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.
Peerless offers two Energy Star listed, high-efficiency, sealed combustion, direct vent residential boilers that meet GreenSpec efficiency requirements. The stainless steel, gas-fired Peerless Purefire is available in six sizes ranging in input from 50 to 210 MBtuh and output from 46 to 192 MBtuh and can achieve an AFUE as high as 97%. Up to 16 Purefire boilers can be cascaded to provide a higher output. The stainless-steel, oil-fired condensing Peerless Pinnacle is available at firing rates of either 0.5 gph or 0.6 gph, with inputs of 70 and 84 MBtuh and outputs of 64 and 77 MBtuh, respectively. The Pinnacle has an AFUE of 92%. Peerless covers these boilers with a limited 12-year warranty.
Boilers heat water in hydronic heating systems, where it is distributed through baseboard radiators (convectors), panel radiators, or radiant-floor tubing. These listings include the highest-efficiency residential and small commercial gas- or oil-fired boilers and products (with less than 300,000 Btu/hour maximum output). Some water heaters—especially electronic-ignition on-demand water heaters—can also be used as boilers for heating, particularly in very-low-energy buildings.
Condensing boilers capture more energy from the combustion gases, so the flue-gas temperature is lower and water vapor condenses out as liquid and drained away. As the water condenses from the combustion gases, the heat of vaporization of the water vapor is captured, boosting the overall efficiency of the system, resulting in consistently higher efficiency ratings than other boiler types. Most experts recommend that condensing boilers not be installed with masonry chimneys because of insufficient “draw” and risk of corrosion. 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.), and whether it is capable of operation in the event of a power outage.
Energy Star lists residential boilers with an AFUE of 85% for gas or oil. Residential and small commercial boilers listed in GreenSpec are Energy Star listed with a higher annual fuel utilization efficiency (AFUE), of at least 87% for oil or 95% for gas. We may make exceptions to one of these criteria for boilers with other important features such as effective sealed-combustion or boilers that meet unique needs such as temporary construction-site heating. We also may list supplementary equipment like economizers that increase boiler efficiency.
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