It’s been a little more than two years since the residential boiler minimum federal efficiency standards went into effect. The standards, which were set by the Energy Independence and Security Act (EISA) in 2007 and implemented Sept. 1, 2012, required residential gas hot water boilers to meet a minimum AFUE of 82 percent; gas steam boilers, 80 percent; oil hot water boilers, 84 percent; and oil steam boilers, 82 percent.
In addition to efficiency requirements, the rule required manufacturers to equip each gas, oil, and electric hot water boiler with automatic means for adjusting the temperature for the water supplied by the boiler to ensure an incremental change in inferred heat load, producing a corresponding incremental change in the temperature of water supplied. Additionally, the automatic means had to limit the temperature of the water in the boiler to not more than 140?F when there is no inferred heat load with respect to a hot water boiler.