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Discuss E7 with 2 meters (on/off peak), but current only goes through one? in the DIY Electrical Forum area at ElectriciansForums.net

Andrew Beveridge

New EF Member
Hi folks,

We moved into a new flat about 6 months ago and have realised we're being billed for all of our electricity at the expensive "all day" rate - despite having a very large "Thermaflow" electric boiler which is designed to draw tons of power heating up water overnight to use throughout the day.

The flat has an interesting wiring setup for Economy 7 which I hadn't seen before - there are two meters (one "off-peak" / cheaper rate, one "all day" more expensive rate) and a Horstmann radio teleswitch which I believe is supposed to control the usage of the lower rate electricity.

Of the two meters, the "off-peak" one hasn't moved at all since we moved in - clearly everything is going through the all day meter.

I tried to go the sensible route to get this resolved via our supplier, but I've called them a few times and they don't seem to know anything about the teleswitch and don't seem to understand the problem at all.

Pictorial wiring diagram:
drive.google.com/file/d/1fSfQ0KYlqdu55YvD941YPKE2K0KoGAVa/view

Photo:
drive.google.com/file/d/1SvlaB1YaVGVI-cbTcr4wbCMoLfYM7Www/view

My understanding of it based on googling lots and reading is that the teleswitch (controlled by AM radio signals) is supposed to turn on and off during the night - essentially opening or closing the chunky 80A mechanical relay to allow current to flow during the off-peak times.

From my testing with the multimeter it seems like this relay is permanently closed in our teleswitch, yet no current is actually going through the off-peak meter.
I don't really understand the way this is wired up - from what I can tell it looks like all of the load (consumer unit + boiler) goes through the single Wylex main switch, which is connected directly to the live load output on both meters! As such, I don't see what would control which meter the current would flow through - I'd actually almost expect it to be split between the two, though I guess a minor variation in resistance between the two paths could cause it to pick one vs. the other.

If anybody can help me understand how it's supposed to work, and what's actually happening just now, that would be greatly appreciated!

Thanks! :)
 

spinlondon

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E7 will only work, if you have signed up for that tariff.
With 2 meters, normal stuff is powered from the day rate meter via a Consumer Unit, and heating from the E7 meter via another Consumer Unit.
In some cases, there is only one meter, but with two outputs, one to the day rate Consumer Unit and another to the night rate Consumer Unit.
Some suppliers (EON) have done away with the 2 meter system and everything is either on the day rate or the night rate.
If you are not on E7 tariff, you will have to ask to be put onto it.
 

marconi

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Your homes' electricity is indeed being supplied through the normal rate meter on the the right hand side. The problem lies beneath the Wylex switch disconnector. It has two meter supplies going into it at the top - on the left is from the right hand meter and on the right from the left hand E7 meter/teleswitch. Beneath this switch there is only one output - from the normal rate meter which goes in to the Henley block and then off to the CU and the MK thermaflow board.

To obtain E7 for the thermaflow the Henley block I just mentioned needs to be removed and then the CU fed from the left output of the disconnnector and the thermaflow from the right - but see below at ###)

Beforehand you do this you need to arrange with you energy supplier to have E7 or a similar off-peak tariff and to start receiving the radio switching signals.

Is the thermaflow only for hot water? How is space heating provided?

### When the electrician does the work ask him to uncross the feeds to the disconnector so its input and outputs match the meter positions.
 
Last edited:

Murdoch

Electrician's Arms
The answer could be very simple and that is get your E7 enabled .........

Did you change supplier when you moved in?
 

Paignton pete

Regular EF Member
deleted:

Just deleted my input due re reading original post and seeing Marconi has answered sufficiently. Sorry just got out of bed.
 
Last edited:

marconi

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http://www.thermaflowheating.co.uk/wp-content/uploads/2014/01/OFF_PEAK_CONTROL_SETTINGS.pdf

You ought to shop around for an off-peak tariff. I turned by SSE's Economy 10 tariff see page 1/2 of ref - other suppliers may have competitive tariffs which suit the electric thermaflow type wet central heating systems:

Tariff – Scottish & Southern Energy Economy 10 for wet electric central heating. Reduced rate hours as follows : 12:00am – 5:00am 1:00am – 4:00pm 8:00pm – 10:00pm
 

Andrew Beveridge

New EF Member
Thanks for the replies folks.

First, to address the points made about tariffs and how Economy 7 may work in other homes, e.g.

E7 will only work, if you have signed up for that tariff.
The answer could be very simple and that is get your E7 enabled
I know the tariff can make a difference once there's a smart meter in place (or anything else which the supplier can control really), but in our case, I'm pretty certain this isn't relevant. Here are a few additional details which lead me to that conclusion:
  1. None of the hardware (meters, teleswitch) or wiring in our home supports being controlled by the supplier.
    • The teleswitch is supposed to be controlled by the DNO (lots of further details here - we're one of only a few hundred thousand homes left with this legacy kit installed), but as mentioned above I'm pretty sure that isn't even relevant as the relay is fixed in a closed position. Presumably the current DNO (SP Energy Networks) have stopped sending out time signals to these old teleswitches already, or perhaps ours is broken.
  2. We don't have 2 CUs, or a separate "night circuit" and "day circuit". The way it's wired looks to me like both the "normal stuff" and the electric combi boiler are supposed to go through the day rate meter during the day, then switch everything to going through the night meter during the night, controlled by the teleswitch.

  3. The Thermaflow electric combi boiler provides both hot water and wet central heating - there's no gas in the property. It was deliberately designed to use off-peak electricity to heat the very large tank, with the idea being it could be heated up at any time of day which suited the supplier (controlled by teleswitch) without any noticeable inconvenience for the user.
    • The tariff which is actually best equipped to leverage this boiler and distribute load to benefit the supplier is "Economy 2000", once provided by Scottish Power, explained a bit more on this Thermaflow FAQ page. In short, that tariff is supposed to give the user 18 hours of cheap electricity per 24 hour period, interrupting the supply at times of maximum power station demand for 3×2 hour periods per day.
    • "Economy 2000" no longer exists, but the concept should work fine with Economy 7 too - ultimately, the boiler has a big enough tank that heating it up overnight should be enough to get through the full day of water+heating.
    • Once I get all this sorted out so the off-peak is actually being used, I'll certainly shop around a bit and see if there's a tariff which will save us some money. Right now though, we're spending a ridiculous amount on electricity, and the main cause of that isn't the tariff - it's the wiring, as everything is going through as peak!
  4. The supplier we're with (Ecotricity - we just moved our account with them to the new property when we moved in) only has 1 tariff, which supports Economy 7 if the existing meter/wiring setup in the home is set up for it. Our bill has info on it about both meters, knows one of them is all day / peak and the other is night / off-peak, the issue is just that the off-peak one never increases! See (redacted) image below from our most recent bill.
Ecotricity-bill-usage-summary-Q3.jpg

Next, thank you so much Marconi for actually looking at the wiring diagram and photo and offering input!

Your homes' electricity is indeed being supplied through the normal rate meter on the the right hand side. The problem lies beneath the Wylex switch disconnector. It has two meter supplies going into it at the top - on the left is from the right hand meter and on the right from the left hand E7 meter/teleswitch. Beneath this switch there is only one output - from the normal rate meter which goes in to the Henley block and then off to the CU and the MK thermaflow board.
So, the way you've explained this seems to me that I may have made a crucial, incorrect, assumption about that Wylex switch.

Because these little Henley connector blocks simply connect all inputs to all outputs:
henley-connector-block-exposed.jpg
I had assumed that the Wylex switch also did the same, so wasn't really sure what determined which of the two meters that current would flow through.

However I believe you're saying that despite there being only one on/off lever, this Wylex switch is actually acting as two switches, for two isolated circuits, which just happen to be controlled by a single physical lever?

Therefore, because everything is connected to the left side of the switch at the bottom, and nothing on the right:

wylex-main-disconnector-plus-connections.jpg

There has never been anything connected to the top right cable at all?!

:hearnoevil::electricplug::bomb: ... well, that would certainly explain why no load has ever gone through the off-peak meter!

Assuming the above is correct; thank you so much for pointing this out to me - I now know the cause of the problem is indeed wiring, and know what needs to happen to fix it.
(also, I agree with making sure the feeds are uncrossed too, for neatness as it's confusing that the left meter goes to the top right connector!)
 

marconi

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The disconnector has been labelled at the bottom to indicate the nature of the outputs.

Please resist the temptation - forgive me for suggesting this but it is very important - to do the work yourself. There are safety procedures to follow and one needs to wear appropriate Personal Protective Equipment and special tools to ensure the correct torque on the screws which a good electrician will have. It is a job for the DNO/your energy supplier.
 

Andrew Beveridge

New EF Member
Understood, thanks - don't worry, I'll leave it to a sparky. It's just good to know exactly what the problem is and what the options are for resolving it, so I can make sure the right work is done.

I've attached updated diagrams showing the current wiring vs. what the "correct" state should be if we want the boiler to go through the off-peak meter, controlled by the teleswitch - that's what I'll get a sparky to do.

As a side note, it looks like the only way to isolate that switch properly is to pull the main fuse, which in theory is supposed to only ever be touched by the DNO (not even a local sparky), and is meant to be sealed to prevent tampering.

However, ours isn't sealed:
2018-11-05 16_34_47-Photo - Google Photos.png
I guess the last sparky who was in here pulled it before doing work and didn't re-seal it afterwards. Is that something I should, in theory, try and report to the DNO?
If so, any idea how? I called SP Energy Networks previously and they said they don't deal with anything inside the home.
 

Attachments

snowhead

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The Teleswitch Radio 4 signal is still active as far as I know.

The boiler should have a permanent supply for the controls fed from the Normal rate consumer unit.
As well as the Off peak supply.
If it does have this then the system may have originally worked correctly.
If it doesn't, then it's never worked correctly.

The off peak connection has been moved out of the Isolator and onto the Henley (which was not originally in place) either because the Radioswitch / Off peak meter had failed and was awaiting repair or more likely because there is insufficient stored hot water to keep the flat warm and provide decent Domestic hot water temperature in the later day either due to size of storage or due to loss of correct Tarrif.

I doubt E.7 will be adequate to heat sufficient stored water.

It may be that it was on a timeswitch originally with E.10 or similar top up and this has been incorrectly replaced with a Teleswitch.
 

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