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Hydronic Heating and the Independent Home: The SETH System™ Radiant heating systems that use hot water to deliver heat are growing quickly in popularity. Whether using baseboard fin-tube radiators or imbedded tubing in the floors, hydronic (hot water) radiant heat is one of the most comfortable and unobtrusive ways to heat a home. It can deliver heat silently and evenly while allowing an exceptional degree of control. Also growing in popularity are homes that generate all or part of their own electric power from renewable sources. Whether from photovoltaic (solar electric) modules, wind, or hydroelectric power, living "off-grid" has become a viable option for tens of thousands of homeowners. By designing for maximum efficiency and eliminating wasted energy, most off-grid homeowners live comfortably using a small fraction of the electricity of a conventional home. Manufacturers of radiant boilers and heating systems have given scant attention to the electrical demands of their equipment. For a home that is served by conventional utility power, the relatively low electrical demand of a conventional hydronic heating system is acceptable. In an off-grid home, however, or a home with both renewable and utility power, a conventional hydronic installation will often lead to disappointing results. When a standard boiler system is installed in an independently powered home, the electrical demand of the heating system alone can exceed the daily output of the renewable power system. The owners have often discovered that the pumps and boiler controls demanded all of the available solar or wind power every day during winter. The SETH System™ Solutions The Positive Energy SETH Systems were developed specifically to solve this problem by greatly reducing the electrical demand of a hydronic heating system. Both systems typically reduce electrical demand by 50-90% or more over conventional installations. This reduced load means substantial cost savings for the entire renewable power system. In new construction of an independently-powered home, a SETH System easily pays for itself in power system savings alone! The systems are intentionally designed to reduce or eliminate the constant and excessive electrical load inherent in the transformers, pumps, controls, and other equipment common to conventional hydronic boiler systems. A plumbing or HVAC contractor with standard tools can install each model. Neither system requires any internal modifications to existing equipment, so all factory warranties are preserved. The SETH System Stout is used with a conventional hydronic boiler of any size. The SETH System Light, developed for smaller homes, is teamed with a tank water heater, that may incorporate an internal heat exchanger for solar thermal input. Each is a complete, simple, and reliable package of hydronic control and distribution equipment. How the SETH System Works The inverter is the component in an independent electric power system that turns stored low-voltage battery power into high-voltage power that is like conventional utility power. An AC boiler contains transformers and control circuitry that are constantly drawing power through the system inverter. Although the amount of power these transformers require is relatively small, the inverter must always be "awake" in order to provide that power. This amounts to what is called a phantom (or ghost) load - the inverter's wakeful state is also a continuous draw on the system's batteries. The SETH System Stout achieves its remarkable results via a series of relays and thermostats that control efficient DC circulation pumps. Power flows to the pumps when the thermostats call for heat; no power is consumed when the call for heat is satisfied. The SETH System Stout unit also, through a proprietary control circuit, effectively regulates the system inverter power to an AC boiler, allowing the inverter to operate only when heat is required. This prevents the boiler (and therefore the inverter) from always being on, and translates to a significant reduction in the amount of energy consumed by the hydronic heating system. Each SETH System Stout and Light can control up to six zones. A "Link" terminal allows any number of Light units to also function as an add-on slave unit to a master Stout unit. There is no limit to the number of zones that can be controlled by the unit. Certain zones such as a kitchen or living space will almost always want to be heated, while a guest bedroom only requires heat when there are guests. All zone control rests with the plumber planning the installation, comparable to a conventional installation. The SETH System Stout and Light controls can handle a variety of specialized control tasks. For example, a sidearm domestic water tank can receive priority status, such that a call for domestic hot water always turns off floor radiant zones until satisfied. Priority switching can allow solar panels to provide all or most heat, with a burner firing only if needed. It can also combine several different means of heating into one system; for example, solar hot water collectors may be combined with a propane flash heater or an AC boiler, with heat being drawn from each source as it is available. In addition to standard Stout and Light systems, we can provide custom design and installation services incorporating a variety of specialized applications, multiple heat sources, multi-stage controls, and other custom work. Bristol Stickney, a solar consultant with over twenty years' experience with solar thermal and hydronic design, will provide most custom design work. Mr. Stickney also provides building thermal performance computer modeling using Energy-10 software developed at the National Renewable Energy Laboratory. He may be contacted through Positive Energy. Our simplest system to date has been a single-zone in-floor radiant system using a tank-type water heater. Our most complex system to date, as shown on the right, was installed at a ranch near Rowe, New Mexico. It includes: -- sixteen infloor radiant zones; --two indirect-fired domestic hot water tanks; --a hot tub; --a snow-melt zone; --a lap pool (controlled as a dump zone for excess solar heat); --a two-stage, 325,000-BTU LP boiler, with two Taco primary circulation AC pumps; --eighteen Heliodyne 4X10 solar thermal collectors; --two PV-direct Dankoff SunCentric solar thermal circulators; --two Six Rivers 640-gallon thermal storage tanks with three heat exchangers each; --six Goldline electronic remote-sensor thermostats of various models; --all powered by 48-volt DC battery power. The current retail cost of the standard SETH System Stout control unit is $1075, and the standard SETH System Light control unit is $650. Custom units are priced on an individual basis. In addition to the SETH System control unit, one zone pack is required for each heating zone or equivalent function. The retail cost of each zone pack is $380-$475, depending on the circulation pump included. Dealer inquiries are invited. Presently, each SETH control unit is hand-built and tested in the Positive Energy shop. As part of our ongoing product improvement process, we have worked with Sandia National Laboratory to develop a prototype production model using a printed circuit structure. History The SETH System concept has been in development for over ten years. In 1998, Positive Energy, Inc. developed a production prototype with contract assistance from the Technology Commercialization Office of Los Alamos National Laboratory. In 1999, a second grant provided funding for patent protection and prototype manuals. More than two dozen custom and prototype SETH System Stout and Light control systems have been successfully operating in northern New Mexico and southern Colorado, providing real-world experience. In May, 2001, the U.S. Patent Office issued Utility Patent No.6,237,855, protecting the fundamental design of the SETH System.

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