GREEN SYSTEMS | SOLAR SOLUTIONS | CONTINUED FROM PAGE 63
The focus is on pressurized glycol/ hydronic systems since these systems can be applied in a wide variety of building geometries and orientations with few limitations.
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from solar heat gain but also from the installation of high efficiency combustion and the addition of heat saving control strategies, which can be monitored and adjusted as needed. Solar priority over the boiler is provided both by the piping configuration and by the control logic. Solar direct heat for the floors has a priority over heat storage in the water tank. Heat storage is provided by the mass floors and controlled by the SLIC controller, using virtual two-stage room thermostats under central software control. Heat storage is also optimized in the DHW water tank and recirculator by software control. The SLIC controller is programmed to save heating fuel in every way possible such as stranded heat recovery and intelligent priority control, based on temperatures and critical loads.
Electrical saving strategies The opportunities for electrical savings in a heating
system, although sometimes small, are always worth considering. Here are some of the steps taken on this job. The boiler circulator is disabled when solar-only temperature is available. Multi-speed circulators are used and set to the lowest speed that is effective for each job. The minimum number of transformers is installed to eliminate the “phantom load” that transformers consume.
“Latching” zone valves are used that require no power when fully open or closed. There is no primary pump; all circulation through the
flow center is provided by the secondary pumps that supply flow from the heat sources to the heat loads. Solar circulation for collectors using closed glycol loops can be achieved with very small pumps and/or solar electric PV pumps.
Overheat control and cooling schemes The SLIC controller is programmed to prevent solar
overheating and to maintain safe high limits and comfort temperatures in a variety of ways. The DHW tank is used as a heat accumulator by day and can be cooled through the solar panels by night, if needed. The solar glycol high limit temperature can be controlled with cool fluid from the garage floor (or other floor zones) when needed. The floors in the warmest rooms in summer can be cooled by night circulation through the solar panels.
Report from the owner
The heating fuel
consumption for this house has been carefully recorded by the owner, before and after the solar heating retrofit and dating back ten
e Turn to SOLAR SOLUTIONS on p 68
I e Circle 38 on reader reply card
n this series of articles, I have been making the case that the key ingredients for solar/hydronic design and installation can be divided into six categories, listed below, roughly in order of their importance. 1. RELIABILITY 2. EFFECTIVENESS 3. COMPATIBILITY 4. ELEGANCE 5. SERVICEABILITY 6. EFFICIENCY The success of any solar hydronic home heating installation depends on the often-conflicting balance between any of these six principles. Finding the balance between them defines the art of solar heating design.;
phc march 2011
www.phcnews.com
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