Boiler Boilers can be integrated into a range of systems, from radiant slab to hot water baseboard to ventilation fans blowing across hot water coils. Efficiencies are typically measured by the Annual Fuel Utilization Efficiency (AFUE) for boilers up to 300 kBtu/h, and by thermal or combustion efficiency for larger boilers. Baseline boiler efficiencies of oil and gas (natural and propane) units are typically around 80%. With high-efficiency systems, this can rise to approximately 88% for non-condensing boilers, and as high as 95% with condensing boilers. Additional efficiency options include "low mass" (low water content) boilers, increased boiler insulation, control options to reset boiler water temperature based upon outdoor air temperatures, and variable speed control of the circulating pump operation and/or the ventilation fan operation. In all cases, NEMA PremiumTM motors improve overall system efficiencies.
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