ELECTRIC WATER BOILERS

[ericmark]

We can select when water is heated, and how much water is heated, and how good the insulation is keeping the heat in. In an old caravan I installed a 1 kW 7 litre under sink water heater and the cupboard did not seem to get warm, and when the power had been tripped all day, I still had hot water, (12 volt pump) so clearly very little loss.

However in this house even a 40 gallon cistern will only stay warm 3 days. We use the heat to air cloths, and clearly the insulation is rather poor. Some of the new tanks

clearly have a lot better insulation, and using the Willis immersion heater system

you can control exactly how much water you heat by how long it is heating for, however the question is if worth the expense? OK the Willis immersion may only cost £35 but it will cost a lot more than that by time it is fitted.

I don't often have a bath, mainly shower, and I am sure a shower it cheaper to run, but much is down to how much electric you have, instant heat sounds good, but I looked at it here, 5 areas of the house have hot water, 2 kitchens 2 bathrooms and a shower room likely also laundry room but washer is cold fill so not used, there is a 60 amp supply to whole house, and things like hot taps often need a heavy cable to supply them and you loose room under the sink, even if there is enough supply to house.

So to fit hot taps is around £1000 per tap, may be more, so even if it can save money in the long run, with just 10% interest on the money has to save £100 a year to break even, so is it worth it?

 

[endecotp]

day timer which I had put in for the top

Why? How long is it on for?

my night time usage was greater than my day!

That’s what I’d expect. What’s the problem?

 

[JohnW2]

my night time usage was greater than my day!

That’s what I’d expect. What’s the problem?

That's certainly what one would hope for but I wouldn't actually 'expect' it for the OP, since I wonder how, with no storage heaters, he manages to get such a high proportion of night usage.

As I've said, I don't have storage heaters either and, like the OP, my main night-time usage is an immersion. I do manage to achieve around 45-50% night time usage overall (which makes E7 financially advantageous) (see graph below), but that's only because, being 'semi-nocturnal', I run most other large loads (WM, DW, Tumble dryer etc.) at cheap rate. Were it not for that, I don't think I would achieve the 35%-40% night-time usage threshold below which, with most suppliers, E7 becomes more expensive than a single-rate tariff.

I therefore wonder how the OP achieves (a little) over 50% night-time usage - something which (as you can see below) I have hardly ever achieved since improving the insulation on my HW cylinder (hence reducing immersion usage) a couple of years ago.

Kind Regards, John

 

[Neil McIlquham]

The cause is no timer on e7, eco 7 is now off and I am using day meter for 2hr boosts!
So a new boiler would not be any cheaper?
Just put a timer on eco 7 bottom tank!

 

[flameport]

When E7 is active, the hot water cylinder will heat up - but only to the point of it being hot, after that the thermostat will switch the element off, regardless of whether the E7 supply is still on or not.
Even if totally cold, that would typically only take 2 or 3 hours at most, which is between 6 and 9 units of electricity.

If you are having to use 2+ hour boosts in the day, then either you are using an absolutely vast amount of hot water, or there is something wrong with the lower E7 element.
A 4ft high cylinder would be around 120 litres, far more than would normally be required for a 1 bedroom flat.

However from these usage figures:

Your actual usage in the last 12 months Day 2,376, Night kWh 2,792 kWh

there doesn't appear to be anything wrong - 2792 on night rate is about 7.5 units per day, so entirely in line with what would be expected from heating hot water overnight, plus a small amount extra for whatever else is switched on overnight - typically very little, only items like a fridge / freezer.

Day use is about 6.5 units per day, certainly not excessive, and presumably that includes some form of electric heating?

So a new boiler would not be any cheaper?

Assuming the cylinder is properly insulated - no.
Even if it's an old one with little or no insulation, just fitting insulation to it would be a much cheaper solution.

Just put a timer on eco 7 bottom tank!

You don't need one - the E7 supply is timed by the electricity supplier, and you can't heat the water above the thermostat setting even if it's on for longer than the 2 or 3 hours that would normally take.

 

[Neil McIlquham]

The tank is well-insulated covered in foam.
No need for e7 timer and stop 2hr boosting every other day!
switch e7 back on, no washing machines or anything, only for water
No need to do anything!

 

[Neil McIlquham]

And no point in changing the tank now?

 

[JohnW2]

When E7 is active, the hot water cylinder will heat up - but only to the point of it being hot, after that the thermostat will switch the element off, regardless of whether the E7 supply is still on or not. Even if totally cold, that would typically only take 2 or 3 hours at most, which is between 6 and 9 units of electricity.

Indeed. The first graph below is a recent (pretty typical) day's behaviour of my immersion, with the main (thermostatically controlled) 'on period only being about 1 hour. Had the timer not 'disabled' the immersion at the end of the cheap period, there would only have been occasional very brief 'top-ups'. The second graph shows a day when a a fair bit of hot water (but less than a whole tank) had been used during the preceding day but, even then, the main 'on period' was less than 2 hours. On the rare occasions when the entire tank of hot water gets used, it takes 2.5-3h. ...

However from these usage figures: .... there doesn't appear to be anything wrong - 2792 on night rate is about 7.5 units per day, so entirely in line with what would be expected from heating hot water overnight, plus a small amount extra for whatever else is switched on overnight

Indeed. As I said above, definitely in a similar ballpark to my immersions usage.

Kind Regards, John

 

[Neil McIlquham]

Economy 7 meter going

 

[SimonH2]

That's not really the right sort of timer for your system.
Normally you would not use the upper element at all - it's really only there for when you use a lot of hot water and run out. If that happens, you switch on the top element and it heats the water in the top part of the cylinder - at expensive peak rate. You can buy timers design for those - they are normally off, and you press a button to get a boost for a while, after which they turn off. What you don't normally want is to use peak rate on a regular basis to heat your water - that just costs you more.
You should have either two consumer units, or a split one, with some of your loads (specifically in this case, the lower immersion) fed from the off-peak side. As said, this will come on when your electricity is cheaper - and you fully heat the tank on cheap rate. Switching will be done either with a time clock, or more likely, a radio controlled switch.

Ideally you try and use as much of your lecky usage on the cheap rate - that saves you money. If you really want to go all-out for this, you run things like washing machines and tumble driers at night - you need to check when your cheap rate is.

Can you get a photo of the meter and CU, just so we can check ?

 

[Neil McIlquham]

no meter on the e7 apart from one in the pic, only e7 use is for hot water!
nothing else runs on it no washing machine, no dishwasher, no storage heaters, just hot water for me