A Modulating Boiler-Explained
Old style inefficient boilers have worked the same way for a hundred years: they’re either ON or OFF. Thus, when even a small amount of heat was called for, the boiler roared to life at full power, wasting precious fuel. A modulating boiler is able to vary its output, producing only the amount of heat that is required. This high tech methodology can increase boiler efficiency to as much as 98%. Typically, the old style non-modulating boilers operated in the low 80% range. Modulating boilers can be found at Blodgett Supply in either oil or gas versions.
Outdoor Reset-Explained
Outdoor reset is an option on many high tech modulating boilers to increase efficiency. The term “outdoor reset” simply means that an outdoor thermometer is tied to the boiler, constantly updating the boiler’s software on what the outside temperature is. When the outside temperature is warm, the boiler “knows” it doesn’t have to go to full power, even if there’s a sudden demand for heat or domestic hot water. On the other hand, during periods of extreme cold weather, the outdoor reset function warns the boiler to be ready for larger heating loads.
For good examples of modulating gas boilers with outdoor reset, see Blodgett Supply's Baxi boilers. For oil boilers see models available from Viessmann.