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hot water

Water heating is a thermodynamic 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, 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 and Finland. District heating systems supply energy for water heating and space heating from waste heat from industries, power plants, 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.

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  1. L

    Help... intermittent hot water issue

    My heating has developed a new and unwelcome quirk just recently, which is that it's sporadically failing to provide hot water. This is something that happened a few weeks back, but it seemed to go back to normal, but in the past couple of days it has happened again each day. We have a...
  2. S

    Vented Hot Water Cylinder Without Vent Pipe!

    After calling a plumber to look at our leaking power shower he discovered that there is no vent pipe coming off the hot water cylinder . The cylinder is an old indirect vented cylinder heated from the central heating boiler and has a secondary electric immersion heater that is disconnected...
  3. T

    Worcester Greenstar 30CDi info please

    Hi Is the Eco button for the heating of the radiators, or the domestic Hot water? The reason i ask is there is also an E setting on the Hot water control Knob. When i had a Baxi(old house), the domestic hot water always had priority. which seems logical. How does a worcester bosch handle it...
  4. M

    Hot radiators remain when heating goes off - maybe from hot water storage cylinder ?

    Hot water coming out of the hot water storage cylinder into upstairs radiators after heating/HW turns off and running out of hot water in the mornings. I have a Glow Worm 24HX Condensing boiler on the ground floor with a pump in the same cupboard, a hot water storage cylinder in the airing...
  5. L

    Question on upgrading hot water cylinder

    Hello, I am looking into upgrading various parts of my residential block's heating and hot water system, which serves 12 flats that resulted from the conversion of two adjacent terraced houses. Our current hot water cylinder has 1000 lts capacity, is vented, is heated indirectly through a gas...
  6. elvis80

    PEX-AL-PEX for hot water return (manifold system)

    (Bear with me this is my first post on here...) We're putting in a manifold system for the H+C in the bathrooms of our new house (self-build). What are everyone's opinions on using PEX-AL-PEX pipe for our hot water return system, please? Good or bad idea? The pipe says: Tmax 95 degrees C / 10...
  7. S

    Getting a Remote Control RFWRT thermostat talking to a Worcester Boiler 28i

    Getting a Remote Control RFWRT thermostat talking to a Worcester Boiler 28i, changed the batteries, no heating, hot water working ?
  8. M

    Thermal store combi boiler, hot water flow rate.

    Can anyone tell me the hot water flow rate on a thermal store combi boiler? As opposed. To a 40kw combi that will deliver nearly 16litres per minute. And any recommendations for a good thermal store boiler thanks.
  9. C

    Heating / hot water glitch ?

    Good day . The heating and hot water on my vaillant boiler work fine independently . If my heating is on and a hot water tap is opened or shower used - the heating [ if on ] refuses to come back on and if left will stay off . If I hit the reset button the boiler will fire and the heating comes...
  10. C

    Heating won't come back on after using hot water tap / shower

    Good evening . I have a Vaillant boiler that although the heating and hot water work perfectly independently the heating if in use will not come back on after using a hot tap or shower . If I press the reset button the heating will come back on but will not do so on it's own accord . Any advice...
  11. Bbarclays

    No hot water open vent glowworm fuelsaverMKII R40

    Hi there Today friend was changing radiator valves, so he drained system, put radiator valves, new radiator. I notice TRV valve was on cold end- return or out line from radiator. I asked my friend to relocate TRV valve on inlet side. (when heating started, hot water was coming from white plastic...
  12. M

    Hot water temperature problem

    I have a Glow Worm 24HX Condensing boiler on the ground floor with a pump in the same cupboard, a hot water storage cylinder in the airing cupboard upstairs (Kingspan 1500 x 450 grade 3, 162 Litre. cylinder) in the eaves area I have another pump (both pumps are Salus MP200 domestic circulating...
  13. J


    Hi all, Over the last month we noticed water coming out of all the hot taps and shower would only come lukewarm. The puzzling thing is control unit states that the temperature in the unvented cylinder is at 69-70 degrees celsius. When I’ve I released water directly from the cylinder and felt...
  14. B

    hot water on combi boiler setting query

    Good morning, I have a query about the water dial on my boiler bought a few months ago (Vokera Easi-Heat Plus 25C Boiler) and apologies for no pictures. My hot water is fed via the combi boiler and cold water is mains fed. There are two dials under the flap one is for hot water and the other...
  15. S

    URGENT no hot water of heating

    I have no hot water or heating, my boiler has no error symbols, my cylinder has gone cold, pump seems to be working well it’s making the same usual noise/vibrations, pipe under th boiler are hot but none near the cylinder is! Can anyone help
  16. P

    Hot water but cold rads

    I have a Worcester Greenstar Ri Woke up this morning with plenty of hot water but a cold house. All the rads were luke warm. From searching online I tried switching the 3 port valve to manual. This seemed to result in the boiler heating and the rads became warm, however this only lasted for...
  17. S

    Clunk when switching on hot water heating system - non vented system

    Hi, about 5 years ago I had a new boiler fitted. The location of the boiler was moved so new pipes fitted. No problems. About 2 years ago I then needed to have my 3 way valve replaced, this is when issues began. Initially there was no heat and the system was drained several times, this...
  18. T

    Glow Worm Ultimate 30 C hot water but no heating.

    Hi everyone, hope you're all well and hopefully someone will be able to help with a problem I have. The boiler seems to fire up with heating no problem at the start of a program but will randomly stop heating. There are no error codes on the boiler and the thermostat (Climapro 2RF) shows no...
  19. A

    Clogged Faucets and Low Hot Water Pressure on 1 faucet

    I have 2 issues/questions. To start from the beginning, we just purchased and moved into a home at the beginning of November that has a private well, once we moved in I noticed we had water pressure issues. Upon investigation I found that all the faucets/fixtures with pressure issues were...
  20. C

    Whistling sound coming from Hot Water Cyclinder

    Hi there, I have a joule cyclone twin solar unvented pressurised hot water cylinder that is floor standing. Just recently, I have noticed when I turn on the hot water supply taps anywhere in the house, a whistling sound starts to come from the tank itself. It gets louder the more you open the...