How to setup hotwater for off peak only?

Crabs999 said:

If they are 'on', is that not going to override the BX2000? Should they not be off?

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Usually it's just the opposite. The two lower switches should be fed from BX2000. So, when the BX2000 switches on, if the lower switches were off the power from the BX2000 won't be able to reach the elements. That will be the case if the cables leaving the bottom of the switches go directly to the immersion heaters. One cable to each heater. However, @ericmark is correct two cables to the immersions is odd, so they may be getting a supply from somewhere else. One cable to each is how they would normally be wired as per the diagram below.

Crabs999 said:

I have noticed that if I flick the 'normal supply' and 'off-peak supply' switches on the BX2000 to the on positions, this light comes on and stays indefinitely. The boost buttons also do not do anything. I cannot recall what happens if only the 'off-peak supply' is turned on.

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That sounds like it has a permanent electricity supply wired to the off-peak side. Investigation is required.

With the 'normal supply' switch 'on' pressing the 1 hour boost should light the 'boost' light below for one hour, after which it should go off. It shouldn't be affected by the position of the off-peak supply switch.

Crabs999 said:

We have two electric heaters. There is no gas in the flat. I agree I don't think the switch for the lower immersion is economy 7, so I think we need to use the control box?

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If these heaters are panel heaters which you can turn on and off during the day then I would say that having E7 could be more expensive.

This is because they reduce the night rate BUT increase the day rate so unless you can always use a lot of electricity at night then it’s not worth messing around.

What has your landlord told you?

Can you post a pic of the meter and the wiring coming out of it and one of the front of fuse box too?

The Horstmann control unit would normally use 2 separate sets of cables - one that runs all the time (peak) and the other would be from the switched side of the meter and turns on @ off peak times.

The old Horstmann control should be wired like that whereby the top normal supply would be on all the time and that then powers the boost function and that would normally control the top element. The bottom off peak supply would only come live when the meter switched it on and that would then power the bottom element to heat the whole tank with cheap leccy. A lot of the new smart meters don't have dual outputs anymore and their rate just switches over when the timeclock reaches the economy 7 times and they then have 2 readings. If this is what's happened and the control system wasn't changed properly then, using the 'off peak' switch wouldn't make any difference until the meter clicked over to economy 7. By the sounds of it though the controller has been bridged inside so the off peak switch only works when the normal switch is on.

If this is the case then all you could really do just now is switch off the lower element switch until the economy 7 times are reached then switch it on until you get an electrician in the take a look. You should let your landlord know though as they are ultimately responsible and should be paying for it to be put right

OK so not being an 18th edition electrician but having worked with both of these systems with electricians when installing them I can make a bit of an educated guess.

The meter is a single outlet, so only one supply. The meter will be programmed to switch between 2 different tariffs, if you are on a economy 7 which is a dual tariff. The room heating circuits are on bays 3,4 & 6. Bay 2 is holding a surge protector. The only other 32A rated circuit that isn't marked heating or sockets is circuit 1, so that'll be a single supply running into the programmer.

That old programmer is manual switching though, it isn't smart so it doesn't know when the economy 7 tariff switches over so the immersion heaters are not separated between peak and off peak, it would normally have 2 supplies one peak and one off peak but that's no longer available. I'd guess when the meter went smart and the CU was either renewed or reconfigured, the HW controller was just bridged so both elements would always be supplied regardless. You would be advised though to get an electrician in to confirm all that.

Only way to really sort this , so it is automated, would be to get rid of the current controller and install something like the E7+ electronic programmer, that enables both elements to be controlled by one programmer that can be programmed to time switch when the tariffs change and the bottom (full cylinder heat) element can be turned on during off peak and the top element (top 1/3rd of cylinder) will be controlled via the boost function and available at all times, as it should be.

Your meter, like mine, may switch how it counts the kWh used, but it does not do any of the switching, it is up to us to program the items we have to switch on when we are on off-peak rate.

Economy 7 is an odd one out as far as off-peak tariffs go. It can change times as UTC comes in, or we return to British Summer Time. You need to check. Most of the others follow the government's time.

I have to set my immersion to heat when it is cheap, it is not automatic. Same with battery, and washing machines.

Hi all,
Thank you for your help!

I've crunched the numbers and have decided that it will actually be cheapest to switch from an economy 7 to a standard tariff since it is only the water heater that would be operating at night. This also saves having someone come out and modify the existing setup to be compatible with economy 7.

One final question I have is, for the setting on the immersion element, should I have this set to Eco?

That's actually a smart stat element

OPK setting is used with an Economy 7 setup and controller - ECO is the standard smart setting.