Economy 7 confusion

[Rickster1978]

Hi all.

I’ve been using the search on the forums quite a lot to find really useful information which has helped in the current property refurb I’m working on. So thanks all

Now I have one thing that I’m a bit stumped on. The flat I’m refurbing has Economy 7. It’s a new electric meter which is the ES-12B I’ve seen used quite a lot so think it’s pretty common.

All the wiring has been replaced and we’re starting from scratch. I’ve bought a twin tariff fuse box consumer unit and I’m now questioning if I actually need it as the smart meter charges the different tariff based on the time.

We’re using new Elnur storage heaters and they only have one feed as the time is controlled on the storage heater itself. So they will be on the peak CU.

Now my confusion lies with the immersion heater. We’ve got two feeds going to the water tank. I assumed we’d need a peak and off peak feed. However the economy 7 controller only allows for one feed into it. So that leads me to the question as to whether we even need an off peak CU. If the hot water is only going to use one feed would we just use the peak feed which would charge the off peak rate based on the time that it’s used.

Now if we do only need one feed from the meter, what do we do with the second tail (the off peak one). Should we just terminate it or is this going to cause issues with the electric company.

As it is we appear to have a dual tariff consumer unit with an SPD for each side of the board but only any actual outputs from be peak side. Just thinking it would be cheaper to exchange it for a normal CU.

Any advice would be greatly appreciated as I’m a little stumped as to why we have two cables going to the tank but an economy 7 controller which only seems to allow one.

 

[bhm1712]

On most modern economy 7 installations, with digital or smart meters - as you say, there is no “switching” done. The rate change is done on the meter based on the time and it will display the 2 rates separately. There is no longer a need to fit separate off peak circuits. Your entire dwelling can run on the off peak rate based on the electricity meter and from one central CU.

 

[EFLImpudence]

There are timers with boost switches for connecting two immersion elements to one circuit.

 

[Rickster1978]

Thanks both. The timer I looked at does have a boost for the top immersion heater so it’s the right one. I’ll take the dual tariff CU back and get a single one as there’s no need for separating out the circuits. I did do a little test last night and left a light on over night to check that it charges to the other tariff. I’m sure it does an automatic switch over at night but was keen to check