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| Thread ID: 71115 | 2006-07-27 01:18:00 | Hot water cyclinder:How does it work and how much power.... | lance4k (4644) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 473867 | 2006-07-27 01:18:00 | Ok i have a standard hot water cylinder at my house, if I used up all the hot water from it,does to hot water cyclinder use MORE power to heat the stone cold water back into hot water? And once and hot water has reached the correct temperature does it go into a kind of standby mode where it uses LESS power then when it's heating cold water to hot water? | lance4k (4644) | ||
| 473868 | 2006-07-27 01:25:00 | Its just like your electric jug, except it has a thermostat and should be well insulated to reduce most of the heat escaping out the sides.. When the water reaches the desired temperature, the thermostat switches off the power to the element. As the water slowly cools a bit, the thermostat will cut in, allowing the element to heat it up a little bit again so its always at the right temperature. The power used is dependent on the power needed to raise incoming cold to the set thermostat temperature. Use a little hot water, the overall temperature drops, the element comes on for a while. Use a lot, the element comes on for a lot longer. Power use is directly proportional to water running out the hot tap. Add to this that it may also be dependent on what tariff you are on with your power company, they may stop the element coming on at peak times, the re-heating will be delayed until off-peak. |
godfather (25) | ||
| 473869 | 2006-07-27 01:28:00 | The amount of energy needed to heat water depends on the quantity of water, and the temperature difference required. There is always a bit more needed, because the water isn't held in a lossfree container. You have to heat the cylinder (which is why cylinders always used to be made of copper --- its "specific heat'[ is small), and the insulation. When the water is up to temperature, the only energy used (as long as there is no draw off) is that needed to replace the losses through the insulation to the outer shell (where it is lost to the air), and any losses through conduction to the pipes. |
Graham L (2) | ||
| 473870 | 2006-07-27 01:34:00 | so here a 2 scenarious: 1)i use up all the hot water each day and the water is stone cold. 2)i DON'T use up all the hot water each day(say i only use half of the hot water) What scenario would use the MOST power each day? And how much approximate power do hot water cyclinders use per month on scenario 1 and scenario 2? |
lance4k (4644) | ||
| 473871 | 2006-07-27 01:41:00 | 1) The amount of power depends on the amount of hot water used (the amount of water running out the hot tap) 2) As above but if its the same cylinder, and you have only used half the heated water it will cost half as much as heating it from cold. We don't know the cylinder size, so we cannot tell you how many units it would cost to completely heat a stone cold cylinder. Again I repeat, the cost is directly proportional to the amount of water you use. There is no magic involved. |
godfather (25) | ||
| 473872 | 2006-07-27 01:42:00 | Try taking a cold shower each morning, it has a remarkable curative effect on the brain cells: www.associatedcontent.com |
Terry Porritt (14) | ||
| 473873 | 2006-07-27 01:55:00 | Say you've got a 200 litre water cylinder . Ignoring the losses: to heat 200 kg of water from 10 degrees C to 60 degrees will take 50x200 000 calories, which would be 4 . 184 x 10^7 joules, which comes to 4 . 184/3 . 6 x 10, 11 . 6 kWh . I think that's right . ;) If you use only half the water each day, you will use half that much electricity to heat it . Add a bit for the losses . If you use all that water in one long shower, you will lose less heat to the pipes . If the pipes cool down and have to be heated again you lose more . You pay to heat the cold water in the pipes which comes out when you first turn on the hot tap, remember . |
Graham L (2) | ||
| 473874 | 2006-07-27 01:57:00 | Bugger that, Buy an on-demand water heater. | Metla (12) | ||
| 473875 | 2006-07-27 03:27:00 | 11.6 kWh. I think that's right. ;) 11.67 kWh according to me, but I am not the pedant here... Bugger that, Buy an on-demand water heater. The on demand (electric) waterheater will use 11.67 kWh as well. Just no ongoing storage losses, but then the tariff is usually higher in c/kWh as its "uncontrolled load". Cheap answer - don't shower. |
godfather (25) | ||
| 473876 | 2006-07-27 04:07:00 | Those on demand gas water heater are the best ;) | SKT174 (1319) | ||
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