The Problem

Most hot-water radiator systems were installed a half-century ago and are still in use today. They offer a combination of comfort, quiet, and efficiency that can’t be matched by modern forced-air systems. However, many of these systems (even those retrofitted with modern boilers) suffer from one big problem: uneven heating of the radiators. Some radiators are too hot, while others never seem to warm up enough.

Not only does this problem affect the heating comfort of your home, but attempts to compensate for the uneven heat often result in significant decreases in heating efficiency.

Every boiler has a pump (or "circulator") which moves the heated water out of the boiler and throughout the house. Traditionally, the circulator is controlled by a temperature switch or thermostat relay. These types of controls prevent the boiler from overheating, but can't achieve even heating. Even in well-plumbed systems, temperature differences remain between radiators. Small radiator temperature differences cause much larger effects on comfort: a radiator at 35°C puts out less than half of the heat of an identical radiator at 40°C.

What about adjusting the valves? Standard radiator valves cannot be used to solve the problem of unevenly heated radiators. Due to the different pipe lengths leading to each radiator, the valves would have to be re-adjusted with every outdoor temperature change. That's why no amount of adjustment ever seems to be "just right."

Yesterday's Solution: Many heating professionals, realizing that the standard circulator control is the source of the uneven heat, simply bypass it and leave the circulator running continuously. This does achieve even heating, but it has significant drawbacks: constant pump noise, increased circulator wear, and surprisingly high electricity usage: a standard 2-amp circulator running continuously uses over 2000 kWh per year of electricity, as much as FOUR full-size refrigerators!

Today's solution: The Smoother operates the circulator pump at the exact times needed, eliminating temperature variations between radiators regardless of radiator location or outdoor temperature changes – and saves 75% of the electricity used by continuous circulation!

Want more details on the science of hot water heating? Read our Technical Paper: Even Heating of Hot Water Radiators. This is a .PDF file. Click here to download the Adobe Acrobat .PDF reader.