CoP Solar thermal Legionella
Contents
1. between Auxiliary heater a source of heat other than solar used to supplement the output provided by the solar en ergy system Solar water heater Solar water heater Solar only C B bi C W a generic term to designate a solar thermal system of type preheat system with auxiliary heater solar as sisted hot water system or solar only system Solar assisted hot water system solar preheat A r Auxiliary heater BaS Solar only system a solar water heater without any auxiliary heat source solat plus supplementary Solar assisted hot water system C g W Auxiliary heater a generic term to designate a solar preheat sys tem and its series connected water heater or a Figure 1 Graphical representation of the solar plus supplementary system A solar assist different solar water heater types c cold water w warm water ed hot water system has a non solar water heat ing part named auxiliary part and a solar heating part There are various possible in teractions between the two parts Solar preheat system a solar hot water system to preheat water or air prior to its entry into any other type of water or air heater Solar plus supplementary system a solar heating system that utilizes both solar and auxiliary energy sources in an in tegrated way and is able to provide a specified heating service independent of solar energy availability Application the way that the solar wa2. ing from the heat storage tank Page 12 of 26 Code of practice solar water heaters and Legionella 23 04 2013 The following give recommendations on all combinations of functions and types 5 1 System designs Type Recommendations Type Recommendations Type Recommendations Type Recommendations Solar heating Auxiliary heating Instantaneous None R 1 according to CEN TR 16355 Storage type gi J a Fae a R 2 for low risk application or R 3 for medium or high risk applications Risk levels according to Table 1 Storage type R4 or R 2 for low risk application or R 3 for medium or high risk applications Instantaneous q Storage type Instantaneous Storage type Risk levels are according to Table 1 see paragraph 5 2 for an expla nation of R1 R2 R3 and R4 Page 13 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Table 1 Building categories and risk levels 1 based on SIA 385 1 CH Risk Level low medium high Building Category Single family housing Residential apartment building without central hot water supply Administration Schools without showers Sale Restaurants Meeting rooms Stores repositories Residential apartment building with central hot water supply Schools with showers Ho
3. The recommendations are structured in four different configurations representing all combina tions of the functions of the solar and auxiliary heating Solar heating Auxiliary heating Storage type Solar heat is accumulated ina Auxiliary heat is accumulated in a storage tank filled with potable storage tank filled with potable wa water ter Instantaneous type Solar heat is transferred to the The potable water is contained in a potable water through a heat heat exchanger directly or indirect exchanger not integrated in a ly heated by a heater buffer tank The solar and auxiliary functions can be separate in two tanks or combined in one heat storage tank CEN TR 16355 gives recommendations on both the hot water installation as a whole and the components that heat up the potable water The following paragraphs focus on the compo nents It is assumed that the CEN TR 16355 recommendations on the installation as a whole are applied The following recommendation applies to all heat exchangers used as instantaneous water heaters Recommendation When an external heat exchanger is used as an instantaneous heater the pump in the loop should be controlled so that the water is allowed to cool down in periods without draw off The heat exchanger is not insulated The potable water should be heated in the heat exchanger in a single pass A heat trap should be applied to prevent the heat exchanger from convective heat
4. a C Use materials and inner surface finishing of the heat storage tank in conformity with the requirements in use in the food industry Use materials in accordance with national and European standards for materials being in contact with potable water 2002 359 EG and national implementations thereof The following materials are recommended stainless steel copper or enamelled steel 2 Design of heat storage tank holding potable water 3 4 a b d Design the tank in such a way that the complete potable water volume is affected dur ing draw off The storage tank design should be such that also the bottom part of the storage tank can be heated to at least 60 C When a heat exchanger is applied the lowest part of the heat exchanger should not be more than 5 cm above the lowest part of the storage tank For storage tanks with a potable water volume greater than 400 litres incorporate an inspection hatch at the bottom of the tank to enable the regular removal of deposits Minimize or prevent the use of sacrificial anodes and internal threaded female screw joints Controller a b Limit the setting of the maximum potable water storage tank temperature to 80 C to prevent deposition of lime Depending on the local potable water hardness this tem perature setting may be lower or higher 10 C Install a device that signals any malfunction of the system to the user especially that of the sola
5. pneumophila in a human macrophage like U937 cell line Microb Pathog 5 87 95 Rogers J Dowsett A B Dennis P J Lee J V and Keevil C W 1994a Influence of Plumbing Materials on Biofilm Formation and Growth of Legionella pneumophila in Potable Water Systems Applied and Environmental Microbiology 60 1842 1851 Rogers J Dowsett A B Dennis P J Lee J V and Keevil C W 1994b Influence of temperature and plumbing material selection on biofilm formation and growth of Legionella pneumophila in a model potable water system containing complex microbial flora Applied and Environmental Microbiology 60 1585 1592 Saby S Vidal A and Suty H 2005 Resistance of Legionella to disinfection in hot water distribution systems Water Sci Technol 52 15 28 Schulze Robbecke R Rodder M and Exner M 1987 Multiplication and killing temperatures of naturally occurring legionellas Zentralbl Bakteriol Mikrobiol Hyg B 184 495 500 Stout J E Best M G and Yu V L 1986 Susceptibility of members of the family Legionellaceae to thermal stress implications for heat eradication methods in water distribution systems Applied and Environmental Microbiology 52 396 399 Surman Lee S Fields B Hornei B Ewig S Exner M Tartakovskii I Lajoie L Dangendorf F Bentham R Cabanes P A Fourrier P Trouvet T and Wallet F 2007 Ecology and environmental sources of Legionella In Legionella and the Prevention of
6. 400 litres the sediment from the storage tank and any scale within the tank should be removed in accordance with the local conditions but at least once a year Recommendation Solar preheat systems applied in a hot water system with circulation of hot or mixed water to maintain part of the distribution lines at high temperature should be connected in such a way that in summer the solar heat can be used to compensate for the heat losses of the circulation loop Recommendation 8 This mixing valve is required by EN 12976 1 and EN 12977 1 A thermostatic mixing valve aimed at reducing the hot water temperature to a comfortable temperature of use should always be located as close as possible to the user s draw off point Page 25 of 26 Code of practice solar water heaters and Legionella 23 04 2013 In solar assisted hot water systems circulation of blended water should be avoided and the distribution temperature should be set such that 30 s after fully opening a draw off valve the water temperature should not be less than 60 C according to EN 806 2 Page 26 of 26
7. 6 4 Sampling procedure to check for Legionella eee eeeececeeeeeneeeeeenneeeeeeneeeeeenaeeeeeeaas 18 Annex A Consp d Tt CTetUe oo cccceeeceeccceeseecceneeccaceeneseacenseencceeneecdenseeacceuteeeaceneneacecenseeaecentes 19 ANNEX B informative Solar only systems 0 ccccceeeeeeeeeeeeeeeeeeeeeeeteeeeeeeseeeaeeesenaeeeeseaeeees 21 ANNEX C informative Non thermal disinfection techniques ccceceeeeceeeeteeeeeeetteeeeees 23 ANNEX D informative Good practice for solar assisted hot water systemS ceeee 25 Page 3 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Foreword The authors of the report have in depth expertise in hot water systems solar thermal systems and Legionella ecology and control The recommendations are based on in depth knowledge experience and published evidence In order to reach agreement on the recommendations amongst concerned parties potable water authorities and solar thermal industry further ac tions are needed The draft report should be offered to both the CEN TC 164 and CEN TC 312 for discussion fine tuning and ultimately for acceptance It would be most efficient if this is done in a common ad hoc working group of both TC s However if this is not possible the draft report could be handled by the CEN TC 312 alone The Code of practice is mostly based on the report Legionella and solar water heaters This report co
8. meer eerie ar area sere Peg errr ec ert rry ereree te Perec E a ce reer reer eer ener 6 2 RENONS nani A ated tailed ed 7 2 1 Normative FETCRENCOS csetecdec caved ctedet ne cedetene edocs dbacdeveede cadveicuetenyeeccuecteaactecvine cess uveienes setae 7 2 2 Other reterenCes via sictecesteccec eeskiceestutseerestee sd ntees a ae E EE cess nee 7 3 Terms and definitions 0 00 eee eeeeeeeeeeeeee ee ee eeee ee eeenee ee eee eM eee RS phe eeeee 8 4 Recommendations applicable to all solar water NEaters c cc cccccceececeecceceeeeeeseeeeeeeeeees 10 5 Recommendations applicable to solar assisted hot water systeMS cceeeeeeeees 12 5 1 System ASSIGNS sosssdenssss esisi a ND a aaan ae saiia KANER 13 5 2 Recommendations on system CGeSIQNS cece eeeeeeteenceeeeeeeeaeeeeeeaaeeeeeeaeeeseenateeeeeas 14 6 MethOdSiz icicisistadeistisadiistetceeilateceeatilecssac A E EA 16 6 1 Intrinsic frequent thermal disinfection ccccccceeceeeeceeceeeeeeeseceeeaeeeeeeeeeseesnnaeeneees 16 6 2 Forced thermal disinfection of a storage tank seessseseesseerssserrsserrrssrrrrssrerrssreens 16 6 3 Devices to detect malfunctioning 0 eee eeecceceeeene eee eeetneeeeetaeeeeetaeeeseeaeeeeetnaeeeeeeaees 17 6 3 1 Malfunctioning of the Collector loop 0 0 0 ceeeeeteeeeeeeeeeeeeeeeneeeeetiieeeeetaeeeeetneeeereaea 17 6 3 2 Malfunctioning of the auxiliary heating part c ce eecceeeeeeteeeeeenteeeeeeteeeeeeneeeeeeaas 17
9. Legionellosis ed Bartram J Chartier Y Lee J V Pond K and Surman Lee S pp 29 38 Geneva WHO Page 20 of 26 Code of practice solar water heaters and Legionella 23 04 2013 ANNEX B informative Solar only systems In a solar only system a minimum hot water temperature cannot be ensured If such a system is fitted with a so called electrical emergency heater this is only to prevent the risk of freezing EN ISO 9488 states that the electrical heater has to be turned off for at least 315 days a year This type of system has a potential Legionella risk due to the mid level temperature in the storage tank during operation and the lack of thermal disinfection capacity by an auxiliary heater For that reason such solar water heaters should not be applied in high risk applica tions Table 1 Due to the fact that solar only systems are not equipped with an auxiliary heater the hot water is used on average at a lower demand temperature Assuming that the same heat quantity is needed in both solar only and preheat systems this means that solar only systems effectively show a higher water throughput This effect is comparable with a preheat system with an under dimensioned tank volume implying a lesser vulnerability for high concentrations of Legionella in the tank The absence of an auxiliary heater on the one hand makes a solar only system more vulnera ble to Legionella growth whereas the higher annual water throughput coul
10. N 806 2 60 C and many national regulations within Europe As such solar only systems are not generally allowed within Europe are not relevant for the CEN TR 16355 report and do not fall within the scope of the present report For informative purpose Annex B gives recommendations for their safe use Page 5 of 26 Code of practice solar water heaters and Legionella 23 04 2013 1 Scope This code of practice provides recommendations on solar assisted hot water systems that min imize the risk of Legionella infection by the user of and others exposed to the system For the sake of completeness recommendations on solar only systems although out of the scope of the CEN TR 16355 technical report are provided in Annex B This report is limited to solar assisted hot water systems with a solar collector that uses a liquid as the heat transfer fluid and is equipped with a transparent cover and with one solar heat storage tank with a volume dedicated to the storage of solar thermal energy larger than 25 litres per square metre solar collector aperture This report supplements the CEN TR 16355 technical report Page 6 of 26 Code of practice solar water heaters and Legionella 23 04 2013 2 References 2 1 Normative references EN 806 1 EN 806 2 EN ISO 9488 EN 12976 1 EN 12977 1 2002 359 EG SIA 385 1 Specifications for installations inside buildings conveying water for human con sumpt
11. a species serogroups and monoclonal subgroups in hot water systems in south eastern Germany Zentralbl Hyg Umweltmed 193 450 460 Makin T 2009 Legionella bacteria and solar pre heating of water for domestic purposes Report for the Water Regulations Advisory Scheme http www wras co uk PDF_Files Preheated_Water_Report pdf Mathys W Stanke J Harmuth M and Junge Mathys E 2008 Occurrence of Legionella in hot water systems of single family residences in suburbs of two German cities with special reference to solar and district heating Int J Hyg Environ Health 211 179 185 Mauchline W S James B W Fitzgeorge R B Dennis P J and Keevil C W 1994 Growth temperature reversibly modulates the virulence of Legionella pneumophila nfect Immun 62 2995 2997 Mouchtouri V Velonakis E and Hadjichristodoulou C 2007a Thermal disinfection of hotels hospitals and athletic venues hot water distribution systems contaminated by Legionella species Am J Infect Control 35 623 627 Mouchtouri V Velonakis E Tsakalof A Kapoula C Goutziana G Vatopoulos A Kremastinou J and Hadjichristodoulou C 2007b Risk factors for contamination of hotel water distribution systems by Legionella species Applied and Environmental Microbiology 73 1489 1492 Page 19 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Pearlman E Jiwa A H Engleberg N C and Eisenstein B 1988 Growth of Legionella
12. charge to waste Allowance exemption from authorities potable water and environment Extra installation parts dosing system Maintenance refills of dosing system Remarks noticeable by taste and smell and high doses are corrosive for copper piping and possibly some plastics 2 Chlorine dioxide dosing CIO3 Chlorine dioxide can be generated in a number of ways and is a recognised means of treating water to help control the growth of legionellae Like chlorine it can be used continuously at a low concentration up to 0 5 mg L to inhibit microbial growth or as a single shot high disin fecting concentration of up to 20 mg L for 2 to 3 hours The ClO will treat all downstream parts of the system as well as the tanks and is not affected by pH or temperature to the same degree as chlorine The limit for treating potable water in some countries is 0 5 mg L and this low level is not always effective at controlling Legionella in contaminated systems Prolonged continu ous dosing at 2 mg L has been used to control legionellae in colonised water systems Allowance exemption from authorities potable water and environment Extra installation parts dosing system Maintenance refills of dosing system Remarks Some plastics may be damaged by chlorine dioxide Page 23 of 26 Code of practice solar water heaters and Legionella 23 04 2013 3 Chloramine dosage CINH gt 2 Monochloramine up to 2 mg L is used to disinfect potable water but eq
13. cient auxiliary heating and react accord ingly Option 2 Malfunctioning could also be communicated to the user by means of a warning light situated in a location clearly visible to the user 6 4 Sampling procedure to check for Legionella The following method gives global recommendations on how to perform a sample test for Le gionella in the hot water system In literature and national regulations and standards more detailed methods are described Sampling frequency based on an adequate risk analysis but should be at least once every three months Sample points 30 of the draw off points Sampling location draw off points 1 seldom used 2 preferably at shower draw off point and at a distant location from the hot water heating device Page 18 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Annex A Consulted literature Anon 2010 BS 8580 Water Quality Risk Assessments for Legionell control Code of Practice London British Standards Institute Bagh L K and Ellehauge K 2001 Bacterial growth in solar heating prepared and traditional tanks International Energy Agency Solar Heating amp Cooling Programme Dennis P J Green D and Jones B P 1984 A note on the temperature tolerance of Legionella Journal of Applied Bacteriology 56 349 350 Horwitz M A and Silverstein S C 1980 Legionnaires disease bacterium Legionella pneumophila multiples intracellularly in human monocyt
14. d mitigate this risk Overall it is defendable to apply the same rules as for preheat systems to a solar only system In order to minimize the risk of Legionella growth the following recommendations are given Recommendation B 1 A warning should be included in the user manual with the following text For thermosyphon systems The system is vulnerable to the risk of Legionella growth when not in use during a period of more than 14 days in winter time The system is not vulnerable again when the heat storage tank is heated up above 55 C For systems with forced circulation in the collector loop When absent for more than 14 days during the winter time the collector pump or the col lector pump controller should be disconnected to safeguard against Legionella vulnerabil ity Recommendation B 2 For all solar only systems not fulfilling the recommendations of Recommendation B 1 The components of the solar only system should be sized as such that Page 21 of 26 Code of practice solar water heaters and Legionella 23 04 2013 the volume of the heat storage tank is smaller or equal to the designed daily hot water consumption the ratio Veto Aco l m should conform to table 2 a system inspection should verify that the system design is such that the bottom part of the storage tank can be heated by the solar heat An integrated heat exchanger should be applied according to chapter 4 point 2b Recommendatio
15. es J Clin Invest 66 441 450 Hospedales C J Joseph C Lee J Lewis Bell K Michael L and Francis M 1997 International investigation of an outbreak of Legionnaires Disease at a major hotel associated with potable water Antigua 1996 pp 31 HSE 2000 Legionnaires disease the control of legionella bacteria in water systems Approved Code of Practice and Guidance Sudbury HSE Books Konishi T Yamashiro T Koide M and Nishizono A 2006 Influence of temperature on growth of Legionella pneumophila biofilm determined by precise temperature gradient incubator J Biosci Bioeng 101 478 484 Levin A S Caiaffa Filho H H Sinto S I Sabbaga E Barone A A and Mendes C M 1991 An outbreak of nosocomial Legionnaires disease in a renal transplant unit in Sao Paulo Brazil Legionellosis Study Team J Hosp Infect 18 243 248 Levin A S Gobara S Scarpitta C M Warschauer C L Sinto S Rodrigues E Mendes C M Sabbaga E and Boulos M 1995 Electric showers as a control measure for Legionella spp in a renal transplant unit in Sao Paulo Brazil Legionellosis Study Team J Hosp Infect 30 133 137 Loret J F Robert S Thomas V Cooper A J McCoy W F and Levi Y 2005 Comparison of disinfectants for biofilm protozoa and Legionella control J Water Health 3 423 433 Luck P C Leupold Hlawitschka M Helbig J H Carmienke Jatzwauk L and Guderitz T 1993 Prevalence of Legionell
16. fter the heat storage tank If the incoming water were heavily contaminated a small proportion of cells may survive passage through the UV unit and colonise the system downstream of the UV unit Allowance No information available Extra installation parts UV light setup Maintenance cleaning or device with automatic cleaning Remarks Requires extra energy Page 24 of 26 Code of practice solar water heaters and Legionella 23 04 2013 ANNEX D informative Good practice for solar assisted hot water systems Recommendation The winter time is the most Legionella vulnerable period of the year When the system is not in use during a significant part of this time the collector pump should be switched off Recommendation In all solar assisted hot water systems a mixing valve should be applied to prevent scald ing at the draw off points Preferably the mixing valve is located at the outflow from the auxiliary heater and set at 60 C 5 C If for special situations a thermostatic mixing valve applied to further reduce the outlet temperature e g 45 C is applied it should be incorporated into the draw off point or fit ted to it as close as possible Recommendation An instantaneous water heater as an auxiliary heater in a solar assisted hot water system should be able to tune the heating power to the inlet temperature Recommendation At least for solar storage tanks with a volume greater than
17. ion Part 1 General Specifications for installations inside buildings conveying water for human con sumption Part 2 Design Solar energy Vocabulary Thermal solar systems and components Factory made systems Part 1 General requirements Thermal solar systems and components Custom built systems Part 1 General requirements on the procedure for attesting the conformity of construction products in con tact with water intended for human consumption pursuant to Article 20 2 of Council Directive 89 106 EEC Anlagen f r Trinkwarmwasser in Geb uden Grundlagen und Anforderungen CEN TR 16355 Recommendations for prevention of Legionella growth in installations inside buildings conveying water for human consumption 2011 08 31 2 2 Other references 1 Report Legionella and solar water heaters April 2013 G van Amerongen vAConsult John v Lee Leegionella Ltd Jean Marc Suter Suter consulting 1 Also available in French under the title Installations d eau chaude sanitaire dans les b timents Bases g n rales et performances requises Page 7 of 26 Code of practice solar water heaters and Legionella 23 04 2013 3 Terms and definitions For the purpose of this document the following terms and definitions derived from EN 806 1 and EN ISO 9488 apply Hot water installation the complete installation from cold water supply to draw off points and all components in
18. k as follows 20 minutes at a temperature of 60 C or 10 minutes at 65 C or Page 16 of 26 Code of practice solar water heaters and Legionella 23 04 2013 5minutes at 70 C every day for high risk applications or every week for low and medium risk applications Confirmation of achieving these recommendations should be established by means of temper ature measurements in the storage tank or at its wall 6 3 Devices to detect malfunctioning 6 3 1 Malfunctioning of the collector loop The design considerations on managing the microbiological risk assume a correctly functioning solar heat generation and transfer As a consequence if malfunctioning occurs these as sumptions are no longer valid and the user should be warned of this The malfunctioning of the collector loop should be indicated to the user by means of a warning light situated in a location that is clearly visible to the user Stagnation in the collectors to pre vent system over temperature should not lead to the activation of the malfunction signal 6 3 2 Malfunctioning of the auxiliary heating part When an auxiliary heater is used to provide the essential function of thermal disinfection of the potable water there should be a clear alarm warning the user of any malfunctioning Moreover the user manual should include a description of how to act on this malfunction sig nal The auxiliary heater is malfunctioning when it is not functio
19. n B 3 for all solar only systems not fulfilling the recommendations of the Recommendations B 1 and B 2 The solar only system should be equipped with a device that either disinfects the storage tank every week or the outgoing potable water or prevents the growth of Legionella in the storage tank or heat exchanger in any other way Page 22 of 26 Code of practice solar water heaters and Legionella 23 04 2013 ANNEX C informative Non thermal disinfection techniques Several methods have been proposed as an alternative to thermal disinfection Disinfection by adding chemicals 1 Chlorine There are a variety of ways in which chlorine can be generated to treat water but the most common method used for supplementary treatment of water is the addition of sodium hypo chlorite NaOCl Chlorine can be added continuously at a low concentration 0 5 2 mg L to inhibit microbial growth or as a single shot high disinfecting concentration of 20 mg L for 2 to 3 hours Chlorination can be applied to all downstream parts of the system Disinfection is very dependent upon pH which should ideally be between pH 6 to 7 for effective disinfection and certainly no higher than pH 8 Chlorine also volatilises away with increasing temperature In some countries the limit for potable water is 0 5 mg L There may also be a need to obtain discharge consent depending upon national legislation and or to neutralise the biocidal activity before dis
20. ning according to the design assumptions Option 1 preferred The preferred way of communicating a malfunction is through the hot water itself When the auxiliary heater is malfunctioning the hot water temperature at the user s draw off point should be significantly reduced This could be accomplished through a controlled mixing valve that adds cold water or thru any other means In Figure 6 1 an example of such an installation scheme is given The mixing valve required by EN 12977 1 as scald protection is used to close the storage tank output as soon as the auxiliary heater is no longer able to maintain the recommended temperature for thermal disin fection This rapid reduction of the water temperature at the user s draw off point warns the user that the auxiliary heating is no longer able to ensure the protection against Legionella growth Warning the cold feed to the valve could become a deadleg vulnerable to legionella growth if it only feeds this safety valve To avoid this the cold feed to the valve should be as short as possible and taken from a pipe feeding a frequently used outlet such as a wash hand basin or toilet cistern Page 17 of 26 Code of practice solar water heaters and Legionella 23 04 2013 _ aa gt f lN 7 P T c Q Feed to cos SSS regularly i Ee we used outlet xs ao P p F SLS Solar part of heat storage Figure 6 1 Example of a device to detect insuffi
21. r collector loop Documentation a For systems that incorporate a means of cleaning the heat storage tank that stores po table water the user manual and the maintenance manual should include instructions on the methods and frequency of cleaning The user manual installation manual and maintenance manual should detail a proce dure to check the correct operation of the system The user manual should include a part dealing with recommendations to prevent mi crobiological risks including the growth of Legionella 7 In single family houses the level of maintenance of installations is usually poor It is expected that tanks will not be regularly inspected and cleaned Since small tanks are normally fitted in single family resi dences a recommendation to add an inspection hatch would be an ideal but in practice unlikely to be used However specific national regulations may require them Page 10 of 26 Code of practice solar water heaters and Legionella 23 04 2013 5 Warning signs and signalling When applicable warning signs or signals should be located so that the user or the service technician is clearly confronted with the warning For applications that are infrequently in spected by service personnel the warnings signs should be immediately obvious to the user Page 11 of 26 Code of practice solar water heaters and Legionella 23 04 2013 5 Recommendations applicable to solar assisted hot water systems
22. ractice solar water heaters and Legionella 23 04 2013 Recommendation R 3 Apply the following measures a b c Thermally disinfect the heat storage tank s according to the method described in para graph 6 2 Apply the recommendations of section 4 and follow the sampling procedure according to 6 4 Take appropriate measures when significant concentrations of Legionella are found Add a procedure to the maintenance manual describing a routine check to ensure the system is functioning correctly Recommendation R 4 a b Design the auxiliary storage tank volume to be larger than 1 2 of the daily design hot water demand and keep this tank at 60 C for the whole day Install a warning device to indicate any malfunctioning of the auxiliary heating part accord ing to subsection 6 3 2 In both the installer manual and the user manual state that exceptionally large water draw offs may result in a signal pointing to a malfunctioning of the auxiliary heating part 7 Under these conditions legionellae are effectively disinfected by the auxiliary heater Both disinfection duration and temperature are critical This recommendation exceeds the recommendation of 55 C in the CEN TR16355 Page 15 of 26 Code of practice solar water heaters and Legionella 23 04 2013 6 Methods 6 1 Intrinsic frequent thermal disinfection The following method gives recommendations for the design of the solar assisted ho
23. t water system to create optimal conditions for the frequent disinfection of the storage tank in the solar heating part Sizing of components The sizing of the components should be such that the maximum storage tank volume of the solar heating part follows the recommendations given in table 2 Storage tank design The storage tank design should be such that the bottom part of the storage tank can also be heated to at least 60 C When a heat exchanger is applied see section 4 paragraph 2b Table 2 Recommended solar storage tank volume per unitof collector aperture area I m Vsto Aco Recommended l m lt 120 for Legionella safe design for all applications 40 in North amp middle Europe under optimal collector orientation 55 in South Europe under optimal collector orientation or if the collector orientation is optimal BEN ae Vaaity and there is a Legionella warning a Notes latitude gt 45 azimuth SW SE and tilt angle between latitude 20 and latitude 5 latitude lt 45 Vto volume of solar dedicated part of storage tank Vaaily daily draw off volume explicit warning to the user of the system stating that the system becomes vulnerable to Legionella when seldom used 6 2 Forced thermal disinfection of a storage tank The following method gives recommendations for thermal disinfection of a storage tank Heat up the whole storage tan
24. tels military barracks Sport facilities indoor and outdoor pools Hospitals housing for elderly and disabled people prisons 5 2 Recommendations on system designs Recommendation R 1 The temperature in the auxiliary heat storage tank should be 2 55 C during the whole day or should be heated up to 60 C for one hour each day Recommendation R 2 Apply at least one of the following measures a Dimension the solar heating part in such a way that frequent thermal disinfection of the storage tank occurs according to the method described in 6 1 and apply a warning device to indicate possible malfunctioning of the collector loop according to 6 3 1 b Thermally disinfect the heat storage tank s according to the method described in para graph 6 2 c Apply one of the non thermal disinfection techniques listed in annex C t Although legionellae are present everywhere in aqueous environments only their introduction into the lung may be a potential health hazard Therefore apparatus and systems such as showers may present a risk through the aerosols that they create In addition the risk of getting sick increases if the person concerned has a weakened immune sys tem Although this is in accordance with the CEN TR 16355 4 shows that once a week should be sufficient Under these conditions the storage tank is frequently fully disinfected and the biofilm destroyed by solar heat Page 14 of 26 Code of p
25. ter system is applied e g collector orientation heat demand climatic region Prevention of Legionella growth requires measures to be applied to all devices whose function is to heat up the potable water Page 8 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Legionella the name epithet of a genus of bacteria that encompasses over 50 species including over 20 that have been associated with infection in man Legionella is analogous to Homo the genus to which humans belong legionella a bacterium of the genus Legionella analogous to a human legionellae the plural of legionella analogous to humans L pneumophila the name of a species for which pneumophila is the species specific epithet analogous to sa piens in Homo sapiens The most common cause of legionnaires disease decimal reduction time D the time taken to kill 90 of a population of bacteria or other organisms doubling time the time taken for a population of bacteria to double in number Also known as the generation time Page 9 of 26 Code of practice solar water heaters and Legionella 23 04 2013 4 Recommendations applicable to all solar water heaters All components containing potable water can potentially add to the risk from microbiological hazards In order to manage the risk from Legionella the following recommendations are given for the components of solar water heaters 1 Materials
26. uipment capable of dos ing single buildings has only recently been developed and still has limited availability Hospi tals receiving municipal water treated with monochloramine have been shown to be less likely to contain legionellae in their water systems and have a lower incidence of legionnaires dis ease Continuous dosing at up to 2 mg L could be applied and will penetrate to downstream parts of the installation Allowance exemption from authorities potable water and environment Extra installation parts dosing system Maintenance refills of dosing system 4 Other systems A variety of other chemicals have been proposed at potential methods for controlling legionel lae in water systems but there is too little information on their effectiveness at present to war rant their inclusion here Disinfection by applying devices 1 Terminal membrane filtration is a preventive measure with only local effects in the installation e g after the heat storage tank Allowance No information available Extra installation parts membrane setup Maintenance membrane cleaning and replacement Remarks Provided the filters are fitted correctly they can completely prevent the release of organisms from the draw off points but they do not reduce nor prevent colonisation They are particularly useful for short term emergency use 2 Treatment with UV light is a preventive measure with only local effects at the point of application e g a
27. vA Can su lf Suter Consulting B Code of practice Minimizing the risk of Legionella in solar assisted hot water systems Version Draft final Date 23 April 2013 Authors G van Amerongen vAConsult NL liaison officer for TC312 in TC164 John V Lee Leegionella Ltd UK Jean Marc Suter Suter Consulting CH deputy liaison officer for TC312 in TC164 This report was commissioned by the Solar Certification Fund and referenced under the acronym Legio2010 and the title Literature study on Legionella Code of practice solar water heaters and Legionella 23 04 2013 THE AUTHORS vA La nsult 7 Suter Consulting B eee te te me ages Anpa comes conmeneates Sanpa eiio unn Gerard A H van Amerongen vAConsult Fatswallerhof 22 NL 3069 PZ Rotterdam The Netherlands Phone 31 648 624 487 E mail vaconsult vaconsult net John V Lee Leegionella Ltd 46 Howletts Lane Ruislip HA4 7RS UK Phone 44 1895 674141 E mail JohnVLee leegionella co uk Jean Marc Suter Suter Consulting Multilingual written communication Aarstrasse 98 CH 3005 Berne Phone 41 31 311 49 42 E mail suter suterconsulting com Page 2 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Contents Frawo 525 2 iio cots esckid penceati ee dicate E eet ie BAe een Bete cee ee eee 4 MMFODUCHOMN a vera di ghanddvts ald aawsiededek aaee ane E uel waiieeddzia aes 5 T SCOPO Der ere re eia
28. vers a literature study on the subject and computer assisted mathematical simu lations Nevertheless it is noted that there is a need for additional research on the subject Page 4 of 26 Code of practice solar water heaters and Legionella 23 04 2013 Introduction TC164 WGz2 prepared a technical report entitled Recommendations for prevention of Le gionella growth in installations inside buildings conveying water for human consumption dated 2011 08 31 and referenced in this report as CEN TR 16355 CEN TR 16355 focuses on con ventional hot water systems and does not consider the applicability of its recommendations to solar water heaters This code of practice interprets CEN TR 16355 to adapt its recommenda tions to solar water heaters In the context of Legionella control the factors that need special consideration for solar water heaters are the use of storage tanks with frequently changing water temperatures in the range of 10 C to 80 C so that part of the tank and water is within the temperature range favourable to the growth of Legionella species the use of a storage tank that frequently and for long periods is at a temperature level above 60 C and as such disinfects the Legionella and biofilms within the tank the use of non solar heat sources that may thermally disinfect the hot water Solar only systems cannot guarantee a high enough hot water temperature at the draw off points as required by E
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