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I guess we have to agree to disagree.
Use of immersion heater in summer v central heating for DHW?
- Thread starter ericmark
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And the cost of the control device, which, if you have a gas boiler, makes it an unprofitable proposition.
For example, £300 to buy plus installation.
My gas usage in summer is about 50p a day.
My gas usage in summer is about 50p a day.
True, if one wants an automated system - but (although I haven't thought about this very deeply), provided one has the ability to think, there might well be some much cheaper (albeit less convenient) approaches?
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That is not what happens....
The hottest water will collect/congregate at the highest point, but then the interface between hot and cooler water, will gradually work its way down the cylinder.
I suppose we'll have to
I can speak only of personal experience. Starting from 'cold', it takes around 2.5 hours to heat all of the water in my 140 litre cylinder up to 'design temperature' using a 'bottom immersion' (theoretically 2.4h to heat 140 L from 18 to 62 with 3kW, ignoring losses). Again starting from cold, within probably 15 mins, certainly no more than 30 mins, of switching on the bottom immersion water drawn from the top of the cylinder feels 'as hot as one would expect' (i.e. close to 'design temp'), but becomes 'cold' pretty quickly if one keeps drawing it.
If significant heating of the water throughout the cylinder had been happening for that 15-30 mins, the water at the top of the cylinder (and everywhere else in that cylinder) would be very much colder than I experience. The sums are simple enough - if all 140 L were being heated by 3 kW, the temp rise should be about 4.5°C after 15mins, about 9°C after 30 mins - which isn't much.
Quite so, but not a lot of that 'working its way down' will have happened when only the tyop few inches of water in the cylinder is fairly hot.
As I've just written, my personal experience definitely confirms/supports that.
Absolutely no need, the article you just posted, confirms what I said happens. It's known as 'stratification'. Warm/hot less dense water, rises to the top, cooler denser water falls. In a cylinder, the interface between layers, will gradually drift down, as the overall temperature increases..
But a route for actually getting it from A to B might not be - at least, without ripping into the decor.Why? 'Wire' is freely available
I don't really understand what people are arguing about. As you say, it's called stratification, and means that the hottest water will always be in the uppermost stratum. with progressively lower temps in the strata below ... and when the average temp of all the water in the cylinder is relatively low (e.g. not long after the heat source at the bottom was turned on) the water in that uppermost stratum will be much hotter than that lower down.
In the fullness of time, if the heating continues, most of the water in the cylinder will be heated to a 'similar' temperature.
Sure, but eric seemed to be making a fairly general statement, which is why I asked 'why?'
In bigger hot water storage vessels stratification is a serious problem and frequently destratification pumps are fitted which often pump water from the bottom of the vessel into the top (this is in no way the fixed method) in order to breakup the layers. Sometimes the pumps serve a second purpose of hot water recirculation, although really they are 2 different functions.
i would love to see this electric shower that gets water upto temp in 3 or 4 seconds
Also immersions in a standard 36 inch cylinders are not 9 inches in length but 27 inches so you would not be heating just the top 9 inches of the cylinder
Also immersions in a standard 36 inch cylinders are not 9 inches in length but 27 inches so you would not be heating just the top 9 inches of the cylinder
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Access over to floors to install the wire is simply not there, so wireless is only option.Why? 'Wire' is freely available
But first question is why do I want DHW? If I want it to take a bath, then clearly top 9" is useless, but I don't, I want enough water to wash hands, and the odd dish when I do not want to wait for dish washer, and 9" is ample for that, so looking at why I want hot water, the question is more about why heat a whole tank of water when only 9" is required, except for the odd time I want a bath?
There is however a benefit in heating more water when using solar, as one may not have solar every day, however when I don't have enough solar it is clear to see,
and it is rare in the summer, replacing the immersion heater for a longer one, or using a simple timer instead of the iboost+ and using off peak would be far cheaper to running cables to control the boiler with tank temperature, so no point.My point is I have without changing anything two methods to heat DHW in the summer, and until this year I have always used the oil boiler option, this year I have moved to electric, and I have realised electric is actually far cheaper than oil, OK the tariffs vary, we have 4 stages of cost. 1) Free as not getting export payments. 2) Off peak. 3) Cost of loss export payments. 4) Peak electric cost. And due to losses even at peak electric cost, still seems to be around break even point, and with electric the temperature is more reliable as will oil it was controlled by boiler run time only.
In the past I had just accepted electric costs more than oil, and had never tested it. Seems I was wrong.
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