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3-phase E7 meter on single phase supply?

Former Community Member
Former Community Member
My home is wired for storage heaters but none are fitted at the moment. I’ve been using a multi-fuel stove using mostly coal but I have decided to have storage heaters fitted for this winter. I have been with EON on their Heatwise tariff which gives off-peak hours 5 at night; 3 in afternoon and two in evening.. I have two consumer units  - one for normal rate and one for off-peak rate with only the immersion heater using off-peak at the moment.
EON have told me that I can’t have this old tariff anymore and so I agreed to move to their E7 tariff and have an E7 Smart Meter installed.
I currently have a single-phase incoming supply cable feeding two 100A fuses and two meters. One fuse feeds a normal rate meter and the other fuse feeds the off-peak meter. I don’t know why there are two meters fed by separate fuses and why the installation does not use the off-peak meter to record normal rate usage.
I discovered that the meter technician is not a qualified electrician and he didn’t know what to do so he phoned his supervisor who told him not to proceed with the meter change. I spoke to the supervisor on the phone and asked him why the one fuse cannot be removed and the remaining fuse can then supply the new E7 meter. He told me that I would have to get a qualified electrician to approve that which surprised me and I got the impression that these meter technicians don’t appear to know an awful lot.
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. He also told me that the 3-phase meter would not be a Smart Meter. The meter technician was not qualified to do that but he could do the job himself so would phone me later to arrange it.
Another thing the supervisor told me was that I could only have four night storage heaters which I disagreed with explaining that I was proposing to have five which would add up to 17.22kw including the 3kw immersion element – equating to just over 70A and surely the limit is the total load and not the number? There is no electric shower fitted.
I don’t have a lot of confidence that these meter technicians know what they are doing and would have preferred a qualified electrician but EON don’t have any to do meter changes.

My question is does this sound ok or not please – can a 3-phase meter be fitted and fed by two cables from the incoming single-phase supply through the two fuses already fitted.  This all sounds a bit strange so any help appreciated so thanks for any comments.
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  • Former Community Member
    0 Former Community Member
    No I didn't Chris. Not sure why. Regards. BOD
  • 0
    I installed two Dimplex HHR heaters and the cost was just shy of two thousand pounds, I have just got another quote for the new upgraded version which are WiFi connectable, but you need a hub.


    So the new quote for two Dimplex HHR heaters and a hub is now over £2000, but you don’t have to have the hub as they are individually programmable, that will get it back below 2K, however then there’s the fitting as they need assembly and connecting to two supplies.


    If you want a decent Energy Performance Certificate rating they must be HHR High Heat Retention heaters, so that is what you need if you are going to rent the property to a tenant and really if that’s what you need for a tenant then you are doing yourself down by not installing to the same specification.


    Five HHR heaters with a hub and installation can easily be pushing 4K to over 5K, so takes a bit of thinking about.


     Andy Betteridge.
  • 0
    I should point out that the EPC rating is purely based on running costs, not about saving polar bears.


    So most EPC assessors  would tell you to install gas central heating and not to touch an air source heat pump with a barge pole.


     Andy B.
  • 0
    Would it be to much to presume they could install two Smart meters side by side interconnected with Zigbee WiFi allowing just one of the meters to forward the information from both to the supplier?
  • 0
    Sparkingchip:

    Would it be to much to presume they could install two Smart meters side by side interconnected with Zigbee WiFi allowing just one of the meters to forward the information from both to the supplier?


    Probably. Apparently the system can't cope with having an extra smart meter to independently measure the the total generation from PV panels - so I doubt they could do anything as useful as pairing two together. Remember these are the people who originally couldn't anticipate consumers in the UK market switching suppliers.

       - Andy.


  • 0
    Rumour has it the suppliers were not invited to take part in the design process with the government thinking they knew best.
  • 0
    Sparkingchip:

    ... with the government thinking they knew best.


    Never! ???


  • 0
    Economy 7 gives you the whole supply at the low rate during the low period as well as providing a switched low rate supply for storage and water heating.  Your current (old) arrangement is effectively two supplies so the lower rate only applies to the switched supply.  Has  the withdrawal of this old arrangement been triggered by a request from you or have E.on done this independently?  If the former you could press them hard to retain the existing setup as the afternoon charge will help maintain temperatures.  You existing arrangement will probabaly have two MPANs and if you want Smart meter they can always fit two Smart Meters.


  • 0
    Given it is as you say " a modern small detached bungalow built about 1990 with modern wiring.  "

    So presumably insulated cavity walls, loft insulation, double glazing, porches on outside doors  etc.

    I'd be a bit surprised if it really needed 70A amps worth of heating to be honest, unless there is a big hole in the roof or a swimming pool or some other hard to heat feature like that which you have failed to mention.  Yes if you fitted a gas boiler it would be 18 to 24 kW for a non combi, and larger if you wanted a combi to give instant hot water, but then it would be off most of the time until you run a bath.

    Has the 17kW design been done by someone allowing for the thermal envelope of the house ? I suspect that half that may be enough in practice.
  • 0
    Dont forget that you are only charging for 7 hours and then that spreads out over 18 to 24 hours so the 70A will effectively be 24 to 35 average if you take that into consideration

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