Idronics#6 Feat_rev2.indd 1 5/4/10 2:57:56 PM CaleffiCaleffi North North America, America, Inc. Inc. 98503883 South W. Milwaukee 54th Street Rd Franklin,Milwaukee, WI 53132 Wisconsin 53208 T:T: 414.421.1000414.238.2360 F: F: 414.421.2878 414.238.2366 Dear Hydronic Professional, Dear Hydronic Professional, Welcome to the 6th edition of idronics, Caleffi ’s semi-annual design journal Welcomefor hydronic to theprofessionals. 2nd edition of idronics – Caleffi’s semi-annual design journal for hydronic professionals. The global recession has slowed nearly all industries over the past year. TheHowever, 1st edition despite of idronicsdeclines was in construction, released in January solar water 2007 heater and distributed shipments to over 80,000in the US people increased in North 50% America. during 2008.It focused on the topic hydraulic separation. From the feedback received, it’s evident we attained our goal of explaining the benefits andAs more proper and application more HVAC of professionalsthis modern design become technique familiar forwith hydronic solar water systems. heating, many recognize opportunities to extend solar thermal technology A Technical Journal Iffor you combined haven’t domesticyet received hot a water copy andof idronics space heating#1, you applications.can do so by Thissending is a in the attachedtrend our reader parent response Caleffi SpA card, identifi or by ed registering several years online ago at in www.caleffi.us Europe, and is. The from publicationnow a topic willof growing be mailed interest to you here free inof North charge. America. You can For also this download reason, the Caleffi Hydronic Solutions completesolar “combisystems” journal as a PDF was fileselected from our as theWeb topic site. for this edition of idronics. ThisCaleffi second is pleased edition to addressesprovide the air information and dirt in in hydronic this edition systems. to assist Though those not a new topicdesigning to our solar industry, combisystems. the use of modernWe also high-efficiencystand ready with equipment state-of-the-art demands a thoroughhardware understandingto support installation of the harmful of such effects systems. of air and dirt, as well as knowledge on how to eliminate them. Doing so helps ensure the systems you design will CALEFFI NORTH AMERICA, INC operateWe encourage at peak you efficiency to send and us feedbackprovide long on thistrouble-free edition of service. idronics by 3883 W. Milwaukee Rd e-mailing us at idronics@caleffi .com. Milwaukee, Wisconsin 53208 USA We trust you will find this issue of idronics a useful educational tool and a handy referenceFinally, if you for yourare interested future hydronic in previous system editions designs. of idronics, We also pleaseencourage go to you to send uswww.caleffi feedback .us on wherethis issue they of can idronics be freely using downloaded. the attached You reader can alsoresponse register card or by Tel: 414-238-2360 e-mailingto receive us future at [email protected] issues online. FAX: 414-238-2366 Sincerely, E-mail: idronics@caleffi .com Website: www.caleffi .us Mark Olson General Manager, To receive future idronics issues Caleffi North America, Inc. FREE, register online www.caleffi .us 23 DRAINBACK SOLAR COMBISYSTEMS INDEX Advantages of Drainback Systems Disadvantages of Drainback Systems 3 INTRODUCTION Open-Loop vs. Closed-Loop Drainback Systems Operation of a Drainback System 3 FUNDAMENTALS OF SOLAR COMBISYSTEM DESIGN Siphon Limitations Essential Design Principles Sight Glasses Instantaneous Collector Effi ciency Tank Piping Connections Freeze Protection Drainback Combisystem #1 Drainback Combisystem #2 6 SPACE HEATING OPTIONS Drainback Combisystem #3 Heated Floor Slabs Drainback Combisystem #4 Heated Thin-Slabs Other Site-Built Radiant Panels 40 PERFORMANCE EXPECTATIONS Panel Radiators Estimations Forced-Air Distribution Systems f-chart Analysis Case Studies 13 ANTIFREEZE-BASED SOLAR COMBISYSTEMS Collector Orientation in Combisystems Advantages of Antifreeze-Based Systems Storage Tank Size in Combisystems Disadvantage of Antifreeze-Based Systems Heat Dump Provisions 44 SUMMARY Antifreeze-Based Combisystem Designs Antifreeze-Based Combisystem #1 45 APPENDIX A: Piping Symbol Legend Antifreeze-Based Combisystem #2 46 APPENDIX B: Heat Exchanger Performance Antifreeze-Based Combisystem #3 48 APPENDIX C: Tank and Piping Volume Formulas Antifreeze-Based Combisystem #4 49 APPENDIX D: Unit Conversion Factors Antifreeze-Based Combisystem #5 Using a Pool as a Heat Dump Product Information Pages 10% © Copyright 2009 Cert no. XXX-XXX-XXXX Caleffi North America, Inc. Printed: Milwaukee, Wisconsin USA Idronics#6 Feat_rev2.indd 2 5/4/10 2:57:57 PM SOLAR THERMAL COMBISYSTEMS 1. INTRODUCTION The energy savings potential of such systems will also be discussed. The goal is for designers to develop reasonable Most Americans are increasingly aware of rising energy expectations for what typical solar thermal combisystems prices and the environmental implications associated with can provide based on differences in climate, system size continued use of conventional fuels. “Sustainable living” and loads. is one of the most prevalent topics being discussed in a variety of media. 2. FUNDAMENTALS OF SOLAR COMBISYSTEM DESIGN This situation has created growing interest in renewable sources, such as sun, wind and biomass materials. It is The largest sector of the solar thermal market is domestic also fostering a rapidly expanding market for equipment water heating. This is true both in North America and that harvests this energy. worldwide. The underlying reason is the capacity to use solar energy on a year-round basis, and in particular, the Hydronics technology is the “glue” that holds most ability to collect solar energy when it is most abundant — in thermally based renewable energy systems together. summer. Solar thermal systems for heating domestic water Although heat sources such as solar collectors, solid-fuel were discussed in detail in idronics #3 (January 2008). boilers and geothermal heat pumps are indispensable components in such systems, they are not the sole A natural extension of a solar domestic water heating determinants of efficiency, energy yield or financial viability. system is adding capability to offset a portion of the Without proper heat conveyance, even the best renewable space heating load in the same building, and hence the energy heat source will not perform as expected. Thus, name “combisystem.” the proper application of modern hydronics technology is vital to the continued growth of the thermally based Most combisystems intended for residential applications renewable energy systems market. treat domestic water heating as the primary load, and thus take advantage of high solar energy availability in This issue of idronics focuses on systems that use solar summer. Beyond their DHW “base load,” combisystems energy, as well as an auxiliary energy source, to supply a typically use greater collector area and larger storage portion of the domestic hot water and space heating needs tanks to capture and contain additional energy that can of a building. Such configurations are commonly called offset a portion of the building’s space heating load. solar thermal combisystems. Several design variations will be introduced and discussed in the context of residential As with solar DHW systems, combisystems require a and light commercial building applications. In each case, reliable means of freeze protection, as well as an auxiliary state-of-the-art hydronic technology such as variable flow, energy device that supplies the energy required for manifold-based distribution, hydraulic separation, thermal uninterrupted delivery of hot water and space heating mass and precisely controlled zoning are used to enhance when solar heat gains cannot cover the load. the system’s energy efficiency, enabling it to deliver the same unsurpassed comfort, reliability and long life as that ESSENTIAL DESIGN PRINCIPLES: provided by a well-designed conventional hydronic system. The following design concepts are imperative to the Both piping and control aspects of solar combisystems success of a solar combisystem. Each will be discussed are illustrated and described. In many cases, the control in the context of specific system designs described later techniques are similar to those used in modern “non- in this issue. solar” hydronic systems. When properly applied, these techniques allow combisystems to smoothly transition • The cooler the solar collectors can operate, the higher between use of solar and auxiliary energy so that their efficiency, and the greater the amount of solar occupants experience no difference in comfort. energy they harvest. 3 Idronics#6 Feat_rev2.indd 3 5/4/10 2:57:59 PM • In an “ideal” solar thermal system, none of the heat The instantaneous thermal efficiency of a solar collector produced by the auxiliary heat source would enter the is defined as the ratio of the heat transferred to the solar storage tank. This prevents the auxiliary heat source fluid passing through the collector divided by the solar from increasing the temperature of the storage tank above radiation incident on the gross area of the collector, as what it would be based solely on solar energy input. Such shown in figure 2-1. heating, if allowed to occur, delays the startup of the solar collection cycle, and thus reduces the energy collected Instantaneous collector efficiency can be measured by during that cycle. recording the flow rate through the collector along with simultaneous