3-phase E7 meter on single phase supply?

(1) No reason why you cannot use two phases of a three-phase meter - think of it as a three-phase installation with one phase drawing no current. The problem is, however, that EON seems to require a smart meter. If it isn't a smart meter, how would it be possible to know when the electricity was used?


(2) Just because the fuse-holders are rated at 100 A doesn't mean that 100 A fuses are fitted. They may be only 63 A. If you "upgrade" to a single 100 fuse, you need to be sure that the wiring downstream will cope. That's where the electrician comes in.


By the way, when did you last get the installation inspected and tested?

The supervisor suggested that a 3-phase meter could be fitted retaining the two fuses and the meter is then fed by two cables although it is still a single phase supply.

That sounds dodgy to me - with two 100A supplies sharing one N as it passes through the meter etc. the N could be carrying anything up to 200A nominal. It could perhaps be 'made to work' with some very careful layout (usually N doesn't have to go through the meter) but it doesn't seem like an ideal solution to me. Everything on a single 100A fuse would be much simpler and more usual.


Two separate meters was common enough on old E10/E12 systems - the tariffs were different and everything on the "normal" circuits was charged at the higher rate regardless of the time of day - so they often had two ordinary meters rather than one dual-rate meter.


   - Andy.

2 fuses like that  is more like you'd expect if the building had been divided into flats or one of them is next door's meter.

I cannot really see that you need more than one supply and a normal E7 meter. Is this an ordinary house or some enormous mansion.

Do the 2 meters share an MPAN number and do you pay 2 lots of standing charges ?



(The Meter Point Administration Number (MPAN) is used to identify individual electricity supply points. It's usually a 21-digit number with the letter 'S' at the beginning and is displayed in a grid.
)

I was involved in a conversation with two DNO engineers who had the district manager on the phone as well and they all agreed that a single phase supply cannot be run through a three phase meter for metering purposes. You don't even want two phases, they are the same phase being metered separately, but a three phase meter only gives one reading.


Is there any reason you cannot just keep the existing tariff? It sounds like you may do yourself down by changing tariff and doing nothing is the best option.


But those fuse holders may have 60 or 80 amp fuses in them rather than 100 amp and you may be overloading the supply with all the heaters you want, with the expenditure presumably in the region of four to five thousand pounds central heating has to be a viable alternative.

One of the features of smart meters is that they are supposed to be enable suppliers to offer complex tariffs, something is not quite working as it should!


Without a separate off-peak meter you would be running appliances of the daytime reduced rates, well actually you could be anyway ?, the truth is they want to ensure you pay the highest rates during the day.

Chris Pearson: Good point about the fuse rating - I had assumed that because the fuse holder stated 100A then that was the fuse rating.


I've never had the installation inspected or tested and don't know anyone who has? The building is modern built about 1990 and both Consumer Units have MCB with RCD protection. I've lived here about 20 years and don't get any tripping apart from once when immersion element failed and gave earth fault. I have been thinking of moving and intend getting the installation tested and a safety certificate issued to offer when property is for sale just as I will get chimney swept and a certificate that flue is ok. Not a legal requrement but helps sale.

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AJJewsbury: Thanks for that - yes, the normal meter is same rate at night unlike E7

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mapj1: The building is a modern small detached bungalow built about 1990 with modern wiring.  Thanks for info but I can't see MPAN number but yes, I pay standing charge on both meters.

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Sparkingchip: Thanks for info on 3-phase. EON say I can't keep the tariff I'm on as it is discontinued. Yes, understood about fuse rating but my calc of about 70 amps max does assume all heaters and immersion are on load continuously for 7 hours which I undestand is the correct assumption to make but in practice they won't be so 80A fuse would probably be ok.? I don't want to install a wet CH system, I think the future is electric and provided by renewables. Low maintenance and no servicing. A friend of mine has just upgraded to Dimplex XLE and they are still giving out heat when he goes to bed so he's really pleased with them

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Simon Barker: Yes, I suggested that the one fuse be removed and the new E7 meter be supplied by the existing single-phase through one fuse but was told they would not do that. Point taken about cost of electricity  but the 70A would not be drawn for the full 7 hours so not sure what cost wil be. I currently pay £600 per year for coal which is only used for about 20 weeks.

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Finally, a big thank you for all the comments, advice and suggestions  and I've just has some good news. The supervisor who I spoke to on the phone has just phoned and he has spoken to his manager. He has retracted the suggestion of a 3-phase meter as they now don't think that would work! They have agreed to fit a new E7 Smart Meter supplied by the existing incoming single-phase cable through one of the board fuses. He agrees with you guys that it may not be a 100A fuse as I had assumed but I can get that upgraded by Western Power if needed.


One final question out of interest about the incoming supply cable - what is the current rating of that? It measures about 15mm dia.

Thanks - Nigel

I suspect E7 3-phase smart meters are as rare as hen's teeth.


Well, I'll find out on Mon 12th between noon and 4pm as EDF wanted to install a smart meter. I have advised them of my existing set up and asked if it were possible and I was told it is....... I'm not convinced...... The "adviser" even asked it it fed a dedicated "off-peak" CU so had some awareness.

Also, it will be interesting to see if it can't be installed, whether I get the clause 7 £30 in the appointment letter for a no show appointment for wasting my time.... Again, I doubt it!


Regards


BOD