E7 Contactor Installation

tamste

I am on an E7 contract with Octopus with new storage heaters. When the electrician fitted the new heaters, he removed the 3 phase contactor and put everything on 24hr to avoid having to fit new 24hr feeds on the same phase as the heaters. Charging period is currently controlled at the heater level which works fine, but doesn't comply with Octopus's requirements for the Snug tariff, as they need to control the charging through a contactor.

To get onto Snug Octopus, which I would like to do, I would thus need the contactor replacing and a bit of work in reconfiguring the 24hr plug circuits so that a 24hr supply on the same phase as the contactor circuit is available next to the heaters, permitting use of charging through the contactor. Currently L1 is all normal 24hr circuits with L2 and L3 for storage heaters only, though I am considering moving the key storage heaters onto one phase as these are in a part of the house where the 24hr sockets could be changed with a new distribution board.

Who supplies and fits the contactors? Is this a job for my local electrician, or would this need to be done by Octopus? Not talked to sparky yet regarding this, .. just want to be informed before I set the wheels in motion for this in a couple of months.

No1_Anorak

It's quite unusual to have a three phase supply in a domestic environment to start with?

Anyway in my case we have an all electric house [as we made the conscious decision to do that as we didn't want a gas boiler any longer] plus we were having solar+battery installation and like you we also had a modern storage heater type set-up installed.

I'm not exactly sure how your heaters will be easily split off from your normal ring main but in our case it was just a case of having a new meter installed [in our case Economy 10] and the meter has a built in contactor that only makes the heating circuit live at the off-peak periods [Economy 10 off-peak times are 00:00-05:00, 13:00-16:00 and 20:00-22:00]

And before anyone starts saying anything about the meter situation, our Economy 10 meter is a latest generation digital meter that is not reliant on the RTS signal that is being switched off [that old type Economy 7 and 10 meters needed to control the peak/off-peak]

Rodders53

This will be for you/your electrician to supply and fit. Your last one did you a big disservice by removing the old one rather than wiring in a second supply to each storage heater (although it'd have cost more).

Do though compare the savings in electric to be made via Snug cf any other E7 tariff that Octopus (and other suppliers) offer… based on your own electric consumption records for heating the home.

Factor those leccy savings against the capital outlay for the new wiring and a payback period.

tamste

Thanks for the responses.

We are an all electric house and took the decision to replace the >30 yr old storage heaters rather than plumb in a full wet system to go with ASHP. Not looked back as the system works just fine.

The company who installed the solar and heaters used a contractor for the installation, and I didn't know he was going to take out the contactor. All I said is that I didn't want surface fitment or the walls channeling to fit a phase compliant supply to each heater. This is how I ended up with everything on the 24hr supply, programmed at heater level. This was not a big concern at the time (15 months ago), but I am looking to change tariff in a couple of months, setting up for ready for next winter. Snug is the best choice for me at the moment, but as a smart tariff, Octopus need to control when the heaters charge, thus a contactor is required. No intention of getting an EV.

After comparing a range of E7 tariffs, Snug works out best for us by a long way due to the 9p kWh TOU rate vs ~13p/kWh for basic E7 tariffs. We import ~18,000 kWh annually with ~75% at off peak, thus the off peak rate for us is critical. Luckily, with 11.44 kWh of solar we tend to halve the total bill at the 15p kWh export rate (hoping it will remain). Battery wouldn't work for us at the moment as ROI would be in the region of 10 years, but with ~90% of out total heating collected at off peak, we are storing the energy anyway.

So rewiring the circuits close to the main heaters to the same phase is my latest thought on how to overcome this and make us eligible for the Snug tariff.

Overall I would need to move one storage heater from L3 to L2 (consumer units next to each other), and one 24 hour supply plug circuit from one of the consumer units to the other .. both currently on L1, but change one to L2. Easy access for all work as it is all in an attached garage if my plan works, so hoping ~ half a days work?

QrizB

I'dbe tempted to look into whether you can use some sort of wireless system - ZigBee switches, perhaps - to allow the contactor to switch your storage heaters without needing any wider messing about with your supplies.

You'll probably still need the contactor fitting, though.

tamste

Not sure how a wireless system will help??? .. can you please explain.

Not sure if Octopus can see the contactor without a physical inspection(?), which might make the proposed work a waste of time and money if they can't, but just trying to be compliant with their T&C's.

My storage heaters need either a single 24 hour supply, or a switched charging (E7) supply and a 24hr supply for the fan and controls. As I understand it, if both supplies, they must be on the same phase, thus the proposal to change the distribution boards around a bit.

WiserMiser

If you're using a 24h supply with a local timeswitch to mimic the E7 switching times, make sure you have a switched outlet with a neon indicator somewhere that can be seen at a glance.

Many people use the nominal switching times for their region and don't realise they're starting to charge at the E7 day rate which is even more expensive than the standard rate.

Similarly, don't use a mechanical (rotary) timer because power cuts can disrupt the schedule and make the running costs prohibitively expensive.

tamste

The storage heaters have their own individual charging control, set correctly to the regional E7 start time and duration. No need for local time switches etc.as everything is integral to the heater. I was trying to do the right thing in getting new efficient HHR heaters, which to be fair, are very good.

Problem I have is my installation which isn't compliant with the terms for the tariff in that Octopus cannot control when the heaters start and finish charging. I can control it, but they can't, so outside of "smart" tariff terms.

Hoping the rather "minimal" changes I am proposing aren't going to be too costly to implement.

WiserMiser

https://forums.moneysavingexpert.com/discussion/comment/81882240#Comment_81882240

"The storage heaters have their own individual charging control, set correctly to the regional E7 start time and duration."

The problem is that your meter will have a fixed offset. If the regional start time is 2230 but your meter happens to start at 2245 then the first 15 minutes of charging will be at the very expensive E7 day rate. 😱

Forget the published times, look at your meter and watch it as it switches over. That's the only way to be sure.

If the cheap rate in your region has a gap in the middle (e.g. 2230-0030 and 0230-0730) then there could be another expensive 15-minute charge in the middle of the night.

"No need for local time switches etc. as everything is integral to the heater."

It's still a local timeswitch, even if you're just programming its internal controller. It doesn't know what the REAL switching times are.

tamste

The real switching times are bang on in my location.. watched them switch over several times over the last 18 months, both prior to the new heaters, and since. Thank you, but this seems a little off topic to the original query.. 🙄

Ildhund

@tamste wrote:

The real switching times are bang on in my location

What make and model of meter is this? SMETS2 requires meters to apply a 'randomized offset' of between 0 and 1799 seconds to delay the switching times for ToU systems like Economy 7. I wonder just how close 'bang on' is in this situation.

The nominal times are agreed between supplier and generators, so it's not just location that dictates them.