Siggy is in a league of his own when it comes to engineering. In addition his course material for educational institutes and industry organizations are the benchmark for learning about application and design as are his magazine articles. Specialties include solar energy applications, super-insulated construction, and hydronic heating. Today the company focuses solely on state-of-the-art application of hydronic heating. Through extensive research and application of engineering principles, Appropriate Designs has developed advanced modeling methods for simulating the thermal and hydraulic performance of hydronic systems. These models have been used to develop software-based sizing and selection programs for several manufacturers, as well as numerous publications, and training seminars.
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Tweet March 21, by John Siegenthaler As the North American hydronics industry has grown, so has the complexity of its systems. Many installations that are now featured as award winning examples of hydronic heating contain thousands of parts and pieces. They can be so complex that only the person who designed and installed them understands how they operate, or can fix them when they do not. That is not good for the system owner or for the industry.
Although there are some buildings, perhaps even some single family homes that benefit from having a dozen or more heating zones, as well as a wide mixture of heat emitters, they do not represent the mass market in which hydronics still only holds a single-digit share.
Promoting the concept of hydronic heating with photos of elaborate systems containing lots of hardware can easily send the wrong marketing message. It is simple in that only one type of heat emitter is used; simple because the control logic is pre-engineered rather than customized; and simple from a piping layout standpoint.
Perhaps you are thinking that simple excludes being state of the art. This is not the case. The system discussed here uses cutting edge concepts such as outdoor reset control, boiler modulation and variable speed pumping.
It personifies the state of the art in hydronics technology but with far fewer parts and pieces. A piping schematic of the system is shown in Figure 1.
Figure 1 Piping schematic for simple system We will examine each subsystem independently and then look at how they all work together. A wide assortment of such boilers is available in North America, and most are capable of operating with either natural gas or propane. All have internal control logic that allows them to regulate the water temperature supplied to the heat emitters in response to outdoor temperature e.
The warmer it is outside the lower the boiler temperature and the higher its efficiency. The system must be stable and efficient during these times, as well as under brief peak load conditions.
During this mode of operation circulator P2 is turned off while circulator P1 operates. Each radiator represents a separate zone. There will often be times when the heating load perhaps a single room is far lower than the minimum heat output rate of the boiler.
Under such circumstances any low mass boiler with minimal water content will short cycle. This can lead to premature failure of ignition and combustion components. Short cycling is avoided by installing a well-insulated buffer tank in the system to provide additional thermal mass between heat production and heat release. The boiler maintains the temperature of the buffer tank based on outdoor reset control. A gallon buffer tank would provide 44 per cent more thermal mass than a pound cast-iron boiler with a gallon water volume.
The buffer tank also hydraulically separates the pressure dynamics of the boiler circulator P2 from those of the variable speed distribution circulator P3. It provides a low flow velocity zone allowing air bubbles to rise to where they can be captured and expelled through an automatic float-type vent. These panels offer several benefits: They are adaptable to different interiors. They come in a variety of heights, widths, and depths that allow them to fit into a wide variety of situations.
They are one of the easiest heat emitters to install in new homes as well as retrofit applications. They are relatively light and can be supported by almost any wall. Figure 2 Non electric thermostatic radiator valves They lend themselves to room-by-room zoning using non-electric thermostatic radiator valves, as shown in Figure 2, providing fully modulating room-by-room comfort control without a mile of thermostat wires.
This is a tremendous benefit relative to the complexities and installation time associated with wire-based thermostats in every room. Panel radiators have very low thermal mass and thus respond quickly to changing internal heat gain situations. In short, they warm up and cool down much faster than heated floors. This is especially desirable in buildings with significant internal heat gain potential. I suggest sizing panel radiators for design load output with a supply water temperature of F.
Operating panels at relatively low water temperatures also increases the ratio of radiant to convective heat output, which further enhances comfort.
Each panel radiator is equipped with a dual isolating valve enabling it to be totally isolated from the remainder of the system if it ever has to be removed. Because the panel radiators each have their own balancing valve, as well as dual isolating valves at the supply and return connections, it is not necessary to use a manifold station equipped with such valves.
A simple copper manifold such as the one shown in Figure 3 is fine. Figure 3 Valveless copper manifold The homerun distribution system provides several advan- tages: The small diameter flexible tubing can be routed through the framing cavities of the building much like electrical cable. Homerun systems deliver the same water temperature to each heat emitter. This simplifies sizing since the temperature drop associated with series type circuits is not present.
It also allows each heat emitter to take equal advantage of outdoor reset control. In combination with thermostatic valves at each panel radiator, homerun systems allow the temperature of each room to be individually controlled. The master bedroom can be kept cool for sleeping while the master bathroom remains toasty warm for a morning shower. Unoccupied rooms can be set at lower temperatures to conserve fuel.
These are now widely available in North America. Two examples are shown in Figure 4. Figure 4 Variable speed pressure regulated circulators In this type of system the circulator should be set to maintain a constant differential pressure. This keeps the flow through the active zone circuit stable regardless of what other zones happen to be on, off or at some intermediate flow rate.
It is just the right amount of pumping effort under all conditions. These circulators also operate on a fraction of the electrical energy required by a typical fixed speed circulator with a permanent split capacitor motor.
Imagine an entire heating distribution system, in a typical North American house, operating on less than 45 watts of pumping power on the coldest day of the year. It is possible with this technology. It is one of the easiest distribution systems to install in new and retrofit situations. Wiring consists of supplying power to the boiler and three circulators.
No room thermostats, transformers, or zone relay panels are required. Domestic water heating is handled as a prioritized load allowing for the fastest possible recovery of tank temperature. If you feel the systems you are presently installing are getting a bit complex, consider giving this concept a try. It will quickly convince you that hydronic systems do not have to be complex to be state of the art.
John Siegenthaler, P. He has over 34 years experience in designing modern hydronic heating systems.
ISBN 13: 9780766816374
Tweet October 28, by John Siegenthaler Figure 1 The pressure drop within the copper basketball header would be very low, but not quite zero. If this header were well insulated it could also provide very low but not zero heat loss. We live in a world where, for the most part, theoretical ideals can only be approached rather than fully realized. For example, imagine a building with heat loss characteristics such that the rate of heat loss always matched the rate of internal heat generation from sunlight, people, and equipment.
Specialists In The Use of Hydronic Comfort Heating
Modern Hydronic Heating Residential by Siegenthaler