Natural GAS Boiler, 38 MBH, 87% AFUE, Series 3

The Highly Efficient GWA-166-N-T-S3 pumps out 233,000 BTUs with an AFUE (annual fuel utilization efficiency) rating of 84.0 percent. The GWA is also equipped with flue baffles, stainless steel burners, and an automatic vent damper to maintain that efficiency. This factory-packaged boiler has many features; like a Spark-ignited (intermittent)
pilot system, cast-iron sections with built-in air separator, and an insulated heavy-gauge steel jacket.