Nick1c Posted October 9, 2018 Share Posted October 9, 2018 The house we will be demolishing has economy 7. I am not sure if this is the reason for it, but there are two overhead cables into the house, I have talked to the power company about running a builders supply to the bottom of the pole and they are keen to reduce this to a single supply [something about room in the box]. Is there any benefit to keeping the two cables? I am aiming for a pretty thermally efficient build and may use an ASHP. Link to comment Share on other sites More sharing options...
ProDave Posted October 9, 2018 Share Posted October 9, 2018 Even with economy 7 you only need 1 cable into the house. Do you have two separate supply heads, two meters and two MPAN's? If so you will be paying 2 lots of standing charges. Was the house ever 2 houses now joined into one? Link to comment Share on other sites More sharing options...
dpmiller Posted October 9, 2018 Share Posted October 9, 2018 are the two wires just Live and Neutral maybe? Link to comment Share on other sites More sharing options...
ProDave Posted October 9, 2018 Share Posted October 9, 2018 6 minutes ago, dpmiller said: are the two wires just Live and Neutral maybe? OP needs to explain better, with a photo if possible. Link to comment Share on other sites More sharing options...
Nick1c Posted October 10, 2018 Author Share Posted October 10, 2018 Western power were talking about a dual supply, my architect about 2 phase ( which I don't know exists, I have just heard of 'normal' & 3 phase). Pic below. Link to comment Share on other sites More sharing options...
Triassic Posted October 10, 2018 Share Posted October 10, 2018 (edited) We have two overhead wires but only one 240v supply. I’m sure the overhead wires are live and neutral. Edited October 10, 2018 by Triassic Link to comment Share on other sites More sharing options...
ProDave Posted October 10, 2018 Share Posted October 10, 2018 And the smaller cable to the right is your telephone cable. Link to comment Share on other sites More sharing options...
Temp Posted October 10, 2018 Share Posted October 10, 2018 How much current (Amps) can they give you on one phase? If you are planning an all electric house (ASHP, multiple showers, electric car charging point?) then check they can give you enough. Link to comment Share on other sites More sharing options...
Ferdinand Posted October 10, 2018 Share Posted October 10, 2018 It could be a benefit later were you to want separate meters eg if you were to plan to rent out an annexe or sell off a garden building plot. In thse circs it could be worth several thousand as a saving. Presumably whilst they exist, one can be run on a zero-Standing-Charge tariff if not used so much eg a workshop or garden building supply. Link to comment Share on other sites More sharing options...
Nick1c Posted October 10, 2018 Author Share Posted October 10, 2018 Here are some more pics which may help shed some light on things. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 10, 2018 Share Posted October 10, 2018 Definitely looks like two supplies coming in, assuming that incomer on the extreme right goes into the top of the cut out at the top right. Lots going on there, too, and it does looks as if the installation may have had a separate supply run in to feed storage heaters. Link to comment Share on other sites More sharing options...
ProDave Posted October 10, 2018 Share Posted October 10, 2018 Very strange supply arangement there. Can we have a picture more square on to the two supply heads and showing what happens above the top one please. It does look like the top supply just feeds the off peak. Were there an unusually large number of storage heaters perhaps? Get one removed and just 1 supply left for the new build. And in the mean time, be careful of that contactor in a metal box to the left missing it's lid and exposing live terminals. Link to comment Share on other sites More sharing options...
Nick1c Posted October 10, 2018 Author Share Posted October 10, 2018 There was a lot of night storage heaters (now removed). Does it suggest a low power supply? I will be running the new place on electricity only, prob with an ASHP . Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 10, 2018 Share Posted October 10, 2018 59 minutes ago, Nick1c said: There was a lot of night storage heaters (now removed). Does it suggest a low power supply? I will be running the new place on electricity only, prob with an ASHP . A lot of night storage heaters would explain it. A normal domestic supply is rated at around 15 kVA, so if the place had a lot of storage heaters then it wouldn't be hard to use all the capacity of a single supply for this, which probably explains why the second supply was put in to run them. As both cables are on the same pole connection from the look of it, then I doubt there's a network limitation locally. A new build isn't likely to need more than a single 15 kVA supply, unless it's a pretty big house. Generally it's easier to just get a 3 phase supply if the demand is high, but that wouldn't work easily for a house full of storage heaters. Link to comment Share on other sites More sharing options...
ProDave Posted October 10, 2018 Share Posted October 10, 2018 It's an interesting fudge for a supply capacity issue, as the neutral for both supplies is strapped together (it has to be for the dual rate meter) I am sure it would not be installed like that now. I have heard of, but never seen a summation supply to give greater capacity, but never one supply for normal loads, and one for off peak loads. As there is only 1 meter, there will only be 1 MPAN and 1 standing charge I would expect. Lets hope it does not cause too much confusion when getting the supply altered for the new build. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 10, 2018 Share Posted October 10, 2018 Complete guess, but I suspect it comes down to the DNO cable rating, and not being able to apply diversity to the storage heater load. We know that DNOs routinely use much smaller cables than would be allowed on the consumer side, so perhaps they chose to run two cables from the same connection on the pole to the house just to get more continuous capacity without an excessive cable voltage drop. Still can't understand why they didn't just fit a single larger cable, though. We've ended up with a pretty massive 35mm2 incomer for some odd reason. No idea why. Link to comment Share on other sites More sharing options...
Nick1c Posted October 10, 2018 Author Share Posted October 10, 2018 Sorry, I have no idea what MPAN & DNO means. Link to comment Share on other sites More sharing options...
PeterW Posted October 10, 2018 Share Posted October 10, 2018 MPAN - Meter Point Administration Number, or basically the network identifier for your meter at your address DNO - Distribution Network Operator, or the company that provides the wires to your address Clear as mud..? Link to comment Share on other sites More sharing options...
Nick1c Posted October 11, 2018 Author Share Posted October 11, 2018 Thanks Peter. No more pics today as we are enjoying biblical conditions & I might drown if I go outside now, 65mph winds tomorrow...... It sounds as if the best course of action is to ensure that the potential maximum power delivery is adequate from a single supply and if this is the case to loose the second one. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted October 11, 2018 Share Posted October 11, 2018 23 minutes ago, Nick1c said: Thanks Peter. No more pics today as we are enjoying biblical conditions & I might drown if I go outside now, 65mph winds tomorrow...... It sounds as if the best course of action is to ensure that the potential maximum power delivery is adequate from a single supply and if this is the case to loose the second one. Looks like you have two 100 A fused supplies, based on the lower cut out fuse marking, so they are both pretty standard 15 kVA* domestic supplies I think. One 15 kVA supply should be enough for a new build, unless it's going to be very large or have some unusually high loads. * 100 A and 15 kVA don't tally (15 kVA at a nominal 230 VAC is 65 A), as the DNO fuse is there to protect their cable, and the DNO nominal 15 kVA rating can be exceeded for short periods of time, plus there is an allowance for the power factor being less than unity, I believe. Link to comment Share on other sites More sharing options...
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