I agree john, but until i see the bills i do not even know if they are being charged for the economy 7 ? if they are i will contact dno to remove economy 7 meter
immersion wiring help
- Thread starter sajeel
- Start date
I agree john, but until i see the bills i do not even know if they are being charged for the economy 7 ? if they are i will contact dno to remove economy 7 meter
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Surely it means they'll be paying more for all the normal rate lecky they use ? Anything they use off-peak will be cheaper.
But whether it works out depends on what they use.
IF they have a sufficiently large cylinder and can heat their hot water (or at least most of it) at night on off-peak rate, and they don't use too much during the day, then they may well save. It takes a lot of lecky to heat water. If (picking numbers at random) they use 100l/day, and it's heated by 50˚C (eg from 10 to 60 or from 5 to 55), then that'll take 100 * 50 * 4.2 / 3600 units/day (kWhr/day). That's 5.83 units/day.
Use more water, or heat it hotter, and the unit count goes up.
One obvious way to make best use of off-peak is to have two cylinder stats - one high up (say around 1/2 way or higher) and set at the minimum temperature you generally need. That controls the day-time (expensive) heating if you need it.
Then have a stat high at the bottom of the cylinder (as far down as the IM heats) set very hot. That controls the IM on off-peak and puts as much energy as possible into the cylinder. Then mix the water down with TMVs to avoid scalding hot water at the taps.
If (picking more random numbers) the mains comes in at 5˚, the cylinder is heated to 90˚, and you want water at 45˚ - then the effective capacity of the cylinder is doubled as for every 2l you draw from the hot tap, you use 1l from the cylinder and 1l from the cold mains.
However ...
What hasn't been said is how the property is heated ! It sounds like there are no night storage heaters, so what's replaced them ? If it's (say) gas central heating then the obvious recommendation is to heat the cylinder from the gas boiler and ditch the E7 tariff.
You mean contact the customer's supplier (ie the name at the top of the bills) ? The end user doesn't deal direct with the DNO - only with a supplier who then contracts with a meter operator and the DNO to physically provide the service.
If nothing is connected to the off-peak meter, as indicated by OP, then all electricity will be charged at the E7 day rate, which is higher than the single tariff rate, and nothing will be charged at the E7 cheap rate.
That's precisely what I do - heat two, large, well-insulated cylinders of water overnight. However, that in itself would get me nowhere near the 36.7% night usage I need to even break even.
I need to think about it, but I'm wondering about those ('random') figures. 5.83 kWh/day is about half of the average total electricity consumption per day of a UK household.
Kind Regards, John
That's a point, but I find it hard to believe that they will have been left with a cheap rate meter if they are not on an E7 tariff (a peep at one of thir bills would clarify). BTW, it's their electricity supplier (not DNO) that they need to talk to to change their tariff. Removal of the E7 meter would then automatically follow.
Kind Regards, John
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Do we know that there is definitely a separate meter ?
"there is second consumer unit connected to economy 7 meter" could mean there's a second meter, or it could mean that there's a second CU connected to the one dual-rate (aka "Economy 7") meter.
In any case, even it it's 2 meters, it wouldn't be all that hard to rig up and autoswitchover to run everything off the off-peak meter when it's on
Hi John thanks for pointing that out, you are correct it will be supplier not dno i was thinking of new installs. i will wait for bill and then upload costings so we can close this thread, lol.
Probably an under-estimate of consumption - the numbers were picked to make the maths easy to follow. If a shower is (say) 10l/min then a 10 minute shower would use that with nothing left for washing hands/dishes/clothes*/etc.
* Although it seems most washing machines these days go "efficient" by using the most expensive means of heating water - ie cold fill and electrically heat it rather than use whatever hot water supply you have
That appears to be what we are being told ...
It wouldn't. However, it would be even simpler to ask the supplier to install a single dual-tariff meter, which is the way that most E7 (etc.) setups are arranged these days. However, I still think some careful sums need to be done to make sure that retaining the E7 at all is cost-effective, since I still doubt that a single immersion heater alone (plus other small nocturnal loads) is going to even hit the break-even point. Don't forget that, as I wrote to BAS, I have to average appreciably more usage/hour during the night than during the day in order to break even.In any case, even it it's 2 meters, it wouldn't be all that hard to rig up and autoswitchover to run everything off the off-peak meter when it's on
Kind Regards, John
I'm not disagreeing with the maths. 10l/min is towards the upper end for showers and, of course, even then, if the hot water is at 60 ° the amount of hot water used by a mixer shower would probably not be much more than about half that figure.
It's certainly not unreasonable to assume that one wants the immersion to bring a, say, 100l cylinder of water "up to temperature" overnight. However, at least in my case (unless I have lots of visitors etc.), the water is still pretty hot (well above body temp, so probably 45°-50°) just before the immersion "comes back on" (at night), so it probably doesn't have to raise the temp by much more than 10°-15°, certainly nothing like 50°.
Kind Regards, John
Hi people,
sorry for delay was waiting on customer to get bill information.
Here is the costings(economy 7);
Old Tarrif
18.30p/kw day
6.75p/kw night
Standing charge 18.90p daily
New Tarrif
16.71p/kw day
6.12p/kw night
Standing charge 18.09p daily
Both prices are with edf, when she phoned in to find out charges per kw they offered some better prices. let me know your thoughts if we should keep economy 7 or not.
sorry for delay was waiting on customer to get bill information.
Here is the costings(economy 7);
Old Tarrif
18.30p/kw day
6.75p/kw night
Standing charge 18.90p daily
New Tarrif
16.71p/kw day
6.12p/kw night
Standing charge 18.09p daily
Both prices are with edf, when she phoned in to find out charges per kw they offered some better prices. let me know your thoughts if we should keep economy 7 or not.
There's not too much "working out" needed - the figures for how much is used on each tariff will be on the bills....
OK, I'll rephrase ...
Work out how much could be used off-peak without too much hassle.
That's a bit harder and will involve some guesstimation. The obvious candidate is heating the water overnight - whereas I suspect it's done "as needed" right now". That means some estimating of hot water usage etc etc.
Then there's things like washing machines* and tumble driers which we'll ass soon be expected to run overnight if the smart meter evangelists are to be believed.
And err that's about it in most houses unless you're nocturnal.
* The modern "efficient" ones designed to expensively and inefficiently heat cold water rather than using the hot water that's already available.
Work out how much could be used off-peak without too much hassle.
That's a bit harder and will involve some guesstimation. The obvious candidate is heating the water overnight - whereas I suspect it's done "as needed" right now". That means some estimating of hot water usage etc etc.
Then there's things like washing machines* and tumble driers which we'll ass soon be expected to run overnight if the smart meter evangelists are to be believed.
And err that's about it in most houses unless you're nocturnal.
* The modern "efficient" ones designed to expensively and inefficiently heat cold water rather than using the hot water that's already available.
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