Hydronics Holds It All Together

How hydronics is essential to the future of solar and geothermal thermally based systems.

I’ve always been fascinated by how some highly skilled hydronic heating pros can assemble thousands of individual components into smooth-operating, custom-designed systems. From microprocessor-controlled heat sources, to specialized circulators, to a knowledge of flooring material for radiant heating applications, modern hydronic pros need a wide spectrum of expertise to pull this all together.

Still, the hydronics share of the U.S. heating market hasn’t changed much over the last two decades. Sure, there are locations where market percentages are relatively high — the ski areas in Colorado come to mind. Still, the vast majority of those building homes in this country over the last two decades did not decide to install hydronic heating.

We could spend hours debating the underlying causes of this reality. However, instead of “crying over spilt milk,” why not look forward? As I see it, the possibility for one of the broadest expansions of the North American hydronics market is at our doorstep.

Big words, you say. After all, it’s easy for writers to spread continued optimism. They aren’t out there in the trenches facing tight credit, increasing material prices, and a constantly expanding cyber marketplace where hardware is sold to anyone with a credit card and an Internet connection.

So why the optimism? Well, let’s start with a few key words.

If you’re like me, you probably have a stack of trade magazines piled up in your office for eventual reading. Go look at the stories listed on the covers of those magazines over the last two years. Chances are you’ll see words such as green, sustainable, renewable, conservation, solar, geothermal and, of course, efficiency.

Now comes the question: What HVAC technology unifies all these words and the concepts they represent? (Hint: It starts with the same letter as H2O.)

Hydronics technology is the glue that holds almost all thermally based renewable energy systems together.

Beyond The Heat Source

Take a look at a solar thermal system for domestic water heating, or a combisystem that supplies both space heating and domestic hot water. What hardware do you see? Circulator(s), tubing, venting, valves, air separators, expansion tanks and so forth. This is all hydronic hardware. The “new” components would be the collectors and perhaps a storage tank that’s slightly different from a standard indirect water heater.

Next, go look at the hardware in a geothermal heat pump system. Flexible tubing buried in the ground, rigid tubing, circulators, valves, expansion tanks, etc. Sure, the heat pump is a new heat source, and fusion welding of polyethylene pipe is a new skill that will probably take most technicians about an hour to master, but in the end, the success or failure of a geothermal heat pump system depends on installing the hydronics correctly.

The same could be said about solid fuel boilers, micro-combined heat and power units and small-scale gas-fired absorption chillers. The heart of these contemporary systems is the heat-producing equipment, but their “backbone” is the proper application of hydronics technology.

It Wasn’t Covered

Imagine an enthusiastic and technically competent young person who wants to be part of the next generation of renewable energy professionals. He attends one of many intensive training programs on installing solar thermal systems. While there, he learns about solar pathfinders, the proper placement of solar collectors, how to properly fasten those collectors to a roof, how to connect the collectors to the storage tank and how the controller that runs the solar array circulator operates.

After a few months of successfully installing what are now mostly “plug-and-play” solar DHW systems, along comes an opportunity to design and install a solar combisystem, one that links a larger storage tank and a boiler to a floor heating system.

Somewhere along the way this solar energy specialist heard that radiant floor heating systems operate at low water temperatures, and thus are well-matched to solar heat input. Since there wasn’t time to cover the specifics of radiant floor heating, the Internet-savvy technician goes online to one of many sites where the parts and pieces of radiant panel heating systems are sold.

He reads some do-it-yourself instructions and purchases the components needed to staple 1/2-inch PEX tubing directly to the bottom of the subfloor and cover it up with a layer of bubble foil insulation. This is the infamous “plateless staple-up” approach that has tested the reputation and the liability coverage of its share of installers. But remember, the solar specialist isn’t aware of such issues. He installs the materials just as the online instructions indicated.

Fast forward to some cold but sunny days the next winter. The “auxiliary” boiler in the combisystem runs most of the time, even when the sun is out. The storage tank only gets lukewarm, and the fuel savings anticipated by having the solar collectors just aren’t appearing.

Some of you probably know what’s happening. To release heat at the rate the building needs it on a cold day, the water in a plateless staple-up radiant floor panel may require water temperatures of 160 to 170 degrees F. Although it’s possible for some collectors to reach these temperatures on sunny winter days, the amount of heat they can transfer to the system under such conditions is very limited. In short, the plateless staple-up floor heating was a terrible match for the operating characteristics of the solar collectors.

So why would a technically competent solar technician end up in this situation?

Because he didn’t have a broad knowledge of hydronic heat emitters and distribution systems. Remember, this is the “glue.”

Although some of us may think subjects such as radiant panel heating are now well-understood by our industry, there is a whole generation of eager renewable energy enthusiasts out there to whom such information is brand new.

I’ve seen this firsthand when giving seminars on modern hydronics to groups of individuals specializing in renewable energy and building science. Although these seminars show and describe how the solar subsystems operate, the majority of questions deal with the specifics of radiant heating, smart circulators, distribution system design and other hydronic essentials.

These subjects are typically not taught, at least not in detail, at most solar technology workshops today. These issues will make or break the performance of any solar combisystem. Ultimately they also will play a part in determining if the currently strong interest in renewable energy heat sources is truly “sustainable.”

The ability to unify renewable heat generation with highly efficient heat distribution and superior uncompromising comfort is a unique benefit of hydronics. It’s also why I believe the hydronics industry is poised for strong future growth. However, our industry needs to continually communicate this message to the masses.

 

John Siegenthaler

John Siegenthaler, P.E., is a mechanical engineer graduate of Rensselaer Polytechnic Institute, a licensed professional engineer, and Professor Emeritus of Engineering Technology ad Mohawk valley Community College.

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