Steam and hot-water heating joined hands a long time ago to make up what we today call “hydronics.” Both systems run on water, and they’ve been around for hundreds of years. The Institute of Boiler and Radiation Manufacturers coined the term hydronics in 1946 to make the science of heating a building with water sound sexy — like “electronics.” That word — electronics — has been with us since 1900 and was all the rage in the booming years just after WWII.
Most hydronic systems are probably older than your parents and have seen changes throughout the years. The result of some of these changes has been painful because now everyone gets to work on hydronics; system knowledge is not a prerequisite. A lot of this stuff got made up as they went along. Where to place the circulator when it finally showed up? How to size a radiator? How to rate that radiator?