Night tariff times changing, how to adjust times my storage heaters switch on/off?

[Rich05uk]

Hi All,

I'm new to this forum but joined as it says its the UKs friendliest electrical forum and I'm after some friendly assistance.

I've just moved house and it has 10x storage heaters and 2x hot water cylinders with each containing two immersion heaters, presumably one is on the night circuit and the other on the day.

I'm due to move onto Intelligent Octopus Go tariff as I've got an EV and it's costing me a fortune, even if charging at the night rate, the new tariff halves my night rate to 7p per kWh. However it also means my night tariff changes from being active between 00:30 - 07:30 to being active between 23:30 - 05:30.

I've got a 3-phase supply with a dual tariff meter, it's not a Smart Meter but this is due to be changed on the 2nd Jan to a 3 phase smart meter. I've been told by octopus that my supply currently switches between the night and day tariffs at set times and the whole house benefits from the night time tariff when it switches over. There doesn't appear to be a separate night circuit coming from the meter to power the storage heaters when the meter switches over to the night tariff as I've had in the past, years ago when I lived in another property with storage heating.

How are my storage heaters and immersion heaters switched on/off at the correct times to align with the night tariff times if this is not done by the meter?

I've been trying to figure out the Electrical installation as a whole and it's confusing for me, I'm used to a single phase supply and 1 consumer unit. This house has 3 phase and has all kinds of electrical 'boxes' dotted about the property and I've so far uncovered 5 different consumer units which are also dotted about the property.

The previous owners are in their late 70s and are confused by my questions. They said they had the hot water systems installed in 2023 when they had the property converted to 3 phase as they kept overloading the single phase circuit. They also have had much of the house rewired in stages in 2020, 2021 and 2022. Despite this the only certificates they can provide are pre 2023, each certificate uses a different electrician so don't know if this is bad for continuity or it might not matter, but all of the provided certificates relate to work when the property was still single phase. I've contacted each of the electricians on the certificates but they each tell me they aren't qualified for 3 phase and so can't help me. I would really like to find the electrician who converted the property to 3 phase so I can ask them to walk me through the installation and tell me what is connected to each circuit and which circuits are on the switch night tariff and which are not.

Anyway, I've taken some photos if anyone can offer some advice or share some of their wisdom with me, I'd appreciate your help.





















What is a surge suppressor, which circuits are covered by this and why is it needed here but not in any of the other consumer units?

You'll see in the following photos that I found another consumer unit in the roof space, along with a metal box on the left and a big plastic box to the right of it, the consumer unit in the centre contains an analogue MODT180 (16A, 24Hour ON/OFF Mechanical Timer) and based on this, plus the labelling in here, I'm guessing it might be the answer. I'm not sure how I can confirm this switches all the storage heaters or not and if it also switched the night immersion heaters in each of the 2 tanks or not?








Also, how do I change the times on this, can it be done easily without taking the consumer unit apart, can I do it or do I need an electrician to come on to do it? Its tricky to get to and on my hands and knees in the loft, I couldn't easily play around with this to see how it could be adjusted, especially as I don't know if this can be done by the home owner such as myself, or if it needs dismantling somehow by a qualified electrician to change the switching times?

It's also only rated 16A so doubt it can be switching all the storage heating and immersion heaters directly. But at the same time, I don't know what the contactor switch next to this is for, could the MODT180 be controlling a remote/ relay switch in one of these boxes at the side that then switches all the storage and immersion heater circuits?

Downstairs in an outside toilet, which is adjacent to the meter, I've also found a big metal box which has a switch on the front, all the wires coming from the meter go into here first before going off elsewhere, what's this for?



You can see the meter is relatively new and has the 4 cables (N, L1, L2 and L3) running through it for the 3 phases.



Any help much appreciated.

Thanks,

Richard.

 

[Fleeting]

Picture 3 looks like your night tariff consumer unit. The supply for this almost certainly comes from picture 6 and is controlled for night operation by way of a time clock which switches a contactor to power the night tariff consumer unit. I suspect that night tariff consumer unit has a three phase, 400v supply. That consumer unit would not be rated for 400v.

 

[Murdoch]

It’s very hard to give advice from this information and pictures - you really need somebody on-site to conduct a thorough EICR

You appear to have 37 + circuits so identifying all these will take time

If you have an EV point, which board is it attached to?

 

[binky]

that timer is like other mechanical plug in timers you may have had in your house, you move the blue segments to set on and off times. Have a look for user manual on line. No need to open the board to adjust the segments, just lift the flap, and turn the wheel round by hand (dont try to force it backwards).

the big switch with the meter tails is just an isolator, probably with fuses in the box, ie cuts off entire supply to the house. Seems a bit surplus to requirement given the other isolator in the meter cupboard, but we fit switch fused isolators when the meter tail run exceeds 3 m, ie we treat it as a submain. Given that the meter tails run from downstairs toilet to attic, can't help feeling that should have been an armoured cable rather than meter tails

so basically you have single phase boards around the house, no doubt fed from different phases off the 3 phase head. I very much doubt any of the equipment is actually 3 phase, and can't help thinking a 2 phase supply might have sufficed for the extra loading, but 3 phase obviously gives greater flexibility. The board with multiple main switches probably have multiple phases in them ie part of the board is phase 1, part of it phase 2 etc.

One thing you may consider is getting air source heat pump, it would almost certainly be far chepaer to run than NSH as it gives around 3 to1 heat ratio. ie if you put 1 kw in, you get 3 kw of heat out.

And welcome to the forum. We are mostly friendly, except to those who claim to be electricans but clearly havn't got a clue about basic electrical theory and practice, yet are charging the public money....

 

[michael8554]

For obvious reasons the electricity supplier would not let you control when the Off Peak switches occur.

That mechanical switch you can alter might be supplied from the real Off Peak switch, and would allow you to set the times for whatever that switch is attached to.

In my house with Economy 10 and storage rads there is a sealed mechanical clock, set to the three Off-Peak times by the supplier.

And that switches a big contactor that powers the rads during Off Peak periods.

 

[binky]

For obvious reasons the electricity supplier would not let you control when the Off Peak switches occur.

That mechanical switch you can alter might be supplied from the real Off Peak switch, and would allow you to set the times for whatever that switch is attached to.

In my house with Economy 10 and storage rads there is a sealed mechanical clock, set to the three Off-Peak times by the supplier.

And that switches a big contactor that powers the rads during Off Peak periods.

The days of separate off peak metering controlled via a signal broadcast over Radio 4 wavelength are long gone. Most off peak is via dual tariff meters these days, and it's up to to you to turn devices on and off at off peak times.

 

[ProDave]

In the "old days" the supplier controlled the switching of storage heaters, originally with a time clock separate to the dual rate meter, then more recently a dual rate meter with a switched output that was only on at off peak times.

I don't think that has ever been available with 3 phase.

Your meter might have a pilot output that could be used to switch a contactor, but if it has, that is not being used, and in any event when you swap to a smart meter it won't have that.

That little time switch probably does switch your storage heaters. Try it. There should be a manual on / off switch on it, or if not just advance the dial manually to the middle of the night. You should hear a loud clonk when the contactor energises, it might be in that plastic box to the right of the board with the time switch.

If it works, you hear a clonk when you turn it to the middle of the night, and you should also see your usage start to increase quickly as all the storage heaters start to charge up. If so then all you need to do is adjust the on off times to suit your new off peak times when you get your new meter and switch to your new tariff.

Here is an enlarged view f that time switch



The little blue switch bottom right is in the "timed" position. Push it down and it is always on, so do that in the daytime and you should hear the contactor turn in with a clonk. Switch it up to the off position and you should hear it clonk off again.

the current time is shown by the little arrow just above the switch so when that picture was taken it was about 12 mid day.

The blue segments pushed to the left are "off" and the blue segments pushed to the right are "on" So you want all the segments in the off peak time period pushed to the right.

When adjusting the time or the on off period, only rotate the "drum" by pushing it upwards, it's like a lot of clocks, they don't want you to push it backwards.

 

[Rich05uk]

Thanks everyone for the replies, its really helpful and I appreciate all the advice.

For the record, yes I intend to get an electrician to come in to survey the whole installation, I only moved in on the 16th Dec and switched to Octopus on the 23rd and then requested a 3-phase smart meter which they said wouldn't be before April, so I though I had plenty of time to sort this out but Octopus called me on the 27th to offer an earlier appointment on the 2nd Jan (I will say I am always impressed by Octopus Energy Customer Service), so I now need an immediate way forward to avoid an expensive bill with the NSH's charging for an hour or two at the standard tariff. I am still hoping to get the name of the contractor who installed/converted the property to 3-phase back in 2023 but I don't have any details currently, the previous owners only communicate via snail mail and so I'm waiting for their reply with who this might have been.

But, I am happy to phone around some other electricians (if any here who coverers Cornwall, St Austell area, please let me know) to take a look at this, what should I ask for, a full EICR for a 3 phase property or is there some other type of survey I should be requesting from them?

Picture 3 looks like your night tariff consumer unit. The supply for this almost certainly comes from picture 6 and is controlled for night operation by way of a time clock which switches a contactor to power the night tariff consumer unit. I suspect that night tariff consumer unit has a three phase, 400v supply. That consumer unit would not be rated for 400v.

Thanks Fleeting, this makes a lot of sense, looks I need to figure out which bedroom is which as its not clear from the labelling but that should be easy enough. I am still not sure how the immersion heaters are wired though, I have 2 tanks each with 2 heaters (4 heaters in total) so assume the one heater at the bottom of each tank should be the one that switches on during off-peak and the other heater at the top of each tank is on 24x7?

The consumer unit in picture 3 (assumed to be the off-peak/night consumer unit) only has 1 circuit labelled immersion, could both night immersion heaters (one in each tank) be wired to the same circuit/switch)?

Picture 1 has 2 circuits labelled immersion top and immersion bottom, so assume as one tank is ground floor and the other is upstairs, this will be to the two 24x7 immersion heaters located at the top of each tank?

Not sure therefore what the switch labelled Immersion DB5 in consumer unit shown in picture 2 relates to this? It suggests there is another consumer unit or similar, called DB5, but I can't (yet) find this anywhere?

It’s very hard to give advice from this information and pictures - you really need somebody on-site to conduct a thorough EICR

You appear to have 37 + circuits so identifying all these will take time

If you have an EV point, which board is it attached to?

Thanks Murdoch, yes I appreciate that and suspected this would be the case. I hope to find the original contractor who installed/converted the 3-phase, so I can have them complete this survey / EICR as I assume it would be easier/quicker for them to identify everything if they remember what they did, it was done in 2023 so not too long ago.

I am currently only charging from a granny charger from a 3-pin socket in the garage, if programmed the car to charge at 6A only for now, until I can get an electrician to confirm the wiring can accept the usual 10A from the granny charger, but ultimately I do want a normal EV charger installing, in fact I need 2 as my other half will be changing her car soon to be an EV, this is where I think the 3-phase will come in handy. I also hope to get solar, battery and ASHP down the line, I've already had a solar installer saying I can fill my garden with solar panels because my house is on 3-phase, I can apparently triple the limit of solar my property is permitted to have (I think he stated 60+ panels) and consequently, would earn a decent figure from exporting to the grid, not sure I want to fill my garden with panels however.

that timer is like other mechanical plug in timers you may have had in your house, you move the blue segments to set on and off times. Have a look for user manual on line. No need to open the board to adjust the segments, just lift the flap, and turn the wheel round by hand (dont try to force it backwards).

the big switch with the meter tails is just an isolator, probably with fuses in the box, ie cuts off entire supply to the house. Seems a bit surplus to requirement given the other isolator in the meter cupboard, but we fit switch fused isolators when the meter tail run exceeds 3 m, ie we treat it as a submain. Given that the meter tails run from downstairs toilet to attic, can't help feeling that should have been an armoured cable rather than meter tails

so basically you have single phase boards around the house, no doubt fed from different phases off the 3 phase head. I very much doubt any of the equipment is actually 3 phase, and can't help thinking a 2 phase supply might have sufficed for the extra loading, but 3 phase obviously gives greater flexibility. The board with multiple main switches probably have multiple phases in them ie part of the board is phase 1, part of it phase 2 etc.

One thing you may consider is getting air source heat pump, it would almost certainly be far chepaer to run than NSH as it gives around 3 to1 heat ratio. ie if you put 1 kw in, you get 3 kw of heat out.

And welcome to the forum. We are mostly friendly, except to those who claim to be electricans but clearly havn't got a clue about basic electrical theory and practice, yet are charging the public money....

Thanks blinky, and thanks for the welcome. I am familiar with this style of timer but wasn't sure how to access this particular type to change it, so that plastic cover you think should just lift up by hand?

Should the run from the meter to the isolator switch, and then from the isolator switch to the attic all be in armoured cabling, and if so, what are the implications of it not being armoured, is it non-confirmative / illegal? Should this have been registered with building control at the time or with some other organisation so I can check for compliance?

I agree with getting air source heat pump, the property is quite old impossable to insulate any more without significant cost to re-build all the external walls, some installers say there would be no benefit but I beleive through research online that this infomration is now considered outdated. For me its simple, the heat loss is the same weather heated by NSH or by ASHP and so if I can improve the efficiency of the heating from 1:1 to 1:3 then it will be a saving, irrespective of how poorly my property is insulated.

For obvious reasons the electricity supplier would not let you control when the Off Peak switches occur.

That mechanical switch you can alter might be supplied from the real Off Peak switch, and would allow you to set the times for whatever that switch is attached to.

In my house with Economy 10 and storage rads there is a sealed mechanical clock, set to the three Off-Peak times by the supplier.

And that switches a big contactor that powers the rads during Off Peak periods.

Thanks michael8554, yes this is what I am used to but my meter simply switches the entire property from tariff 1 (peak/day) to tariff 2 (off-peak/night) at 00:30 and then switches back to tariff 1 at 07:30. I have seperate meter readings for each tariff. Therefore in my situation, the switching of equipment to come on during the off-peak hours is not performed by the meter itself, but elsewhere such as by this MODT180 switch.


Thanks again everyone, and please continue to post any further ideas to my above queries should anything spring to mind.


Cheers, Richard.

 

[Rich05uk]

In the "old days" the supplier controlled the switching of storage heaters, originally with a time clock separate to the dual rate meter, then more recently a dual rate meter with a switched output that was only on at off peak times.

I don't think that has ever been available with 3 phase.

Your meter might have a pilot output that could be used to switch a contactor, but if it has, that is not being used, and in any event when you swap to a smart meter it won't have that.

That little time switch probably does switch your storage heaters. Try it. There should be a manual on / off switch on it, or if not just advance the dial manually to the middle of the night. You should hear a loud clonk when the contactor energises, it might be in that plastic box to the right of the board with the time switch.

If it works, you hear a clonk when you turn it to the middle of the night, and you should also see your usage start to increase quickly as all the storage heaters start to charge up. If so then all you need to do is adjust the on off times to suit your new off peak times when you get your new meter and switch to your new tariff.

Here is an enlarged view f that time switch

View attachment 17473

The little blue switch bottom right is in the "timed" position. Push it down and it is always on, so do that in the daytime and you should hear the contactor turn in with a clonk. Switch it up to the off position and you should hear it clonk off again.

the current time is shown by the little arrow just above the switch so when that picture was taken it was about 12 mid day.

The blue segments pushed to the left are "off" and the blue segments pushed to the right are "on" So you want all the segments in the off peak time period pushed to the right.

When adjusting the time or the on off period, only rotate the "drum" by pushing it upwards, it's like a lot of clocks, they don't want you to push it backwards.

Thanks ProDave, this is perfect, so long as I can just lift up that little flap to access it, then I am confident I can update the timings for the storage and immersion heaters to come on during the new off-peak times, I will do this tomorrow once the new meter is installed as its a bit awkward working my way to the far end of the loft to access it, not sure why it was put there as its the farthest point from the access door into the eves space. Thanks again for confirming which way to rotate the clock too as this was another uncertainty I had. While I'm there I will certainly try to manually switch on/off the circuit and listen out for that clunk, I can then hopefully identify if its coming from the plastic bot to the right or the metal box to the left.

 

[binky]

Thanks blinky, and thanks for the welcome. I am familiar with this style of timer but wasn't sure how to access this particular type to change it, so that plastic cover you think should just lift up by hand?

yep just lift up.

Should the run from the meter to the isolator switch, and then from the isolator switch to the attic all be in armoured cabling, and if so, what are the implications of it not being armoured, is it non-confirmative / illegal? Should this have been registered with building control at the time or with some other organisation so I can check for compliance?

depends really on whether the cable could get damaged. Meter tails are 'singles' in that they have no built in earth, so its possible to cut one without hitting the earth cable and tripping any protective device, ie a fuse or MCB. I wouldn't describe it as illegal, just safer as an armoured cable or other cable containing an earth. Any works like this should have been registered with building control., but it looks like a reasonably tidy job.

I agree with getting air source heat pump, the property is quite old impossable to insulate any more without significant cost to re-build all the external walls, some installers say there would be no benefit but I beleive through research online that this infomration is now considered outdated. For me its simple, the heat loss is the same weather heated by NSH or by ASHP and so if I can improve the efficiency of the heating from 1:1 to 1:3 then it will be a saving, irrespective of how poorly my property is insulated.

I have a victorian terrace house, fitting insulation is an expensive job, and I'm not convinced it's actually good for the building. My house was designed to 'breathe' and not be sealed up.

 

[UNG]

For obvious reasons the electricity supplier would not let you control when the Off Peak switches occur.

That mechanical switch you can alter might be supplied from the real Off Peak switch, and would allow you to set the times for whatever that switch is attached to.

In my house with Economy 10 and storage rads there is a sealed mechanical clock, set to the three Off-Peak times by the supplier.

And that switches a big contactor that powers the rads during Off Peak periods.

There are many different ways that the off peak electricity tariff has been switched over the years, the time switch like you have, the meter that has has a switch for the off peak that energises a separate output or the radio tele switch (RTS) system which is closing down towards the end of June 2025 to name a few
Originally the Economy 7 tariff was for storage heating only but over the years the off peak tariff has changed and now with multi tariff meters the whole property is switched to off peak by the meter which puts the responsibility on the end user to set the switching times for the off peak electricity using equipment

 

[UNG]

In the "old days" the supplier controlled the switching of storage heaters, originally with a time clock separate to the dual rate meter, then more recently a dual rate meter with a switched output that was only on at off peak times.

I don't think that has ever been available with 3 phase.

I have worked on numerous three phase commercial storage heating installations since the late 70's some operated by the suppliers time switch and a contactor and others using customers controls back then a company called Pactrol produced a charge optimisation controller for storage heater systems that regulated the amount of time needed to heat the storage heaters based on the indoor and outdoor temperatures, it worked well in the warmer months rather than someone manually adjusting or turning off the heaters and then not reverting the previous settings as the colder months kicked in

Had one about 8 - 9 years ago was asked to do an EICR on a commercial premises and went for a look round in the mains cupboard they had a small consumer unit and 2 three phase boards I was told one of the three phase boards didn't have power so it didn't need to be included, after pressing the override on the sangamo time switch and a quick check to confirm it was switching I pointed out that the contactor below the board was faulty after a few questions I found out that they had moved some of the storage heaters to the peak board, I ended up replacing the contactor and reconnected the heaters to the off peak board a few months later I got a call querying why a couple of couple of guy's from the electricity supplier would come calling and snooping around, I pointed out that having got the off peak board working the load profile would have significantly changed across the peak and off peak readings and it was likely they were revenue protection checking they weren't fiddling the meters