaches the boiler where it's reheated, thus re-initiating the heat/convection cycle.  Most people refer to this heating system as a "gravity fed" hot water system. 

As with all hot water heating systems, there must be an expansion tank to allow room when heated water expands.  This expansion tank is located at the highest point, usually in the attic, and has an open overflow vent draining onto the roof.  My system is unique because it's a closed system, meaning there's no vent; having no vent allows the heating system not to take in oxygen from the outside, causing corrosive damage to internal pipe and fittings.  After 100 years, there's no corrosive damage within my heating system.

"Just add hot water," is all this system needs for the physics of convection to begin the process of warming the house.  To have created this heating system to function as well as it does took a lot of technical expertise in designing and installing, so for me to dismantle and discard it would be a total waste of a reliable/earth friendly technology not to mention the cost to replace a compatible system.  It's not the concept behind the convection/gravity fed system which led to this system's apparent demise, but rather its inefficiency of producing the hot water necessary for the system to perform.  The way I came to view this system is if one were to find an efficient way of heating water and deliver this hot water to the feed lines directly above the existing boiler, you could create a reliable/ earth friendly heating system which could last another 100 years. 

Opening the broiler's front door while it's operating, you'll discover this boiler, in its current state, is extremely inefficient.  You'd  swear there was a medieval dragon exhaling 18" flames up a 14" diameter flue. Although there's a baffling system within the boiler, the flue's temperature is way too high, indicating a lot of heat is not heating the circulating water as it could/should, but rather escaping/"convecting" up the chimney, lost/wasted forever.  The only noise this heating system produces is the streaming of a greenhouse gas, noisily through the 2" pipe while feeding its insatiable dragon.  My goal is to tame the dragon. 
The question is how to heat the system's water supply as efficiently as possible.  With Butte's 300 plus sunny days/year, a passive solar system could be designed to feed the boiler, an array of solar panels could generate electricity to power heating elements within the main feed lines, geo-thermal (not in Butte) is another possibility.  While brainstorming, I decided there are multiple ways to heat the system's water, why not incorporate more than one energy source.  That's when I decided to reconvert the boiler back to burning wood/coal, preferably wood (renewable resource). There's one energy source, not necessarily the primary.  For the second energy source, I decided to install a high efficiency natural gas condensing combination boiler, with an efficiency of 92.5%.  This condensing boiler will also supply domestic hot water where needed.