The XC21 air conditioner has an efficiency rating of up to 20.5 SEER and uses R-410A. It has a high-efficiency outdoor coil that provides exceptional heat transfer and low air resistance for more efficient operation, says the company. It is an Energy Star product. It has a sound level as low as 69 dB. Engineered with SilentComfort™ technology, the XC21 includes innovations to reduce noise, including a patent-pending fan design, compressor with vibration insulators, a sound-dampening fan grille, and a Hushtone® cabinet. It also features the company’s System Operations Monitor, which reviews system performance - similar to diagnostics systems in cars. The compressor has a limited warranty for 10 years in residential installations, and five years in nonresidential installations.

Lennox Industries Inc., Dallas, 800-953-6669;

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