Cheapest way to use the immersion heater

Cardew wrote: »

So if it uses £1.50 for showering and is 'absolutely useless' how is the electricity being used?

Energy cannot be destroyed(according to the law of thermodynamics) so the heat must go somewhere.

I'm not sure what your trying to do here Cardew. But I didn't come on this thread to discuss my shower.

The question was what size of tank does one think best for family of 5. If you have an unvented direct tank and a family of 5 and think you can help with the question please do so.

If not, get your neck in! I'm not 'playing' today.

JennyR68 wrote: »

I'm not sure what your trying to do here Cardew. But I didn't come on this thread to discuss my shower.

Sorry I thought the quotes below indicated you were discussing showers!!

QUOTE=JennyR68
1. I've seen days when my family have used £1.50 to use the electric shower alone (teenage girls, why is it even when I've timed them and watched the monitor clock up they are still convinced they were only in '5mins'? ). It's days are numbered, waiting for plumber to put new unvented direct tank in now to run a mixer shower instead.

2. Electric shower on last legs, useless as well as expensive. However as completely redoing bathroom part of the makeover is replacing ancient water tank and we don't have to replace shower with another electric. Plumber advised putting in direct unvented as that is what one does these days. Gives pressurised hot water and will result in much better shower from a thermostatic mixer.

3. JennyR68 is complaining about paying a fortune for an absolutely useless shower, wouldn't care what she paid for a decent one!

I think the question is perhaps impossible to answer, so much depends on usage patterns and what is available to the user.
If you heat something up it will take energy, if you leave it stood it will cool down - eventually. No if's and no buts, it is fact.

I therefore think it is up to the user of the heated water to look at their needs and usage patterns before deciding what is right for themselves. If you use a little water occasionally then boil a kettle or use an equivalent means. Perhaps an undersink heater or instantaneous water hear will suffice. If you want a shower a day then an electric one is perhaps the way forward. Should you be fortunate to have a family then stored hot water will work for you providing you use it all and do not leave some to be diluted with cold water that will replace it.
I realise that this will lead to several arguments, firstly that the incoming cold water will be heated by the remnants of the hot water and so use less energy to heat up - But only if you heat it up straight away, and if you do not use it straight away then it will start to cool anyway. You will also use more energy heating water from a lower temperature if your tank is cold - So I really do not know the answer to this one.

A further factor to consider is heat loss, if your airing cupboard is warm then you are losing heat, if your pipes are hot then you are losing heat, this may be beneficial heat loss as it is helping to heat your home but it is all helping to cool your water down, so if you want to control your heat loss then insulate your pipes and tanks - Remember even a Thermos Flask cools down!

There is no totally efficient fuel, electricity is just about 100% efficient at the point of use but is expensive, gas is at best about 90% efficient at point of use but suffers significant losses in pipes and the waste of water as a combi boiler gets "up to speed" An unvented cylinder is nice as it will give you as good a flow as the mains will provide, the choice of heating up the water inside is up to the user, the use of the old copper cylinder I feel in this day and age is an anachronism, it is after all is said and done little more than a bulge in a pipe with hot water in it and has little pressure and many potential problems.

So what do I do? My kitchen sink is miles away from my tank so I have a 10 litre undersink 2Kw mains pressure heater, I use it as needed and it is set to a high (80 Deg C ) temp, it works for me as I tend to wash up infrequently and use a full load of hot water. It is plumbed in 10mm Hep2O so wastes about 200 ml of cold water before the hot comes through.
I shower daily so have a 9Kw instantaneous heater, it has been sufficient down to the recent -8 Deg C I have experienced. I also use this same heater to fill my hand basin for a shave and tooth brushing session, I can have a bowl full of hot water after 45 seconds or so at 9Kw ph and have no need to heat my cylinder at all.
If you want the convenience of hot water on demand then you are going to have to pay for the privilege, the second you make water hotter than the room it is in it starts to cool, yes, even as you heat it it loses heat, before it gets to your taps it heats the pipes and cools down, and then we let hot water go down the drain! This thread should make all of us think!
I will add that I do not have gas, my electricity bill is around £100 per quarter, my water cost me £6 per month (metered) but is in credit now, my coal bill is the subject of another thread! :eek:

argonout wrote: »

In a nutshell your looking at 2kw to 8kw a day heat loss with a well insulated to not well insulated system taking into account pipes/filling tanks having it on timed. Remember take off 4% off that if you have it on for an hour, 8% 2 hours etc.... 1hr on , 23hrs not being on constantly.........

argonout wrote: »

Hope this is clear??????????

Cardew, open your mind a little my friend

Jen, this was about cheapest way to use an immersion

Chill out guys, this site is for enlightenment!!

Welcome to the forum!

I am afraid I am not clear of the point you are trying to make, or at least why I need to open my mind?

You will find if you peruse this site, that many people think having the hot water on all the time will cost a huge amount more than having it timed. Some apparently are unaware of a thermostat or its purpose.

My point in this, and other, threads is that whilst a timer is obviously cheaper the difference is not massive.

So as an example take a HW tank that loses 2.3kWh in 24 hours when filled with water at 65C (as tested to a British Standard) - see below.

Even if you leave the tank on 24/7 you are not going to lose more than 2.3kWh a day.(and of course the lost heat warms the house - which is why it is often in an airing cupboard)

Having it timed will reduce this 2.3kWh loss.

Now perhaps you can explain why you feel I should open my mind?

argonout wrote: »

For instance if we say a tank reaches tempreture in an hour then if you use a tank a day have it on an hour before you get up. If you use half a tank then have it on for 30mins.

That's something YOU got wrong.
If a tank heats to the temperature you want in 1hr then you don't get half a tank in half an hour. You get the whole tank at half the temperature overall. Most of the hottest water may be at the top and coldest at the bottom but overall it will be half the temperature you need.
Before you condemn Cardew (who has shown to have a good knowledge of this subject and better than you have I might add) you need to make sure of your facts.