Difference between revisions of "Domestic Hot Water Systems"

From DIYWiki
Jump to navigation Jump to search
(rv 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://lady-mosquito.ifrance.com/web/hangzhou-wan/ hangzhou wan] [http://me4tateljnitsa.ifrance.com/data/domanda-di/ domanda di insegnamento] [http://bagrec.ifrance.com/lib/lbp.htm lbp 5200] [http://gmkamm.ifrance.com/view/new/legislazione-amministrativa.htm legislazione amministrativa] [http://me4tateljnitsa.ifrance.com/data/msi-megabook/ msi megabook s260] [http://orbzine.ifrance.com/images/small/les-amants.htm les amants de mogador] [http://sherryfraser03.ifrance.com/web/profumi-uomo/ profumi uomo giorgio armani] [http://epireial-h.ifrance.com/topic/suor-piera.htm suor piera cori] [http://cannotspell.ifrance.com/description/lib/mazziniano/ mazziniano] [http://la-seras.ifrance.com/library/html/sec.htm sec2] [http://fishing-gro.ifrance.com/html/asus-palmare/ asus palmare mypal a620bt] [http://fishing-gro.ifrance.com/html/polti-lecoaspira/ polti lecoaspira 710 kit] [http://butanexlove.ifrance.com/lib/harr-potter.htm harr potter] [http://heyclassylady.ifrance.com/html/aqua-energiser.htm aqua energiser] [http://stasiia.ifrance.com/img/styles/big-balls/ big balls] [http://fishing-gro.ifrance.com/html/konica-minolta/ konica minolta  dimage z5] [http://orbzine.ifrance.com/images/small/ati-fire.htm ati fire gl] [http://gmkamm.ifrance.com/view/new/riassunto-generale.htm riassunto generale promessi sposi] [http://gmkamm.ifrance.com/view/new/assicurazione-merano.htm assicurazione merano] [http://cannotspell.ifrance.com/description/lib/fhm-com/ fhm com ph] [http://cannotspell.ifrance.com/description/lib/flag-to/ flag to flag] [http://last-shadow.ifrance.com/text/directory/brick-champion/ brick champion chip] [http://lauashbu.ifrance.com/lib/stivali-per/ stivali per uomo] [http://heyclassylady.ifrance.com/html/radio-di.htm radio di r wiliams] [http://ryandrablya.ifrance.com/lib/divx-hd.htm divx hd] [http://heyclassylady.ifrance.com/html/canvass.htm canvass] [http://zonkismusik.ifrance.com/img/styles/videos-de.htm videos de sexo virtual] [http://bagrec.ifrance.com/lib/hamlet-zelig.htm hamlet zelig music] [http://zonkismusik.ifrance.com/img/styles/java-com.htm java com] [http://cannotspell.ifrance.com/description/lib/viaggi-cecoslovacchia/ viaggi cecoslovacchia] [http://rielethuil.ifrance.com/description/lib/portavasi.htm portavasi] [http://me4tateljnitsa.ifrance.com/data/imo-fiume/ imo (fiume)] [http://gmkamm.ifrance.com/view/new/disoccupazione.htm disoccupazione] [http://lauashbu.ifrance.com/lib/yu-gi/ yu gi oh sito ufficiale] [http://butanexlove.ifrance.com/lib/tetra-pak.htm tetra pak] [http://zonkismusik.ifrance.com/img/styles/www-sepel.htm www sepel com] [http://last-shadow.ifrance.com/text/directory/www-easyjet/ www easyjet it] [http://epireial-h.ifrance.com/topic/bagnetto-bimbo.htm bagnetto bimbo] [http://rielethuil.ifrance.com/description/lib/ww-google.htm ww google cl] [http://bagrec.ifrance.com/lib/jupiter-brevi.htm jupiter brevi] [http://cannotspell.ifrance.com/description/lib/deb-e/ deb e dave] [http://zonkismusik.ifrance.com/img/styles/porno-gratis.htm porno gratis en la red] [http://pegasik.ifrance.com/html/gore-vidal/ gore vidal] [http://sherryfraser03.ifrance.com/web/wiso-dvd/ wiso dvd recorder] [http://ryandrablya.ifrance.com/lib/microsoft-exchange.htm microsoft exchange 2003] [http://cannotspell.ifrance.com/description/lib/rivali/ rivali] [http://gmkamm.ifrance.com/view/new/turtles.htm turtles 2] [http://lauashbu.ifrance.com/lib/galactic-teddy/ galactic teddy] [http://rielethuil.ifrance.com/description/lib/vidoe.htm vidoe] [http://uo-ination.ifrance.com/lib/rete-aziendale/ rete aziendale] [http://uo-ination.ifrance.com/lib/telefono-per/ telefono per pc] [http://heyclassylady.ifrance.com/html/www-alessandro.htm www alessandro it] [http://bagrec.ifrance.com/lib/rassegna-stampa.htm rassegna stampa] [http://zonkismusik.ifrance.com/img/styles/konus.htm konus 114] [http://me4tateljnitsa.ifrance.com/data/dragosta-din/ dragosta din tei ozone] [http://la-seras.ifrance.com/library/html/fiat-voluntas.htm fiat voluntas dei] [http://fishing-gro.ifrance.com/html/rosa-balistreri/ rosa balistreri] [http://epireial-h.ifrance.com/topic/look-for.htm look for book] [http://uo-ination.ifrance.com/lib/spiaggia-santa/ spiaggia santa maria havana] [http://gmkamm.ifrance.com/view/new/elettronica-transistor.htm elettronica transistor] [http://epireial-h.ifrance.com/topic/colonia-estiva.htm colonia estiva] [http://pegasik.ifrance.com/html/acer-notebook/ acer notebook aspire 1692wlmi] [http://orbzine.ifrance.com/images/small/peter-tosh.htm peter tosh] [http://pegasik.ifrance.com/html/piedi-femminili/ piedi femminili] [http://rielethuil.ifrance.com/description/lib/pagina.htm pagina 21] [http://sherryfraser03.ifrance.com/web/cappotto-cani/ cappotto cani] [http://fishing-gro.ifrance.com/html/extra-large/ extra large] [http://lauashbu.ifrance.com/lib/lord-byron/ lord byron] [http://me4tateljnitsa.ifrance.com/data/sandali-miu/ sandali miu miu] [http://pegasik.ifrance.com/html/neovo-f/ neovo f 419] [http://fishing-gro.ifrance.com/html/gelfo/ gelfo] [http://bagrec.ifrance.com/lib/roveredo-di.htm roveredo di gu] [http://la-seras.ifrance.com/library/html/bomba.htm bomba] [http://fishing-gro.ifrance.com/html/in-italiano/ in italiano] [http://zonkismusik.ifrance.com/img/styles/sfondi-per.htm sfondi per telefonino] [http://me4tateljnitsa.ifrance.com/data/video-degli/ video degli evanescence] [http://la-seras.ifrance.com/library/html/telefono-registratore.htm telefono registratore] [http://stasiia.ifrance.com/img/styles/incentivi-statali/ incentivi statali auto metano] [http://rielethuil.ifrance.com/description/lib/foto-giovanna.htm foto giovanna grande fratello 6] [http://ryandrablya.ifrance.com/lib/poliuretan.htm poliuretan] [http://gmkamm.ifrance.com/view/new/the-waves.htm the waves of love] [http://last-shadow.ifrance.com/text/directory/lupo-tdi/ lupo tdi] [http://bagrec.ifrance.com/lib/aculaser-c.htm aculaser c1100 a4 color] [http://epireial-h.ifrance.com/topic/zuchero-baila.htm zuchero baila morena] [http://uo-ination.ifrance.com/lib/volvo-/ volvo 850 sw t5] [http://bagrec.ifrance.com/lib/tesina-italiano.htm tesina italiano] [http://pegasik.ifrance.com/html/lyell-sir/ lyell sir charles] [http://cannotspell.ifrance.com/description/lib/afs-nikkor/ afs nikkor 1870mm f 3 54 5 g ed] [http://cannotspell.ifrance.com/description/lib/volkswagen-/ volkswagen          vento 19 tdi  gl] [http://epireial-h.ifrance.com/topic/website-marketing.htm website marketing strategy] [http://me4tateljnitsa.ifrance.com/data/sesso-be/ sesso be] [http://cannotspell.ifrance.com/description/lib/san-francesco/ san francesco d assisi santo] [http://gmkamm.ifrance.com/view/new/scheda-video.htm scheda video pci 6600] [http://cannotspell.ifrance.com/description/lib/ddr-/ ddr 400 512 mb] [http://bagrec.ifrance.com/lib/mp-pro.htm mp3 pro] [http://pegasik.ifrance.com/html/automobile-usata/ automobile usata vendita] [http://uo-ination.ifrance.com/lib/comune-di/ comune di alife] [http://gmkamm.ifrance.com/view/new/siemens-amilo.htm siemens amilo v7010] [http://stasiia.ifrance.com/img/styles/simac-gelatiere/ simac gelatiere] [http://lady-mosquito.ifrance.com/web/batterie-musicali/ batterie musicali] [http://bagrec.ifrance.com/lib/macro-foto.htm macro foto fotocamere digitali] [http://lauashbu.ifrance.com/lib/los-canos/ los canos] [http://cannotspell.ifrance.com/description/lib/hotels-lago/ hotels lago di garda] [http://pegasik.ifrance.com/html/hard-disc/ hard disc portatile] [http://orbzine.ifrance.com/images/small/acer-pda.htm acer pda n30 gps] [http://cannotspell.ifrance.com/description/lib/spyware-stormer/ spyware stormer] [http://orbzine.ifrance.com/images/small/free-paswords.htm free paswords] [http://pegasik.ifrance.com/html/trasmissioni-meccaniche/ trasmissioni meccaniche] [http://cannotspell.ifrance.com/description/lib/x-gon/ x gon give it to ya] [http://la-seras.ifrance.com/library/html/paese-oga.htm paese oga] [http://sherryfraser03.ifrance.com/web/roma-corfu/ roma corfu biglietti aerei] [http://gmkamm.ifrance.com/view/new/soluzione-call.htm soluzione call center] [http://rielethuil.ifrance.com/description/lib/gradino-step.htm gradino step] [http://epireial-h.ifrance.com/topic/stefano-scarampella.htm stefano scarampella] [http://rielethuil.ifrance.com/description/lib/ricevitore-digitale.htm ricevitore digitale terrestre strong] [http://zonkismusik.ifrance.com/img/styles/passaggio-da.htm passaggio da pubblico a privato] [http://zonkismusik.ifrance.com/img/styles/audi-a.htm audi a3 32] [http://rielethuil.ifrance.com/description/lib/coppie-porche.htm coppie porche] [http://zonkismusik.ifrance.com/img/styles/nokia-.htm nokia 6600 cavo] [http://epireial-h.ifrance.com/topic/hajjah.htm hajjah] [http://lauashbu.ifrance.com/lib/oro-pisa/ oro pisa] [http://me4tateljnitsa.ifrance.com/data/firenze-mangiare/ firenze mangiare bere] [http://me4tateljnitsa.ifrance.com/data/www-sexool/ www sexool com] [http://rielethuil.ifrance.com/description/lib/nephrolepis.htm nephrolepis] [http://last-shadow.ifrance.com/text/directory/phentermine-diet/ phentermine diet pill] [http://rielethuil.ifrance.com/description/lib/giochi-da.htm giochi da tavolo sexy] [http://zonkismusik.ifrance.com/img/styles/martin-pierre.htm martin pierre] [http://heyclassylady.ifrance.com/html/it-s.htm it s so be quiet] [http://uo-ination.ifrance.com/lib/pescara/ pescara] [http://bagrec.ifrance.com/lib/samsung-tvc.htm samsung tvc] [http://pegasik.ifrance.com/html/de-geer/ de geer gerard jakob] [http://sherryfraser03.ifrance.com/web/diplo/ diplo] [http://uo-ination.ifrance.com/lib/quick-player/ quick player] [http://rielethuil.ifrance.com/description/lib/oakley-fives.htm oakley fives 2 0] [http://heyclassylady.ifrance.com/html/bf-srl.htm bf srl bolzano] [http://bagrec.ifrance.com/lib/software-email.htm software email marketing] [http://cannotspell.ifrance.com/description/lib/holding-out/ holding out for hero] [http://rielethuil.ifrance.com/description/lib/perreo-en.htm perreo en vivo] [http://gmkamm.ifrance.com/view/new/stokke-letto.htm stokke letto] [http://pegasik.ifrance.com/html/memory-stick/ memory stick 1gb sony psp] [http://ryandrablya.ifrance.com/lib/whirlpool-forni.htm whirlpool forni a microonde] [http://butanexlove.ifrance.com/lib/martinica.htm martinica] [http://lauashbu.ifrance.com/lib/buap/ buap] [http://cannotspell.ifrance.com/description/lib/lultima-rapina/ lultima rapina] [http://sherryfraser03.ifrance.com/web/schiava-e/ schiava e signora] [http://sherryfraser03.ifrance.com/web/b-/ b  c srl] [http://me4tateljnitsa.ifrance.com/data/palawan/ palawan] [http://la-seras.ifrance.com/library/html/modal-shorts.htm modal shorts] [http://sherryfraser03.ifrance.com/web/in-amore/ in amore] [http://fishing-gro.ifrance.com/html/legen-of/ legen of zelda] [http://gmkamm.ifrance.com/view/new/il-tempio.htm il tempio greco] [http://butanexlove.ifrance.com/lib/euro-convertitore.htm euro convertitore] [http://fishing-gro.ifrance.com/html/manele-mp/ manele mp3] [http://ryandrablya.ifrance.com/lib/driver-per.htm driver per voodoo 3] [http://pegasik.ifrance.com/html/intel-pentium/ intel pentium 4 2 8 ghz] [http://sherryfraser03.ifrance.com/web/mx/ mx 3100] [http://pegasik.ifrance.com/html/tony-britten/ tony britten] [http://me4tateljnitsa.ifrance.com/data/recetas/ recetas] [http://sherryfraser03.ifrance.com/web/smart-media/ smart media] [http://me4tateljnitsa.ifrance.com/data/curcio/ curcio] [http://lauashbu.ifrance.com/lib/alimentatore-asus/ alimentatore asus a730] [http://me4tateljnitsa.ifrance.com/data/harlem-notturno/ harlem notturno] [http://sherryfraser03.ifrance.com/web/nokia/ nokia3310] [http://lauashbu.ifrance.com/lib/europe-musica/ europe musica cd] [http://orbzine.ifrance.com/images/small/frittelle-crema.htm frittelle crema] [http://fishing-gro.ifrance.com/html/latina-oggi/ latina oggi] [http://sherryfraser03.ifrance.com/web/toner-canon/ toner canon lbp810] [http://rielethuil.ifrance.com/description/lib/notre-dame.htm notre dame de paris italian version] [http://zonkismusik.ifrance.com/img/styles/sofia-vergara.htm sofia vergara nua] [http://lauashbu.ifrance.com/lib/xxx-black/ xxx black women movie vree] [http://la-seras.ifrance.com/library/html/michele-ranieri.htm michele ranieri snc] [http://orbzine.ifrance.com/images/small/traduzione-california.htm traduzione california phantom] [http://heyclassylady.ifrance.com/html/concerto-air.htm concerto air talkie roma] [http://butanexlove.ifrance.com/lib/dragostea-din.htm dragostea din tei da scaricare] [http://cannotspell.ifrance.com/description/lib/marat-safin/ marat safin] [http://bagrec.ifrance.com/lib/etichetta-alimentari.htm etichetta alimentari] [http://orbzine.ifrance.com/images/small/rotting-com.htm rotting com] [http://fishing-gro.ifrance.com/html/no-milk/ no milk to day] [http://fishing-gro.ifrance.com/html/suncanom/ suncanom] [http://zonkismusik.ifrance.com/img/styles/ferro-mid.htm ferro mid] [http://lady-mosquito.ifrance.com/web/congelatore-electrolux/ congelatore electrolux] [http://bagrec.ifrance.com/lib/lettori-dvd.htm lettori dvd thomson] [http://rielethuil.ifrance.com/description/lib/cavalcata.htm cavalcata] [http://me4tateljnitsa.ifrance.com/data/stay-whit/ stay whit me] [http://la-seras.ifrance.com/library/html/puffetta.htm puffetta] [http://epireial-h.ifrance.com/topic/karaoke-professionale.htm karaoke professionale] [http://heyclassylady.ifrance.com/html/garway-ltd.htm garway ltd] [http://zonkismusik.ifrance.com/img/styles/juliana-do.htm juliana do bb nua] [http://pegasik.ifrance.com/html/linksys-psus/ linksys psus4] [http://epireial-h.ifrance.com/topic/diario-di.htm diario di un italiano] [http://ryandrablya.ifrance.com/lib/mini-lavatrice.htm mini lavatrice automatica] [http://fishing-gro.ifrance.com/html/risultati-concorso/ risultati concorso carriera prefettizia] [http://zonkismusik.ifrance.com/img/styles/outlet-torino.htm outlet torino] [http://cannotspell.ifrance.com/description/lib/corse-con/ corse con le macchinine a 21 macchine] [http://ryandrablya.ifrance.com/lib/mx-mzda.htm mx5 mzda] [http://uo-ination.ifrance.com/lib/princess-pane/ princess pane] [http://lauashbu.ifrance.com/lib/mamma-mia/ mamma mia abba] [http://butanexlove.ifrance.com/lib/dvd-vergini.htm dvd vergini prezzo] [http://zonkismusik.ifrance.com/img/styles/ufficio.htm ufficio] [http://bagrec.ifrance.com/lib/knetconfig.htm knetconfig] 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 42: Line 42:
 
| valign="top"|
 
| valign="top"|
 
* Potentially very high rate of supply of hot water.
 
* 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).
+
* Can accomodate backup heating (e.g. electric immersion for gas boiler) and multiple heat sources (e.g. solar   gas).
 
| valign="top"|
 
| valign="top"|
 
* Supply runs cold when stored heat exhausted: takes time to re-heat.
 
* Supply runs cold when stored heat exhausted: takes time to re-heat.
Line 55: Line 55:
 
| valign="top"|
 
| valign="top"|
 
* 'Dry loft': no need for tank in attic.  
 
* 'Dry loft': no need for tank in attic.  
* Good pressure for showers & monobloc mixer taps even in attic spaces.
+
* Good pressure for showers
| 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 07:43, 31 August 2007

hangzhou wan domanda di insegnamento lbp 5200 legislazione amministrativa msi megabook s260 les amants de mogador profumi uomo giorgio armani suor piera cori mazziniano sec2 asus palmare mypal a620bt polti lecoaspira 710 kit harr potter aqua energiser big balls konica minolta dimage z5 ati fire gl riassunto generale promessi sposi assicurazione merano fhm com ph flag to flag brick champion chip stivali per uomo radio di r wiliams divx hd canvass videos de sexo virtual hamlet zelig music java com viaggi cecoslovacchia portavasi imo (fiume) disoccupazione yu gi oh sito ufficiale tetra pak www sepel com www easyjet it bagnetto bimbo ww google cl jupiter brevi deb e dave porno gratis en la red gore vidal wiso dvd recorder microsoft exchange 2003 rivali turtles 2 galactic teddy vidoe rete aziendale telefono per pc www alessandro it rassegna stampa konus 114 dragosta din tei ozone fiat voluntas dei rosa balistreri look for book spiaggia santa maria havana elettronica transistor colonia estiva acer notebook aspire 1692wlmi peter tosh piedi femminili pagina 21 cappotto cani extra large lord byron sandali miu miu neovo f 419 gelfo roveredo di gu bomba in italiano sfondi per telefonino video degli evanescence telefono registratore incentivi statali auto metano foto giovanna grande fratello 6 poliuretan the waves of love lupo tdi aculaser c1100 a4 color zuchero baila morena volvo 850 sw t5 tesina italiano lyell sir charles afs nikkor 1870mm f 3 54 5 g ed volkswagen vento 19 tdi gl website marketing strategy sesso be san francesco d assisi santo scheda video pci 6600 ddr 400 512 mb mp3 pro automobile usata vendita comune di alife siemens amilo v7010 simac gelatiere batterie musicali macro foto fotocamere digitali los canos hotels lago di garda hard disc portatile acer pda n30 gps spyware stormer free paswords trasmissioni meccaniche x gon give it to ya paese oga roma corfu biglietti aerei soluzione call center gradino step stefano scarampella ricevitore digitale terrestre strong passaggio da pubblico a privato audi a3 32 coppie porche nokia 6600 cavo hajjah oro pisa firenze mangiare bere www sexool com nephrolepis phentermine diet pill giochi da tavolo sexy martin pierre it s so be quiet pescara samsung tvc de geer gerard jakob diplo quick player oakley fives 2 0 bf srl bolzano software email marketing holding out for hero perreo en vivo stokke letto memory stick 1gb sony psp whirlpool forni a microonde martinica buap lultima rapina schiava e signora b c srl palawan modal shorts in amore legen of zelda il tempio greco euro convertitore manele mp3 driver per voodoo 3 intel pentium 4 2 8 ghz mx 3100 tony britten recetas smart media curcio alimentatore asus a730 harlem notturno nokia3310 europe musica cd frittelle crema latina oggi toner canon lbp810 notre dame de paris italian version sofia vergara nua xxx black women movie vree michele ranieri snc traduzione california phantom concerto air talkie roma dragostea din tei da scaricare marat safin etichetta alimentari rotting com no milk to day suncanom ferro mid congelatore electrolux lettori dvd thomson cavalcata stay whit me puffetta karaoke professionale garway ltd juliana do bb nua linksys psus4 diario di un italiano mini lavatrice automatica risultati concorso carriera prefettizia outlet torino corse con le macchinine a 21 macchine mx5 mzda princess pane mamma mia abba dvd vergini prezzo ufficio knetconfig 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 and why one would choose one rather than another. In particular the various types of mains pressure systems - unvented and thermal stores/heat banks - becoming increasingly common in the UK are discussed, as are solar and other renewable systems.

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. 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. 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:

PRO CON
Instantaneous
  • Continual supply of hot water.
  • Rate of supply limited by fuel supply/consumption. No backup when heater (e.g. combi) fails.
Stored heat
  • 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).
  • Supply runs cold when stored heat exhausted: takes time to re-heat.
  • Heat lost from store while not in use.
Mains pressure
  • 'Dry loft': no need for tank in attic.
  • Good pressure for showers