The Benefits of High-Efficiency Boilers    

With the increase in natural gas prices, and the encouragement to be "environmentally friendly", many facilities have begun replacing their existing conventional boilers with new high-efficiency condensing boilers.  The U.S. Department of Energy states,

"Non-condensing-type hydronic boilers and water heaters are unable to recover the latent heat of water in the combustion products of fuels that contain hydrogen and are, therefore, subject to the theoretical limit of the fuel lower heating value resulting in published full-firing rate efficiencies of 78—85%. In addition, cycling losses of 10—50% may be incurred by non-modulating (on/off) units operating at less than full load. A modulating/ condensing fuel-fired water heater or hydronic boiler can be an energy efficient alternative to such conventional units" (Technology for increasing water heater/hydronic boiler efficiency, June, 1998).  

The dividing line between these efficiency ranges is based on the boilers ability to withstand the condensing of flue gases. 

Water vapor which is found within the boiler's combustion gases contains a large amount of energy.  In conventional boilers this water vapor is released directly into the atmosphere through the flue, however high-efficiency boilers are able to capture this previously lost energy.  By returning water to the boiler at less than 135 degrees F, these water vapors can be exposed to a cool heat exchanger surface.  At this point water vapor naturally falls below its dew point, forcing it into a liquid state.  This change is state causes a process known as condensing to take place which releases approximately 1,000 BTUs of heat for every pound of liquid created.  When condensing occurs, a mildly acidic condensate resulting from the impurities in the fuel (mostly sulfur and nitrogen) remains on the surface of the heat exchanger. This is an important feature to be aware of when selecting a boiler because unless the unit has been constructed from the highest-quality materials, and is designed to drain freely, over time this fluid will destroy the integrity of the heat exchanger and the lifespan of the boiler.  This condensing process can increase the efficiency of a boiler or water heater by as much as 12%, turning more of the boiler or water heater's fuel into usable heat.  A 20% fuel savings is typical when converting to a condensing style boiler, however by using the highest efficiency boilers available a savings of upwards of 50% in overall gas consumption has been seen at some installations in Minnesota.

Although there can be more up-front cost when installing high-efficiency boilers in comparison to conventional boilers, the dramatic energy saving seen over the life of the boiler typically out weighs this cost differential.  The decision however, is simple for someone who understands that all energy lost is waste, and that means lost revenue.

For more information on increasing fuel savings beyond the typically seen 20%, and how to minimize the up-front cost of a high efficiency boiler visit http://www.aerco.com/ or call R.M. Cotton Company.