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Electric shower, anything I can do?
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richard.cs:

--- Quote from: soldar on July 25, 2019, 12:38:03 pm ---
--- Quote from: Someone on July 25, 2019, 11:25:15 am ---All the units I'm familiar with do have power control with ratios over 20, even beyond a factor of 30 so based on your choice of numbers they work fine. This is going back 20 years so its nothing new or exclusive, there are multiple suppliers of products which meet those requirements.
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I am interested in this. I'd like to see a gas water heater that can modulate output from say 12 KW down to say 500 W. Sounds very interesting. 

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Same, in the UK I've not seen anything near 20:1, many are more like 4:1 and 10:1 is considered to be very good. Once you go below their minimum they either cycle and the temperature swings wildly, or just turn off and go cold.
soldar:
Storage tanks also are necessary and useful when using solar panels to heat the water. While I lived in America my house had solar panels and a big tank and I hardly ever needed supplemental heat, only a bit in the winter. In the summer though I had more heat than I needed and I would flush the toilet with buckets of scalding hot water. 
Nauris:
For reference I draw schematic how hot water and heating is arranged here traditionally. (altought these days heat pumps are very much in, oil not so much)
soldar:

--- Quote from: Nauris on July 25, 2019, 07:06:33 pm --- For reference I draw schematic how hot water and heating is arranged here traditionally. (altought these days heat pumps are very much in, oil not so much)
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The problem with using a heat exchanger in the big heating tank for domestic hot water is that (1) you need the big tank always hot, which makes no sense when you do not need heating, and (2) efficiency suffers.

On demand combined heaters here do that and it works for certain values of "works". One advantage of not heating the domestic hot water directly with the flame but through an exchanger is that is adds a lot of temperature stability but, again, efficiency suffers a lot.

Another thing I would add is that if they are not required by code I would still require thermostatic valves anywhere a person might get hit by that water. All bathroom, kitchen faucets, etc. Most people do not realize how dangerous hot water is and how fast it can scald. I know of a very serious case of a baby in a bathtub who pulled the control lever and got badly burnt. If you do not have Thermostatic valves installed and you have children, old people, distractable people, etc. in the house you should really consider lowering the heater temperature as much as possible.
paulca:

--- Quote from: Someone on July 25, 2019, 11:25:15 am ---If you can't possibly wash you hands in the kitchen with 43 degree water while someone else is showering, or wait for them to finish their shower before running a washing tub at 60 degrees, then you've got some first world problems.

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So you are suggesting that when I want hot water of X degrees for X purpose I put my shoes on and go out to the boiler and set the hot water temperature manually and when I then want to use the water at Y degrees for Y purpose I go and change the temperature at the boiler again?

Who does that?  In fact most combi boilers with on demand hot water are just set at MAX and you mix hot and cold at the demand with a mixer tap.  They are of course differential, so if you want a low temp, it's mostly cold and very little hot is used.  The boiler will put out hotter water with a lessened flow, but it's really not an issue and surprisingly easy to balance by moving the tap, or shower valve.

The benefit of this approach with a shower is that you must mix a bunch of cold into the hot, which gives you even higher pressure.
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