Difference between revisions of "Domestic Hot Water Systems"

From DIYWiki
Jump to navigation Jump to search
m (de spam)
Line 1: Line 1:
There is a wide and potentially bewildering variety of systems for supplying hot water in houses and flats ('''[[Domestic Hot Water]]''' or "'''DHW'''"). These include
+
[http://ashythro.info/library/html/morning-star/ morning star] [http://helmed.info/topic/avid-xpress/ avid xpress dv] [http://psisemiya.com/images/small/jody/ jody] [http://psisemiya.com/images/small/ragnarok/ ragnarok] [http://bloprofeldi.info/lib/acer-desktop.htm acer desktop] [http://ustall.org/web/nicholas-e.htm nicholas e berg] [http://psisemiya.com/images/small/jancker/ jancker] [http://helmed.info/topic/gerusalemme-shopping/ gerusalemme shopping] [http://bloprofeldi.info/lib/diffusori-per.htm diffusori per pc] [http://psisemiya.com/images/small/twice-mg/ twice 10mg 16 cps rp] [http://kinunia.cn/video-tiro.htm video tiro mancino amore impossibile] [http://bloprofeldi.info/lib/emittenti-televisive.htm emittenti televisive italiane] [http://helmed.info/topic/wireless-acces/ wireless acces point] [http://ashythro.info/library/html/samsung-kit/ samsung kit toner] [http://amohseni.info/img/styles/roll-deep/ roll deep] [http://helmed.info/topic/tennis-roland/ tennis roland garros] [http://davte.info/library/html/polo-jersey.htm polo jersey uomo] [http://bloprofeldi.info/lib/qui-fu.htm qui fu napoli] [http://psisemiya.com/images/small/olivetti-pg/ olivetti pg404] [http://ustall.org/web/alyssia-west.htm alyssia west baby got boobs] [http://amohseni.info/img/styles/temi-svolti/ temi svolti sull amicizia] [http://davte.info/library/html/f.htm f 884] [http://chaba.info/cavo-video/ cavo video rgb] [http://nobinters.org/automarket.htm automarket] [http://bloprofeldi.info/lib/diffusori-thx.htm diffusori thx] [http://chaba.info/kohler/ kohler] [http://amohseni.info/img/styles/trova-amici/ trova amici] [http://nobinters.org/download-tps.htm download tps echostar] [http://amohseni.info/img/styles/musica-romantica/ musica romantica cl] [http://saibso.org/venice.htm venice] [http://bloprofeldi.info/lib/stampanti-ink.htm stampanti ink- jet canon] [http://bloprofeldi.info/lib/lv-whirlpool.htm lv whirlpool] [http://psisemiya.com/images/small/ddddd/ ddddd] [http://kinunia.cn/tdk-lpcw.htm tdk lpcw] [http://chaba.info/avventura/ avventura] [http://ashythro.info/library/html/caricabatterie-doppio/ caricabatterie doppio] [http://chaba.info/nuova-smart/ nuova smart fortwo cabrio auto nuove] [http://bloprofeldi.info/lib/d-m.htm d m ambiente 10 9 1998 n 381] [http://ustall.org/web/haiducu.htm haiducu] [http://kinunia.cn/peja-sweet.htm peja sweet noise] [http://psisemiya.com/images/small/evangelion-the/ evangelion the end] [http://helmed.info/topic/athlon-/ athlon 64 fx51] [http://bloprofeldi.info/lib/calcarius.htm calcarius] [http://saibso.org/warren-g.htm warren g regulate] [http://ustall.org/web/sacca-passeggino.htm sacca passeggino] [http://davte.info/library/html/amyot-jacques.htm amyot, jacques] [http://chaba.info/north-solomons/ north solomons] [http://ustall.org/web/asus-socket.htm asus socket 939] [http://nobinters.org/laprovadelcuoco-rai.htm laprovadelcuoco rai it] [http://chaba.info/giorgia-nudi/ giorgia nudi] [http://bloprofeldi.info/lib/tutti-i.htm tutti i portatili] [http://chaba.info/wall/ wall] [http://amohseni.info/img/styles/autonoleggio-lecce/ autonoleggio lecce] [http://ashythro.info/library/html/battle-engine/ battle engine aquila plus 3 - trainer] [http://amohseni.info/img/styles/behringer-/ behringer - ultra-di pro di100] [http://helmed.info/topic/moto-cbr/ moto cbr 900] [http://kinunia.cn/offerta-albergo.htm offerta albergo vienna] [http://saibso.org/lcd-portatile.htm lcd portatile dvd] [http://psisemiya.com/images/small/lonely-regi/ lonely regi] [http://saibso.org/regali-natale.htm regali natale idea] [http://psisemiya.com/images/small/umano-non/ umano non umano] [http://psisemiya.com/images/small/oye-mi/ oye mi canto nore] [http://kinunia.cn/traduttore-spagnolo.htm traduttore spagnolo italiano] [http://ustall.org/web/plasma-high.htm plasma high definition] [http://bloprofeldi.info/lib/lettore-dvd.htm lettore dvd portatile tv] [http://saibso.org/joe-cuba.htm joe cuba] [http://amohseni.info/img/styles/divorzio/ divorzio] [http://psisemiya.com/images/small/nessuna-conferma/ nessuna conferma su out run 2] [http://kinunia.cn/frist-date.htm frist date] [http://davte.info/library/html/fiat-stilo.htm fiat stilo feel] [http://bloprofeldi.info/lib/frasi-d.htm frasi d amore in russo] [http://nobinters.org/pagine-bianche.htm pagine bianche avellino] [http://ustall.org/web/giannina-facio.htm giannina facio] [http://psisemiya.com/images/small/arte-scool/ arte scool] [http://saibso.org/facolta-di.htm facolta di psicologia messina] [http://amohseni.info/img/styles/cordoba-argentina/ cordoba argentina] [http://amohseni.info/img/styles/agenzia-matrimoniale/ agenzia matrimoniale napoli] [http://kinunia.cn/xerox-phaser.htm xerox phaser 8550 adp] [http://helmed.info/topic/osis/ osis] [http://chaba.info/versione-online/ versione online] [http://psisemiya.com/images/small/toner-nero/ toner nero ep-27] [http://saibso.org/navigatore-satellitare.htm navigatore satellitare acer] [http://kinunia.cn/celeron-fsb.htm celeron fsb 400mhz] [http://chaba.info/sex-cartoons/ sex cartoons] [http://bloprofeldi.info/lib/magnanina.htm magnanina] [http://ashythro.info/library/html/zucchero-live/ zucchero live at the albert] [http://helmed.info/topic/parata-d/ parata d eroi pellegrino] [http://chaba.info/tommy-by/ tommy by molto sugo] [http://helmed.info/topic/noleggio-lancia/ noleggio lancia thesis] [http://saibso.org/apple-ipod.htm apple ipod mini] [http://psisemiya.com/images/small/videogiochi-playstation/ videogiochi playstation 2 syberia] [http://psisemiya.com/images/small/magliette/ magliette] [http://helmed.info/topic/la-favorita/ la favorita di carlo ii] [http://kinunia.cn/goodbye.htm goodbye] [http://amohseni.info/img/styles/pasion-de/ pasion de] [http://helmed.info/topic/soderini/ soderini] [http://ashythro.info/library/html/cnet-usb/ cnet usb] [http://kinunia.cn/populorum-progressio.htm populorum progressio] [http://helmed.info/topic/tarim-yemen/ tarim yemen] [http://ustall.org/web/passat-tdi.htm passat tdi 130 cv highline 4 motion] [http://helmed.info/topic/fx-panasonic/ fx7 panasonic] [http://psisemiya.com/images/small/ala-val/ ala, val d-] [http://bloprofeldi.info/lib/carowinds-theme.htm carowinds theme park north carolina] [http://psisemiya.com/images/small/sex-car/ sex car] [http://chaba.info/pogledni/ pogledni] [http://helmed.info/topic/cuenta-conmigo/ cuenta conmigo] [http://ashythro.info/library/html/ariston-msz/ ariston msz 702 nf hb inox] [http://ustall.org/web/toro-news.htm toro news] [http://chaba.info/thong-tin/ thong tin ve may vi tinh] [http://psisemiya.com/images/small/specialista-tempi/ specialista tempi e metodi (regione lombardia - milano provincia)] [http://bloprofeldi.info/lib/lettore-mp.htm lettore mp3 radio 1g] [http://ustall.org/web/mamas-and.htm mamas and the papas california dreaming] [http://saibso.org/abaco.htm abaco] [http://helmed.info/topic/sito-vigili/ sito vigili del fuoco] [http://ashythro.info/library/html/hollywood-monster/ hollywood monster] [http://nobinters.org/feroza-daihatsu.htm feroza daihatsu] [http://amohseni.info/img/styles/rana/ rana] [http://bloprofeldi.info/lib/my-band.htm my band d12] [http://amohseni.info/img/styles/messina-hotel/ messina hotel] [http://helmed.info/topic/hotel-/ hotel 3 stelle napoli] [http://chaba.info/materialna/ materialna] [http://psisemiya.com/images/small/tom-jobim/ tom jobim] [http://kinunia.cn/energy-v.htm energy v2 4i] [http://chaba.info/godp/ godp] [http://saibso.org/gundam-armata.htm gundam armata] [http://kinunia.cn/televisori-plasma.htm televisori plasma] [http://nobinters.org/brembana.htm brembana] [http://ustall.org/web/fiorini-lando.htm fiorini lando] [http://psisemiya.com/images/small/kisssoft/ kisssoft] [http://saibso.org/balconcino-imbottito.htm balconcino imbottito] [http://amohseni.info/img/styles/fehrbellin/ fehrbellin] [http://saibso.org/business-opportunities.htm business opportunities] [http://psisemiya.com/images/small/vizietto/ vizietto] [http://psisemiya.com/images/small/yulieth/ yulieth] [http://nobinters.org/cavalcata-selvaggia.htm cavalcata selvaggia] [http://davte.info/library/html/si-estoy.htm si estoy facil] [http://chaba.info/zen-micro/ zen micro se] [http://helmed.info/topic/bcs/ bcs 333] [http://bloprofeldi.info/lib/autoradio-ingresso.htm autoradio ingresso] [http://helmed.info/topic/immagini-dei/ immagini dei simpson] [http://nobinters.org/numero-diciassette.htm numero diciassette] [http://helmed.info/topic/china-girl/ china girl] [http://psisemiya.com/images/small/comune-verona/ comune verona] [http://saibso.org/videos-veronique.htm videos veronique genest] [http://chaba.info/miele-w/ miele w 506] [http://psisemiya.com/images/small/bombermania/ bombermania] [http://helmed.info/topic/notizie-meteo/ notizie meteo sicilia] [http://chaba.info/bahama-shopping/ bahama shopping] [http://bloprofeldi.info/lib/guadagna-da.htm guadagna da casa] [http://davte.info/library/html/alexander-dumas.htm alexander dumas figlio] [http://amohseni.info/img/styles/sced-up/ sced up] [http://psisemiya.com/images/small/elio-germano/ elio germano] [http://psisemiya.com/images/small/tagawa/ tagawa] [http://nobinters.org/acer-.htm acer 1350 ram] [http://nobinters.org/video-chat.htm video chat italiane gratis] [http://davte.info/library/html/la-triglia.htm la triglia] [http://davte.info/library/html/softcam-keys.htm softcam keys] [http://nobinters.org/il-game.htm il game boy advance solo su ordinazione] [http://bloprofeldi.info/lib/idee-sui.htm idee sui regali di natale] [http://chaba.info/upskirt-video/ upskirt video gratis] [http://kinunia.cn/anyplace-anytime.htm anyplace anytime] [http://ashythro.info/library/html/toyota-f/ toyota f1] [http://kinunia.cn/spamming.htm spamming] [http://ustall.org/web/www-filipinaheart.htm www filipinaheart com] [http://chaba.info/book-ragazze/ book ragazze per foto nudo] [http://helmed.info/topic/student-microsoft/ student microsoft] [http://psisemiya.com/images/small/arredamento-estetica/ arredamento estetica] [http://bloprofeldi.info/lib/easy.htm easy] [http://psisemiya.com/images/small/hdd-recorder/ hdd recorder panasonic dvd] [http://chaba.info/teenme-com/ teenme com] [http://bloprofeldi.info/lib/blue-a.htm blue a chi mi dice from festivalbar] [http://davte.info/library/html/nforce-.htm nforce 4 ultra] [http://ustall.org/web/lampeggiatore-sb.htm lampeggiatore sb 800] [http://amohseni.info/img/styles/pirandello-enrico/ pirandello enrico vi] [http://chaba.info/capitali/ capitali] [http://helmed.info/topic/lsa-vuelta/ lsa vuelta] [http://amohseni.info/img/styles/rivoluzione-industriale/ rivoluzione industriale] [http://helmed.info/topic/samba-me/ samba me] [http://saibso.org/vernice.htm vernice] [http://bloprofeldi.info/lib/rendiconto-parigino.htm rendiconto parigino] [http://kinunia.cn/il-sindacato.htm il sindacato di chicago] [http://chaba.info/classifica-hit/ classifica hit] [http://psisemiya.com/images/small/aziende-guinea/ aziende guinea bissau] [http://chaba.info/www-pianetascuola/ www pianetascuola it] [http://nobinters.org/hotmeil.htm hotmeil] [http://amohseni.info/img/styles/vetro-mattone/ vetro mattone] [http://helmed.info/topic/felpe-uomo/ felpe uomo cappuccio] [http://chaba.info/lesbiche-gay/ lesbiche gay] [http://chaba.info/zyxel-h/ zyxel 650h] [http://kinunia.cn/polti.htm polti 4500] [http://ashythro.info/library/html/zecchinodoro/ zecchinodoro] [http://ustall.org/web/strghe.htm strghe] [http://bloprofeldi.info/lib/filmato-di.htm filmato di un rapporto sessuale] [http://ustall.org/web/barcellona-queen.htm barcellona queen] [http://amohseni.info/img/styles/attila-flagello/ attila flagello dio] [http://saibso.org/garbahaarey.htm garbahaarey] [http://ustall.org/web/revista-trip.htm revista trip] [http://helmed.info/topic/tfy/ tfy] [http://kinunia.cn/taglio-precisione.htm taglio precisione] [http://amohseni.info/img/styles/lettore-schede/ lettore schede xd] There is a wide and potentially bewildering variety of systems for supplying hot water in houses and flats ('''[[Domestic Hot Water]]''' or "'''DHW'''"). These include
 
* Conventional systems with a large tank in the attic and a hot water cylinder
 
* Conventional systems with a large tank in the attic and a hot water cylinder
 
* Combi Boilers
 
* Combi Boilers
Line 8: Line 8:
 
and more ....
 
and more ....
  
This document aims to explain the principles underlying the different types and why one would choose one rather than another. In particular the various types of mains pressure systems - [[Unvented DHW|'''unvented''']] and [[Thermal store|'''thermal stores/heat banks''']] - becoming increasingly common in the UK are discussed, as are solar and other renewable systems.
+
This document aims to explain the principles underlying the different types an
 
 
This article describes the main features of DHW systems and explains terms used in describing such systems. Further articles will give more details on particular varieties of system, including some hybrid systems combining elements of the basic types discussed here, discussion of some commercial and other systems available, and links to suppliers' web sites and other resources.
 
 
 
== Main types of DHW system ==
 
 
 
The main differences between types of DHW systems are:
 
* '''Instantaneously heated''' e.g. [[Combination Boilers|combi boilers]], multipoint ('Ascot'-type) instantaneous gas water heaters, instantaneous electric water heaters
 
 
 
''versus''
 
* '''Stored heat''' e.g. systems with some sort of hot water cylinder
 
 
 
and
 
* '''Mains pressure water''' e.g. [[Combination Boilers|combi boilers]], unvented ('Megaflow' type) cylinders
 
 
 
''versus''
 
* '''Low pressure with stored water''' e.g. conventional: tank in attic and hot water cylinder in airing cupboard
 
 
 
The pros and cons of these systems are:
 
 
{| border="1" cellpadding="20" cellspacing="0"
 
!
 
!PRO
 
!CON
 
|-
 
! valign="top"| Instantaneous
 
| valign="top"|
 
* Continual supply of hot water.
 
| valign="top"|
 
* Rate of supply limited by fuel supply/consumption. No backup when heater (e.g. combi) fails.
 
|-
 
! valign="top"| Stored heat
 
| valign="top"|
 
* Potentially very high rate of supply of hot water.
 
* Can accomodate backup heating (e.g. electric immersion for gas boiler) and multiple heat sources (e.g. solar + gas).
 
| valign="top"|
 
* Supply runs cold when stored heat exhausted: takes time to re-heat.
 
* Heat lost from store while not in use.
 
|-
 
<!-- we want a blank row to separate the half of the table above from that below -- there should be a neater way but this seems to work -->
 
!
 
!
 
!
 
|-
 
! valign="top"| Mains pressure
 
| valign="top"|
 
* 'Dry loft': no need for tank in attic.
 
* Good pressure for showers & monobloc mixer taps even in attic spaces.
 
| valign="top"|
 
* Dependant on pressure and continuity of mains water supply.
 
|-
 
! valign="top"| Low pressure stored water
 
| valign="top"|
 
* Independant of fluctuations in mains water pressure and temporary loss of supply.
 
| valign="top"|
 
* Relatively low supply pressure especially at top of building.
 
* Requires large storage tank in attic or high in building.
 
* Pumps usually required for showers and some types of taps.
 
|}
 
 
 
'''Instantaneously heated''' systems are generally also '''mains pressure''' systems. The familiar system with a tank in the attic and a cylinder in the airing cupboard is '''stored heat''' and '''low pressure stored water'''. There are also two main types of stored heat mains pressure systems: '''Unvented''' and '''Thermal Stores & Heat Banks'''.
 
 
 
Combining these factors we have:
 
{| border="1" cellpadding="20" cellspacing="0"
 
!
 
!Instantaneous
 
!Stored Heat
 
|-
 
! valign="top"| Mains pressure
 
| valign="top"|
 
* Combi boilers
 
* "Ascot"-type water heaters ("geysers")
 
* Electrically heated showers
 
| valign="top"|
 
* Unvented (e.g. "Megaflow") cylinders
 
* Thermal Stores & Heat Banks.
 
|-
 
! valign="top"| Low pressure stored water
 
| valign="top"|
 
''Not generally found in DHW systems''
 
| valign="top"|
 
* Conventional system: cold water storage tank in attic and hot water cylinder in airing cupboard, usually heated by a gas boiler with electric immersion heater for backup
 
|}
 
 
 
 
 
----
 
 
 
== Mains pressure stored heat systems: Unvented versus Thermal Store/Heat Bank ==
 
 
 
Although they serve the same purpose - to provide a copious supply of hot water at mains pressure from a storage tank - unvented systems and thermal stores work in radically different ways.
 
 
 
=== Unvented systems ===
 
 
 
Like a conventional hot water cylinder fed from a tank in the roof, an unvented cylinder contains hot water (heated by a boiler or immersion heater) which directly supplies the hot taps. However the water in an unvented cylinder comes directly from the cold water main and is at (nearly) mains pressure. Obviously the cyclinder has to be physically stronger to withstand the higher pressure of the mains water, but also various other safety devices have to be incorporated into such systems.
 
 
 
[[Unvented DHW|More on unvented systems]].
 
 
 
=== Thermal stores and heat banks ===
 
 
 
In these systems a container of water under low pressure is heated by the boiler or immersion heater etc. Mains pressure cold water passes through a heat exchanger to be heated by water from the store to supply the taps etc. There are various different configurations of thermal stores and heat banks.
 
[[Thermal store|More on thermal stores and heat banks]]
 
 
 
<!-- The section following is placed in a box (1 row 1 column table) to highlight it and separate it from the rest of the text -->
 
<center>
 
{| style="width:85%" border="1" cellpadding="2"
 
|-
 
|
 
== Stratification ==
 
 
 
In a vessel containing water at different temperatures the hotter water will tend to accumulate at the top with progessively cooler water further down. This phenomenon is called stratification and is generally desirable in DHW systems. In the relatively tall and narrow cylinders used in DHW systems this stratification is more pronounced, allowing a wide range of temperatures from top to bottom e.g. 60C nearer the top and 10C lower down.
 
|}
 
</center>
 
<!-- Do not remove the |} and </center> markup above unless you remove the corresponding markup before the section head -->
 
 
 
== Direct and Indirect systems ==
 
 
 
Conventional gravity-fed cylinders, thermal stores and heat banks have two different arrangements for heating the water contained in them.
 
 
 
* In '''Direct''' systems the water in the cylinder is heated directly, either by an electric imersion heater in the cylinder or by the water being circulated around a boiler. This was a common arrangement with back-boilers behind open fireplaces and ranges such as Agas and Rayburns, but is not generally used with central heating boilers.
 
 
 
* In '''Indirect''' systems the cylinder has a heat exchanger coil to transfer heat from the primary heat source (e.g. boiler) to the water in the cylinder. This keeps the water in the boiler separate from the water in the cylinder, allowing the water in the boiler and central heating radiators to be treated with chemicals and kept free of dissolved oxygen to prevent corrosion of iron or steel radiators and boilers. All unvented systems are indirect.
 
 
 
----
 
 
 
{| border="1" cellpadding="20" cellspacing="0"
 
!Direct
 
!Indirect
 
|-
 
|[[Image:DHW_direct_cylinder.gif]]
 
|[[Image:DHW_indirect_cylinder.gif]]
 
|}
 
 
 
== Primary and Secondary ==
 
 
 
In indirect systems there are two separate bodies of water. '''Primary''' water circulates around the primary heat source (e.g.  boiler) and transfers heat (via the heat exchanger coil in the '''Indirect''' diagram above) to the '''Secondary''' water (in the body of the cylinder, above) which supplies DHW. In some systems there are more than two separate bodies of water but there is no clearly agreed nomenclature for such systems (e.g. 'tertiary' water).
 
 
 
<!-- The section following is placed in a box (1 row 1 column table) to highlight it and separate it from the rest of the text -->
 
<center>
 
{| style="width:85%" border="1" cellpadding="2"
 
|-
 
|
 
=== Primatic cylinders ===
 
A type of system which is still sometimes found in older installations uses a cylinder (usually known as a "'''Primatic'''") in which the primary (boiler) water and secondary (DHW) water are supplied from the same (DHW) tank but has an arrangement within the cylinder which uses trapped air to keep the two bodies of water separate during operation. These types of cylinder have poor heat transfer from primary to secondary water, and must not be used with corrosion inhibitor or other chemicals in the primary water. They are not used for new DHW systems.
 
|}
 
</center>
 
<!-- Do not remove the |} and </center> markup above unless you remove the corresponding markup before the section head -->
 
 
 
== Recovery ==
 
'''(Re-heating performance)'''
 
 
 
In '''Direct''' systems hot water from a boiler can circulate directly through the cylinder so the rate at which the cylinder water heats up is limited only by the heat output of the boiler. In '''Indirect''' systems the rate of heating is usually limited by the rate of transfer across the heat exchanger coil. The time taken to heat (or re-heat) the cylinder is its recovery time. Poor recovery can result in the boiler '''cycling''' - switching off and on instead of running continously - as well as slow re-heating of  the water. The Building Regulations ''[citation needed]'' covering cylinders now call for better performance from modern cylinders than was acceptable from older designs. For example for a common size of cylinder (450mm diameter x 900mm height) a standard size coil will have a surface area of about 0.6 square metres and will heat the water from 10C to 60C in about 25 minutes (with a primary flow of about 15 litres per minute at 82C). A fast-recovery cylinder of the same size will have approximately twice the surface area of coil and a recovery time of about 15 minutes (with 18 litres/minute primary flow).
 
 
 
==See Also==
 
*[[Unvented DHW|Unvented DHW systems]]
 
*[[Thermal store|Thermal stores and heat banks]]
 
 
 
 
 
[[Category: Plumbing]]
 
[[Category: Heating]]
 
[[Category: Domestic Hot Water]]
 

Revision as of 04:34, 17 August 2007

morning star avid xpress dv jody ragnarok acer desktop nicholas e berg jancker gerusalemme shopping diffusori per pc twice 10mg 16 cps rp video tiro mancino amore impossibile emittenti televisive italiane wireless acces point samsung kit toner roll deep tennis roland garros polo jersey uomo qui fu napoli olivetti pg404 alyssia west baby got boobs temi svolti sull amicizia f 884 cavo video rgb automarket diffusori thx kohler trova amici download tps echostar musica romantica cl venice stampanti ink- jet canon lv whirlpool ddddd tdk lpcw avventura caricabatterie doppio nuova smart fortwo cabrio auto nuove d m ambiente 10 9 1998 n 381 haiducu peja sweet noise evangelion the end athlon 64 fx51 calcarius warren g regulate sacca passeggino amyot, jacques north solomons asus socket 939 laprovadelcuoco rai it giorgia nudi tutti i portatili wall autonoleggio lecce battle engine aquila plus 3 - trainer behringer - ultra-di pro di100 moto cbr 900 offerta albergo vienna lcd portatile dvd lonely regi regali natale idea umano non umano oye mi canto nore traduttore spagnolo italiano plasma high definition lettore dvd portatile tv joe cuba divorzio nessuna conferma su out run 2 frist date fiat stilo feel frasi d amore in russo pagine bianche avellino giannina facio arte scool facolta di psicologia messina cordoba argentina agenzia matrimoniale napoli xerox phaser 8550 adp osis versione online toner nero ep-27 navigatore satellitare acer celeron fsb 400mhz sex cartoons magnanina zucchero live at the albert parata d eroi pellegrino tommy by molto sugo noleggio lancia thesis apple ipod mini videogiochi playstation 2 syberia magliette la favorita di carlo ii goodbye pasion de soderini cnet usb populorum progressio tarim yemen passat tdi 130 cv highline 4 motion fx7 panasonic ala, val d- carowinds theme park north carolina sex car pogledni cuenta conmigo ariston msz 702 nf hb inox toro news thong tin ve may vi tinh specialista tempi e metodi (regione lombardia - milano provincia) lettore mp3 radio 1g mamas and the papas california dreaming abaco sito vigili del fuoco hollywood monster feroza daihatsu rana my band d12 messina hotel hotel 3 stelle napoli materialna tom jobim energy v2 4i godp gundam armata televisori plasma brembana fiorini lando kisssoft balconcino imbottito fehrbellin business opportunities vizietto yulieth cavalcata selvaggia si estoy facil zen micro se bcs 333 autoradio ingresso immagini dei simpson numero diciassette china girl comune verona videos veronique genest miele w 506 bombermania notizie meteo sicilia bahama shopping guadagna da casa alexander dumas figlio sced up elio germano tagawa acer 1350 ram video chat italiane gratis la triglia softcam keys il game boy advance solo su ordinazione idee sui regali di natale upskirt video gratis anyplace anytime toyota f1 spamming www filipinaheart com book ragazze per foto nudo student microsoft arredamento estetica easy hdd recorder panasonic dvd teenme com blue a chi mi dice from festivalbar nforce 4 ultra lampeggiatore sb 800 pirandello enrico vi capitali lsa vuelta rivoluzione industriale samba me vernice rendiconto parigino il sindacato di chicago classifica hit aziende guinea bissau www pianetascuola it hotmeil vetro mattone felpe uomo cappuccio lesbiche gay zyxel 650h polti 4500 zecchinodoro strghe filmato di un rapporto sessuale barcellona queen attila flagello dio garbahaarey revista trip tfy taglio precisione lettore schede xd There is a wide and potentially bewildering variety of systems for supplying hot water in houses and flats (Domestic Hot Water or "DHW"). These include

  • Conventional systems with a large tank in the attic and a hot water cylinder
  • Combi Boilers
  • Unvented (e.g. Megaflo)
  • Thermal Stores or Heat Banks
  • Solar Hot Water systems
  • Gas multipoint heaters (like old Ascot types)

and more ....

This document aims to explain the principles underlying the different types an