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hot water

Water heating is a heat transfer process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to steam have many uses.
Domestically, water is traditionally heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers. These metal vessels that heat a batch of water do not produce a continual supply of heated water at a preset temperature. Rarely, hot water occurs naturally, usually from natural hot springs. The temperature varies with the consumption rate, becoming cooler as flow increases.
Appliances that provide a continual supply of hot water are called water heaters, hot water heaters, hot water tanks, boilers, heat exchangers, geysers (Southern Africa only), or calorifiers. These names depend on region, and whether they heat potable or non-potable water, are in domestic or industrial use, and their energy source. In domestic installations, potable water heated for uses other than space heating is also called domestic hot water (DHW).
Fossil fuels (natural gas, liquefied petroleum gas, oil), or solid fuels are commonly used for heating water. These may be consumed directly or may produce electricity that, in turn, heats water. Electricity to heat water may also come from any other electrical source, such as nuclear power or renewable energy. Alternative energy such as solar energy, heat pumps, hot water heat recycling, and geothermal heating can also heat water, often in combination with backup systems powered by fossil fuels or electricity.
Densely populated urban areas of some countries provide district heating of hot water. This is especially the case in Scandinavia, Finland and Poland. District heating systems supply energy for water heating and space heating from combined heat and power (CHP) plants, waste heat from industries, incinerators, geothermal heating, and central solar heating. Actual heating of tap water is performed in heat exchangers at the consumers' premises. Generally the consumer has no in-building backup system, due to the expected high availability of district heating systems.
Today in the United States, domestic hot water used in homes is most commonly heated with natural gas, electric resistance, or a heat pump. Electric heat pump water heaters are significantly more efficient than electric resistance water heaters, but also more expensive to purchase. Some energy utilities offer their customers funding to help offset the higher first cost of energy efficient water heaters.

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  1. M

    No Heating or Hot water AlphaCD25C

    My partner has an Alpha CD25C fitted and worked until a couple of weeks ago. Intermittently it will switch off after working for 4-5 days. When checking the boiler lights A + B flashing red alternately and light D is green. Tried doing a reset and switching off the main power and restarting...
  2. A

    Hot water very slow new mains pipe fitted

    Hi all Just had a new mains water pipe fitted and the hot water is very slow almost a trickle. We have a combi vaillant ecotec pro 824 and it seems to come out fast to begin with then slows down considerably. It seems the boiler is struggling to provide hot water at the adequate rate that it...
  3. G

    Best economic way to heat hot water no heating

    Purchased property, all electric heating has combination cylinder doing hot water for 1 bathroom only , updating bathroom to have a shower, bath a basin and kitchen sink that needs hot water with no gas main or boiler , what’s the cheapest system to install to heat this property’s water...
  4. D

    Boiler shutting off during heating hot water

    I have a Viessman Vitodens combi boiler. When running the hot tap (or shower), the water comes through hot but then the boiler shuts off, water gets cool, boiler fires up, water gets hot, and so on... Only started happening a few weeks ago. I have replaced the flow sensor, checked voltage where...
  5. A

    Rayburn 499k heating working but no hot water

    Hi all, just this morning seem to have a new problem to us with our Rayburn. Oven and central heating all operating as normal, however we have no hot water from any taps. We would normally hear the Rayburn kick in when hot water is demanded… however it is not. Any help hugely appreciated
  6. M

    Hot water solution for cafe??

    Hi guys. Do any of you knowledgable lot have any recommendations for hot water in a small cafe kitchen? They have a combi boiler which serves the property but she’s been having issues with it which then means she can’t open due to having no hot water? Any advice would be great.
  7. R

    loosing hot water flow when macerator pump goes?

    Hello I have a salon and the plumbing for the hair wash basins is taken from the toilet, so when we are washing hair and the water is a good temperature, when the pump goes the water goes cold it takes a wile to come back. It used to do it a bit and now its much worse. A plumber said it cant be...
  8. K

    No hot water if the heating is running, but otherwise okay.

    I have a strange fault with a Vaillant EcoTec combi-boiler. It's 100% reliable whenever the heating is called for, ie. by the room-stats. It's also 100% reliable when hot water is called for, ie. hot tap or shower, as long as the heating isn't running at the time. But if the heating is already...
  9. Bookalon

    hot water cylinder control valve

    Hi, I have an oil burner which is controlled via Tado to heat my home. My hot water cylinder is heated with water from the burner and also has a dumb immersion. I don’t use the immersion at all And would like to replace it. The burner heats the water in my hot water cylinder with a TRV valve...
  10. A

    Worcester rsf hot water cutting off

    Hi.i was asked to take a look at my customer worcester 28i. When calling for hot water the boiler fires up fine and the water gets hot. After approx 30secs of running hot water the boiler shuts down. With the hot tap still running( water gone cold) the boiler then fires up after about 5sec and...
  11. yngndrw

    Which Controls: OpenTherm with Hot Water Priority

    Hello all, I'm looking for suggestions on heating controls. We'll be upgrading our boiler (To a modulating oil system boiler - EOGB Sapphire) and unvented cylinder (To a Mixergy cylinder) as we currently have a 13 year old fixed output combi boiler with a unvented cylinder which is fed solely...
  12. P

    Heating works but not hot water

    I have an Ideal combi isar HE 24. Heating works perfectly but hot water does not at all. Turn any hot tap on and water gets luke warm after about 10 seconds then boiler disengages and water gets cold again. Been told it could be thermistor, or a couple of other things. Can anyone please help?
  13. M

    Intergas HRE 30 SB - Hot Water colder after engineer visit

    Morning All. I hope you can help. We recently had a (mostly) successful visit by an Intergas engineer who fixed problems with our boiler randomly turning off. However. Since his visit the hot water has been noticeably cooler than it was before. I’ve tried to change the temperature of (DHW)...
  14. P

    Intermittent hot water problem wb combi

    WB combi has recently had it's annual service. It has been working reliably up to that point for many years. Now we keep losing hot water - temps on boiler increase over 100 on the display and it shuts down heat. Engineer claims it's coincidental and must be a blocked heat exchanger that has...
  15. R

    Hot water coming on combi sometimes other times not

    Hi guys thankfully not been needing to com on for a while but could do with a pointer. 2 weeks ago I noticed boiler didn’t fire for hot water in kitchen which is next to boiler and cold main in, it came on after a few seconds longer than norm I thought just a blip, but this weekend and since...
  16. R

    Baxi 228 combi boiler hot water flow rate poor?

    Hi, Just checking I'm not talking rot. Today I visited a house with a Baxi 228 combi boiler. The technical spec for the DHW output is shown in the image. Boiler was installed 27 months ago. Baxi is claiming 13.3 litres @ DT 30. I set the boiler DHW temperature to a high setting. I was...
  17. H

    Benefits of one large hot water tank over two in parallel?

    A friend is building 5 en-suites above his pub. An advisor has said he needs a 64kW gas boiler to heat 7-8 radiators and an 800-1000 litre water tank to make sure guests have hot water when they need it. This seems way over the top to me - especially as it's not guaranteed that there will always...
  18. S

    Unable to run bath of hot water after boiler change

    Heating System Have 2 houses where identical Heating systems installed (self & neighbour) In Dec both Baxi boilers were replaced with Viessmann Vittodens 30W due to ageing reliability issue. System is as per drawing Hot Water Draw off Thermal Store operates by the process that as DHW is drawn...
  19. Ted808

    Worcester greenstar, Hot water intermittent.

    Heating works and hot water- sometimes, but I noticed when I turn the hot tap on the pressure gauge drops to zero. I've not seen this before. Topping up the pressure doesn't seem to make a difference. As soon as the heating only is on pressure goes back up to 1.5bar. The thing is the flat is...
  20. K

    Hot water no heating

    Hi, I have just had me diverter valve and cartridge replaced so solve my original issue of have both heating and hot water on at the same time without the option to turn off. But now I can’t turn my heating on. It’s on, on the boilers thermostat but doesn’t heat. I’ve disconnected all other...
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