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  • Baltu Yorkos, PE, LEED AP

Boiler Replacement Advantages

Boiler efficiency is measured by annual fuel efficiency (AFUE), for units under 300,000 BTU input. Federal Trade Commission requires new boilers to display their AFUE so consumers can compare heating efficiencies of various models. AFUE is calculated efficiency which attempts to estimate how well the appliance converts the energy in its fuel to heat over the course of a typical year.


Specifically, AFUE is the ratio of annual heat output of the boiler compared to the total annual fossil fuel energy consumed by boiler. In general, an AFUE of 90% means that 90% of the energy in the fuel becomes heat of the building and other 10% escapes up the chimney and elsewhere.


An ell-electric boiler has no flue loss through a chimney. The AFUE rating for an all electric boiler is between 95% and 100%. However, despite their high efficiency, the higher cost of electricity in most parts of the country makes all electric boilers and uneconomic choice.


The minimum AFUE rating requirements for boilers varies based on the type of fuel and the heating medium used. All boilers manufactures have the following minimum AFUE ratings: 82% for a gas fire hot water boiler and 82% for an oil fired steam boiler. In addition, gas fired boilers are not permitted to have constant burning pilot and hot water boilers are required to have and automatic means of adjusting the water temperature to match the inferred heat load.


Besides the type of fuel and heat medium used, boilers models are primarily designed to either operate in a non-condensing or condensing mode. Non-condensing boilers have efficiency rating of approximately 80 to 88% and condensing boilers have efficiency above 88%. A condensing boiler condenses the water vapor produced in combustion process and uses the latent heat from this condensation. The AFUE rating for condensing boiler can be much higher (by more than 6-8%) than a non-condensing boiler. it is important to note that there are significant differences between these non-condensing and condensing product groups, and even larger differences between new installations and replacement installations for these various products. To achieve the full efficiency benefit, they must be used in the correct applications.


Today's new cast iron boilers are much more efficient than those existing in the field 20+ years old, so an upgrade can potentially provide significant savings when replacing a cast iron boiler with new cast iron boiler when used in the correct application.


Retrofiring Boiler system

in certain instances, owner might not be financially willing or able to replace the boiler. Boilers can sometimes be retrofitted to increase their efficiency. These upgrades improve the efficiency of otherwise sound, older systems. But the cost of retrofits shall be carefully weighted against cost of a new boiler, especially if replacement is likely within a few years. retrofits are fuel specific, but general, some retrofitting options that can improve a system's energy efficiency including programmable thermostats, adding zone control for hot water systems and installing outdoor reset controls. Water treatment products can also be used to improve system circulation, heat transfer and help prevent scale build up.


Replacing Boiler

Although older boilers has efficiencies in the range of 56% to 70%, modern boilers can achieve efficiencies as high as the mid-nineties, converting nearly all the fuel to useful heat for the building. Energy efficiency upgrades and new high-efficiency heating system can often cut fuel bills and emission output in half. Upgrading the boiler from 56% to 90% efficiency in an average cold-climate building could potentially save 1.5 tons of carbon dioxide emissions each year if heated with gas, or 2.5 ton if heated with oil. if the boiler is old, worn out, inefficient, or significantly over sized, the simplest solution is often to replace it with a modern model. Old coal burners that were converted over to oil or gas are prime candidates for replacement, as well as gas boilers with pilot lights rather than electronic ignitions. Regardless if its is a planned or unplanned boiler replacement, a properly sized boiler will operate the most efficiently when properly matched to the application.


In general, an estimate of annual savings from heating system replacements can be made by using the table below, which assumes that both heating systems have the same heat output and the boiler properly matched to the application.





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