John Siegenthaler, P.E.

Although I’ve worked with hydronic heating for four decades and designed systems around just about every possible heat source, I would be hard-pressed to predict what might be available as hydronic heat sources 25 years from now. 

What characteristic do solar thermal collectors, hydronic heat pumps and thermal storage tanks supplied by biomass boilers have in common?

Water-to-water heat pumps, supplied from geothermal earth loops, represent a growing sector of the hydronic heat source market. Most current-generation models can produce water temperatures up to about 125° F, perhaps a little higher if you’re willing to push the compressor operating envelope.

One of the best things about hydronic heating systems is that it’s easy to integrate some method of domestic water heating. This combination has been used for decades in systems where a boiler was the sole heat source. It’s also possible when a heat pump serves as the heat source.

 All boilers that burn hydrocarbon fuels such as natural gas, propane, oil or wood produce water vapor as a byproduct of combustion.

I’ve written it before and I’ll write it again — panel radiators are one of my favorite hydronic heat emitters. I base this sentiment on several benefits. Here are a few to consider…

I’ve covered pellet-fueled boiler applications in several past issues of PME. All of them have involved hydronic distribution systems. While such applications are certainly the prevailing way pellet boilers are used, they are not the only option. It’s possible to couple a pellet boiler to a forced air distribution system.

The choice between ∆T and ∆P operation of a circulator has, at times, been the subject of rather “heated” debates. It’s almost as if a few Yankee fans are disputing superior pitching or batting performance with a few Red Sox fans. There appears to be some strong opinions involved.

As building codes and programs such as Energy Star and Passive House require higher degrees of air sealing in new construction, the use of heat recovery ventilation (HRV) is increasing.

Nearly all closed-loop hydronic heating and cooling systems are supposed to be filled with water or a mixture of water and antifreeze. The only intentional air in the system is that contained in the expansion tank.