John Siegenthaler: Hydronics Workshop

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Although the market for solar thermal systems is a tiny fraction of what it once was, I still believe there are viable applications that could help in decarbonizing thermal energy systems.

Last month, we covered the basics of classifying switches and relays based on poles and throws. Once you learn these, it’s easy to apply switches and relays to create “hard-wired” control logic - part two.

The basics of relays and switches - part one.

Several years ago, I had the opportunity of visiting the Mostra Convegno Expocomfort show in Milan, Italy. It ranks right up there with the famous ISH show in Frankfurt, Germany, as a “bucket list” event for those who are passionate about hydronic heating and plumbing.

Last month, we discussed the role of buffer tanks in combination with air-to-water and water-to-water heat pumps that operate as “on/off” devices. The key concept was to turn the heat pump on and off based on changes in the buffer tank temperatures and not based on thermostats calling for heat.

More and more hydronic heating and cooling systems are being designed around air-to-water and water-to-water (geothermal) heat pumps. When the heating distribution system is extensively zoned, a buffer tank is typically installed between the heat pump and that distribution system.

Government planners, taking their queues from politicians and advocacy organizations, have steered the future of energy supply away from fossil fuels and toward renewably-sourced electricity. It’s happening on every level from the feds right down to local city councils.

Many legacy hydronic heating systems use a fossil fuel boiler to supply fin-tube baseboard heat emitters in some areas of a building and lower-temperature radiant panels in other areas. 

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. 

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.