With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
The LX Series of high-efficiency, gas-fired industrial steam boilers from Miura are among the lowest in the industry in terms of NOx emissions with models emitting as low as 12 ppm. Several sizes are available, ranging in output from 1,674–10,050 MBtu/hr. Thermal efficiencies for the models range from 96.6–98.8. The boilers are designed to heat tubes with a cool, wide flame which allows for low emissions as well as a compact footprint.
These listings include the highest-efficiency commercial gas- or oil-fired boilers and products (with greater than 300,000 Btu/hour maximum output). Condensing boilers capture and cool the combustion gases that are normally vented. Water condenses from those combustion byproducts, which releases additional heat and raises the overall efficiency of the system, resulting in consistently higher efficiency ratings than other boiler types.
Large commercial boiler efficiency is typically measured by “combustion efficiency” (Ec) or “thermal efficiency” (Et). Annual fuel utilization efficiency (AFUE) is not typically used for large boilers. If comparing midsized boilers with different efficiency units, note that, while not directly comparable, thermal efficiency is typically a few points higher than AFUE. Additional factors to consider are noise level, whether the system has sealed combustion with direct venting to the outdoors and/or enhanced combustion emissions controls (for NOx, particulates, etc.), whether it is capable of continued operation in the event of a power outage, and of course, ensuring that it is well matched for the application.
Commercial boilers listed here achieve thermal efficiencies of at least 96% for gas and 88% for oil.
Ratings and Commentary