SIST EN 12977-2:2018
(Main)Thermal solar systems and components - Custom built systems - Part 2: Test methods for solar water heaters and combisystems
Thermal solar systems and components - Custom built systems - Part 2: Test methods for solar water heaters and combisystems
This European Standard applies to small and large custom built solar heating systems with liquid heat transfer medium for residential buildings and similar applications, and gives test methods for verification of the requirements specified in EN 12977-1.
This document also includes a method for thermal performance characterization and system performance prediction of small custom built systems by means of component testing and system simulation.
Furthermore, this document contains methods for thermal performance characterization and system performance prediction of large custom built systems.
This document applies to the following types of small custom built solar heating systems:
- systems for domestic hot water preparation only;
- systems for space heating only;
- systems for domestic hot water preparation and space heating;
- others (e.g. including cooling).
This document applies to large custom built solar heating systems, primarily to solar preheat systems, with one or more storage vessels, heat exchangers, piping and automatic controls and with collector array(s) with forced circulation of fluid in the collector loop.
This document does not apply to
- systems with a store medium other than water (e.g. phase- change materials),
- thermosiphon systems,
- integral collector-storage (ICS) systems.
Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil 2: Prüfverfahren für solar betriebene Warmwasserbereiter und solare Kombianlagen
Diese Europäische Norm gilt für kleine und große kundenspezifisch gefertigte thermische Solaranlagen mit flüssigem Wärmeträgermedium, die für den Einsatz in Wohnbauten und ähnliche Anwendungsfälle vorgesehen sind, und gibt Prüfverfahren für die Verifizierung der Erfüllung der in EN 12977-1:2018 festgelegten Anforderungen an.
Dieses Dokument enthält auch ein Verfahren für die Charakterisierung der Wärmeleistung und die Vorhersage der zu erwartenden Anlagenleistung kleiner kundenspezifisch gefertigter Anlagen durch Bauteilprüfung und Anlagensimulation.
Darüber hinaus enthält dieses Dokument Verfahren für die Charakterisierung der Wärmeleistung und die Vorhersage der zu erwartenden Anlagenleistung großer kundenspezifisch gefertigter Anlagen.
Dieses Dokument gilt für die folgenden Typen kleiner kundenspezifisch gefertigter thermischer Solaranlagen:
ausschließlich für die häusliche Trinkwassererwärmung verwendete Anlagen;
ausschließlich für die Raumheizung verwendete Anlagen;
für häusliche Trinkwassererwärmung und Raumheizung verwendete Anlagen;
sonstige Anlagen (z. B. einschließlich Kühlung).
Dieses Dokument gilt für große kundenspezifisch gefertigte thermische Solaranlagen, hauptsächlich für solare Vorwärmanlagen mit einem oder mehreren Speichern, Wärmeübertragern, Rohrleitungen und automatischen Reglern und einer oder mehreren Kollektorgruppen mit erzwungener Umwälzung des Fluids im Kollektorkreislauf.
Dieses Dokument gilt nicht für
Anlagen, die ein anderes Speichermedium als Wasser verwenden (z. B. Phasenwechselmaterial),
Thermosiphon-Anlagen,
integrierte Kollektor-Speicher(ICS)-Anlagen.
Installations solaires thermiques et leurs composants - Installations assemblées à façon - Partie 2 : Méthodes d'essai pour chauffe-eau solaires et installations solaires combinées
La présente Norme européenne s’applique aux petites et grandes installations de chauffage solaire assemblées à façon, à liquide caloporteur, utilisées dans les bâtiments résidentiels et applications similaires, et il présente des méthodes d’essai permettant de vérifier les exigences spécifiées dans l’EN 12977-1:2018.
Le présent document comprend également une méthode de caractérisation des performances thermiques et de prévision des performances des petites installations assemblées à façon à l’aide d’essais des composants et de simulation de l’installation.
Par ailleurs, le présent document contient des méthodes pour la caractérisation des performances thermiques et la prévision des performances des grandes installations assemblées à façon.
Le présent document s’applique aux types suivants de petites installations de chauffage solaire assemblées à façon :
— installations pour la production d’eau chaude sanitaire exclusivement ;
— installations pour le chauffage des locaux uniquement ;
— installations pour la production d’eau chaude sanitaire et le chauffage des locaux ;
— autres (par exemple, y compris le refroidissement).
Le présent document s’applique aux grandes installations de chauffage solaire assemblées à façon, principalement aux installations à préchauffage, munies d’une ou de plusieurs cuves de stockage, échangeurs de chaleur, canalisations et dispositifs de régulation automatique, et d’un ou de plusieurs champs de capteurs à circulation forcée de fluide dans la boucle de captage.
Le présent document ne s’applique pas aux :
— installations ayant un autre milieu de stockage que l’eau (par exemple, matériaux à changement de phase) ;
— installations à thermosiphon ;
— installations à capteurs autostockeurs (ICS).
Toplotni sončni sistemi in sestavni deli - Neserijsko izdelani sistemi - 2. del: Preskusne metode za sončne grelnike vode in kombinirane sisteme
Ta evropski standard se uporablja za majhne in velike neserijsko izdelane sončne ogrevalne sisteme s tekočim sredstvom za prenos toplote za stanovanjske zgradbe in podobne uporabe ter določa preskusne metode za preverjanje zahtev iz standarda EN 12977-1.
Dokument vsebuje tudi metodo za opredelitev toplotne učinkovitosti in predvidevanje sistemske učinkovitosti majhnih neserijsko izdelanih sistemov s pomočjo preskušanja sestavnih delov in simulacije sistema.
Poleg tega dokument vsebuje metode za opredelitev toplotne učinkovitosti in predvidevanje sistemske učinkovitosti velikih neserijsko izdelanih sistemov.
Ta dokument se uporablja za naslednje vrste majhnih neserijsko izdelanih sončnih ogrevalnih sistemov:
– sistemi, namenjeni izključno pripravi tople vode v gospodinjstvih;
– sistemi, namenjeni izključno segrevanju prostorov;
– sistemi, namenjeni pripravi tople vode v gospodinjstvih in segrevanju prostorov;
– drugi sistemi (npr. vključno s hlajenjem).
Ta dokument se uporablja za velike neserijsko izdelane sončne ogrevalne sisteme, predvsem za sončne predogrevalne sisteme, z eno ali več posodami za shranjevanje, toplotnimi prenosniki, ocevjem in samodejnim krmiljenjem ter kolektorskimi polji s prisilnim kroženjem tekočine v zanki kolektorja.
Ta dokument se ne uporablja za:
– sisteme, ki kot sredstvo shranjevanja uporabljajo druga sredstva namesto vode (npr. fazno spremenljive materiale);
– termosifonske sisteme;
– sisteme integralnega kolektorskega shranjevanja (ICS).
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil 2: Prüfverfahren für solar betriebene Warmwasserbereiter und solare KombianlagenInstallations solaires thermiques et leurs composants - Installations assemblées à façon - Partie 2 : Méthodes d'essai pour chauffe-eau solaires et installations solaires combinéesThermal solar systems and components - Custom built systems - Part 2: Test methods for solar water heaters and combisystems91.140.65Oprema za ogrevanje vodeWater heating equipment91.140.10Sistemi centralnega ogrevanjaCentral heating systems27.160Solar energy engineeringICS:Ta slovenski standard je istoveten z:EN 12977-2:2018SIST EN 12977-2:2018en,fr,de01-september-2018SIST EN 12977-2:2018SLOVENSKI
STANDARDSIST EN 12977-2:20121DGRPHãþD
SIST EN 12977-2:2018
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12977-2
April
t r s z ICS
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{ sä s v rä s râ
{ sä s v rä x w Supersedes EN
s t { y yæ tã t r s tEnglish Version
Thermal solar systems and components æ Custom built systems æ Part
tã Test methods for solar water heaters and combisystems Installations solaires thermiques et leurs composants æInstallations assemblées à façon æ Partie
t ã Méthodes d 5essai pour chauffeæeau solaires et installations solaires combinées
Thermische Solaranlagen und ihre Bauteile æ Kundenspezifisch gefertigte Anlagen æ Teil
tã Prüfverfahren für Solaranlagen zur Trinkwassererwärmung und solare Kombianlagen This European Standard was approved by CEN on
t { October
t r s yä
egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä
translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä
CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Serbiaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey and United Kingdomä
EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Rue de la Science 23,
B-1040 Brussels
9
t r s z CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN
s t { y yæ tã t r s z ESIST EN 12977-2:2018
EN 12977-2:2018 (E) 2 Contents Page European foreword . 4 Introduction . 5 1 Scope . 8 2 Normative references . 8 3 Terms and definitions . 9 4 Symbols and abbreviations . 9 5 System classification . 12 6 Test methods . 12 6.1 Introduction . 12 6.2 General . 12 6.2.1 Suitability for drinking water . 12 6.2.2 Water contamination . 12 6.2.3 Freeze resistance . 12 6.2.4 High-temperature protection . 12 6.2.5 Reverse circulation prevention . 12 6.2.6 Pressure resistance . 12 6.2.7 Electrical safety . 13 6.3 Materials . 13 6.4 Components and pipework . 13 6.4.1 Collector and collector array . 13 6.4.2 Supporting frame . 13 6.4.3 Collector and other loops . 13 6.4.4 Circulation pump . 13 6.4.5 Expansion vessels . 13 6.4.6 Heat exchangers . 14 6.4.7 Store . 14 6.4.8 Pipework . 14 6.4.9 Thermal insulation . 14 6.4.10 Control equipment . 14 6.5 Safety equipment and indicators. 15 6.5.1 Safety valves . 15 6.5.2 Safety lines and expansion lines . 15 6.5.3 Blow-off lines . 15 6.5.4 Store isolation valve . 15 6.5.5 Indicators . 15 6.6 Installation . 16 6.6.1 Roof tightness . 16 6.6.2 Lightning . 16 6.6.3 Snow and wind loads . 16 6.7 Initial operation, inspection and commissioning . 16 6.8 Documentation . 16 6.9 System performance (for small systems only) . 16 6.10 Water wastage (for small systems only) . 16 7 Optional performance test of small custom built solar heating systems . 16 7.1 General . 16 SIST EN 12977-2:2018
EN 12977-2:2018 (E) 3 7.2 Test of the solar collector . 17 7.3 Test of the water store(s) . 18 7.4 Test of the control equipment . 18 7.5 Determination of the hot water comfort . 18 7.6 System simulation model. 18 7.7 Long-term performance prediction . 18 7.7.1 General . 18 7.7.2 Calculation procedure. 19 7.7.3 Prediction of yearly system performance indicators . 19 7.7.4 Calculation of the net auxiliary energy demand and fractional energy savings for solar-plus-supplementary systems . 19 7.7.5 Calculation of the solar fraction for solar-only and preheat systems . 22 7.7.6 Calculation of the parasitic energy (for all system types) . 23 7.8 Presentation of performance indicators . 23 8 Performance test report . 25 Annex A (normative)
Reference conditions for performance prediction . 26 Annex B (normative)
Additional information regarding the calculation of the fractional energy savings . 35 Annex C (informative)
Short-term system testing . 37 Annex D (informative)
Long-term monitoring . 49 Annex E (informative)
Determination of water wastage . 51 Annex F (informative)
Implementation for Ecodesign and Energy Labelling . 52 Annex ZA (informative)
Relationship between this European Standard and the energy labelling requirements of Commission Delegated Regulation (EC) No 811/2013 aimed to be covered . 53 Annex ZB (informative)
Relationship between this European Standard and the energy labelling requirements of Commission Delegated Regulation (EC) No 812/2013 aimed to be covered . 54 Annex ZC (informative)
Relationship between this European Standard and the ecodesign requirements of Commission Regulation (EC) No 814/2013 aimed to be covered . 55 Bibliography . 56
SIST EN 12977-2:2018
EN 12977-2:2018 (E) 4 European foreword This document (EN 12977-2:2018) has been prepared by Technical Committee CEN/TC 312 “Thermal solar systems and components”, the secretariat of which is held by ELOT. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2018, and conflicting national standards shall be withdrawn at the latest by October 2018. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 12977-2:2012. This document has been prepared under the Mandate M/534 “Standardisation request to the European standardisation organisations pursuant to Article 10(1) of Regulation (EU) No 1025/2012 of the European Parliament and of the Council in support of implementation of Commission Regulation (EU) No 814/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for water heaters and hot water storage tanks and Commission Delegated Regulation (EU) No 812/2013 of 18 February 2013 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to the energy labelling of water heaters, hot water storage tanks and packages of water heater and solar device” which was given to CEN by the European Commission and the European Free Trade Association. For relationship with EU Directive(s), see informative Annex ZA, ZB and ZC, which are integral parts of this document. EN 12977 is currently composed with the following parts: — Thermal solar systems and components — Custom built systems — Part 1: General requirements for solar water heaters and combisystems; — Thermal solar systems and components — Custom built systems — Part 2: Test methods for solar water heaters and combisystems; — Thermal solar systems and components — Custom built systems — Part 3: Performance test methods for solar water heater stores; — Thermal solar systems and components — Custom built systems — Part 4: Performance test methods for solar combistores; — Thermal solar systems and components — Custom built systems — Part 5: Performance test methods for control equipment. According to the CEN-CENELEC Internal Regulations, the national standards organisations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 12977-2:2018
EN 12977-2:2018 (E) 5 Introduction a) Drinking water quality In respect of potential adverse effects on the quality of drinking water intended for human consumption caused by the product covered by this document, it should be noted that 1) this document provides no information as to whether the product may be used without restriction in any of the Member States of the EU or EFTA, 2) while awaiting the adoption of verifiable European criteria, existing national regulations concerning the use and/or the characteristics of this product remain in force. b) Factory made and custom built solar heating systems EN 12976-1:2017, EN 12976-2:2017, EN 12977-1:2018, EN 12977-2:2018, EN 12977-3:2018, EN 12977-4:2018 and EN 12977-5:2018 distinguish two categories of solar heating systems: 1) factory made solar heating systems; and 2) custom built solar heating systems. The classification of a system as factory made or custom built is a choice of the final supplier, in accordance to the following definitions. 3) Factory made solar heating systems are batch products with one trade name, sold as complete and ready to install kits, with fixed configurations. Systems of this category are considered as a single product and assessed as a whole. If a factory made solar heating system is modified by changing its configuration or by changing one or more of its components, the modified system is considered as a new system. Requirements and test methods for factory made solar heating systems are given in EN 12976-1:2017 and EN 12976-2:2017. 4) Custom built solar heating systems are either uniquely built or assembled by choosing from an assortment of components. Systems of this category are regarded as a set of components. The components are separately tested and test results are integrated to an assessment of the whole system. Requirements for custom built solar heating systems are given in EN 12977-1:2018, test methods are specified in EN 12977-2:2018, EN 12977-3:2018, EN 12977-4:2018 and EN 12977-5:2018. Custom built solar heating systems are subdivided into two categories: i) large custom built systems are uniquely designed for a specific situation. In general, they are designed by HVAC engineers, manufacturers or other experts; ii) small custom built systems offered by a company are described in a so-called assortment file, in which all components and possible system configurations, marketed by the company, are specified. Each possible combination of a system configuration with components from the assortment is considered as one custom built system. Table 1 shows the division for different system types. SIST EN 12977-2:2018
EN 12977-2:2018 (E) 6 Table 1 — Division for factory made and custom built solar heating systems Factory made solar heating systems (EN 12976–1:2017 and EN 12976–2:2017) Custom built solar heating systems (EN 12977–1:2018, EN 12977–2:2018, EN 12977–3:2018, EN 12977–4:2018 and EN 12977–5:2018) Integral collector-storage systems for domestic hot water preparation Forced circulation systems for hot water preparation and/or space heating/cooling, assembled using components and configurations described in a documentation file (mostly small systems) Thermosiphon systems for domestic hot water preparation Forced circulation systems as batch product with fixed configuration for domestic hot water preparation Uniquely designed and assembled systems for hot water preparation and/or space heating/cooling (mostly large systems) NOTE 1 Forced circulation systems can be classified either as factory made or as custom built, depending on the market approach chosen by the final supplier. NOTE 2 Both factory made and custom built systems are performance tested under the same set of basic reference conditions as specified in EN 12976–2:2017, Annex B and in EN 12977–2:2018, Annex A. In practice, the installation conditions may differ from these reference conditions. c) Test methods and procedures for the analysis of large custom built solar heating systems Quality assurance is of primary importance for large custom built systems. The total investment cost for such systems is higher than for smaller ones, although the specific investment cost (i.e. per m2 collector area) is lower. In several European countries, the potential of large custom built systems from the point of view of conventional energy savings is much larger than for smaller ones. Moreover, the return on investment is in many cases more favourable for large systems than for small ones. Hence, both the purchasers of large custom built systems and the governments are interested in efficient, reliable and durable systems, the thermal performance of which may be accurately predicted, checked and supervised. The test methods in this document provide a means of verifying the compliance of large custom built systems with the requirements in EN 12977-1:2018. NOTE 3 Within the framework of the EU ALTENER Programme the project “Guaranteed Solar Results” (GSR) was addressing similar objectives in respect of quality assurance (see [7], [8]). Similar procedures and monitoring equipment were used as described in Annexes C and D. It might be necessary to update Annexes C and D at a later stage during a revision of this document when more expertise is available. As large custom built systems are by definition unique systems, only general procedures on how to check and supervise them may be given. An additional difficulty in the formulation of procedures is the fact that they have to be adapted to the dimension of the large custom built system considered, which may vary from typically 30 m2 to 30 000 m2 of collector area. Therefore, several possible levels of analysis are included (Annexes C and D). The objective of the two short-term system tests presented in Annex C is the characterization of system performance and/or the estimation of the ability of the system to deliver the energy claimed by the designer. In principle, two approaches for short-term system testing are referred to in this European Standard: SIST EN 12977-2:2018
EN 12977-2:2018 (E) 7 1) a simplified check of short-term system performance, carried out by intercomparison of the measured solar heating system heat gain with the one predicted by simulation, using the actual weather and operating conditions as measured during the short-term test; 2) a short-term test for long-term system performance prediction. The performance of the most relevant components of the solar heating system is measured for a certain time period while the system is in normal operation. More detailed measurements encompass i) energy gain of collector array(s) and ii) energy balance over storage vessel(s). Inter-comparison of the observed and simulated energy quantities provides the indirect validation of collector and storage design parameters. The measured data within the collector array are also used for direct identification of the collector array parameters. As far as the component parameters are verified, the long-term prediction of the system gain as well as the detection of possible sources of system malfunctioning are possible. Annex D describes a procedure for long-term monitoring as a part of the supervision of a large custom built solar heating system. The objectives of supervision may be: 1) the early recognition of possible failures of system components, in order to get the maximum benefit from the initial solar investment as well as to minimize the consumption of non-solar energy and the resulting environmental impact, 2) the measurement of system performance (solar gains or other system indicators), if requested by a contractual clause, e.g. guaranteed results. The long-term monitoring in Annex D is limited to the solar energy specific aspects, especially to the determination of the solar contribution to the total heat load. Instrumentation used in the long term monitoring should be an integrating part of the system, a part included from the very beginning of the design process. If adequately foreseen, it may also be used for system adjustment at start time. SIST EN 12977-2:2018
EN 12977-2:2018 (E) 8 1 Scope This European Standard applies to small and large custom built solar heating systems with liquid heat transfer medium for residential buildings and similar applications, and gives test methods for verification of the requirements specified in EN 12977-1:2018. This document also includes a method for thermal performance characterization and system performance prediction of small custom built systems by means of component testing and system simulation. Furthermore, this document contains methods for thermal performance characterization and system performance prediction of large custom built systems. This document applies to the following types of small custom built solar heating systems: — systems for domestic hot water preparation only; — systems for space heating only; — systems for domestic hot water preparation and space heating; — others (e.g. including cooling). This document applies to large custom built solar heating systems, primarily to solar preheat systems, with one or more storage vessels, heat exchangers, piping and automatic controls and with collector array(s) with forced circulation of fluid in the collector loop. This document does not apply to — systems with a store medium other than water (e.g. phase- change materials), — thermosiphon systems, — integral collector-storage (ICS) systems. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 307, Heat exchangers - Guidelines to prepare installation, operating and maintenance instructions required to maintain the performance of each type of heat exchangers EN 806-1, Specifications for installations inside buildings conveying water for human consumption - Part 1: General EN 809, Pumps and pump units for liquids — Common safety requirements EN 1991-1-3, Eurocode 1 - Actions on structures - Part 1-3: General actions - Snow loads EN 1991-1-4, Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions EN 12975-1:2006+A1:2010, Thermal solar systems and components - Solar collectors - Part 1: General requirements EN 12976-1:2017, Thermal solar systems and components - Factory made systems - Part 1: General requirements SIST EN 12977-2:2018
EN 12977-2:2018 (E) 9 EN 12976-2:2017, Thermal solar systems and components - Factory made systems - Part 2: Test methods EN 12977-1:2018, Thermal solar systems and components — Custom built systems — Part 1: General requirements for solar water heaters and combisystems EN 12977-3:2018, Thermal solar systems and components — Custom built systems — Part 3: Performance test methods for solar water heater stores EN 12977-4:2018, Thermal solar systems and components — Custom built systems — Part 4: Performance test methods for solar combistores EN 12977-5:2018, Thermal solar systems and components — Custom built systems — Part 5: Performance test methods for control equipment EN 16297-1, Pumps - Rotodynamic pumps - Glandless circulators - Part 1: General requirements and procedures for testing and calculation of energy efficiency index (EEI) EN 60335-1, Household and similar electrical appliances — Safety — Part 1: General requirements (IEC 60335-1) EN ISO 9488:1999, Solar energy - Vocabulary (ISO 9488:1999) EN ISO 9806:2013, Solar energy - Solar thermal collectors - Test methods (ISO 9806:2013) ISO 9459-5:2007, Solar heating — Domestic water heating systems — Part 5: System performance characterization by means of whole-system tests and computer simulation ISO/TR 10217, Solar energy — Water heating systems — Guide to material selection with regard to internal corrosion 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12975-1:2006+A1:2010, EN 12976-1:2017, EN 12977-1:2018, EN 12977-3:2018, EN 12977-5:2018, ISO 9459-5:2007 and EN ISO 9488:1999 apply. 4 Symbols and abbreviations For the purposes of this document, the following symbols and abbreviations apply. Table 2 — Symbols, definition and unit Symbol Definition Unit a1 heat loss coefficient at (Ím – Ía) = 0 W/(m2 × K) Ac reference area of collector m2 Cc effective thermal capacity of collector or collector array J/K Day day number of the year
Ds shift term for the calculation of mains water temperature at reference location
fsav fractional energy savings % SIST EN 12977-2:2018
EN 12977-2:2018 (E) 10 Symbol Definition Unit fsol solar fraction % Gd diffuse solar irradiance on tilted plane W/m2 Gg global solar irradiance (on horizontal plane) W/m
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