Combining two supplies

I have recently bought an old house well actually its two houses which is part of the problem. The house was originally 2 buildings and until recently one was uses as a shop so had a commercial electric supply while the house has a separate domestic supply. (Incidentally the shop supply is actually 3-phase - previously a saddlery - although 2 phases are header only). The wiring in general is awful, the house supply doesn't even have a distribution board just a collection of circuit switches. I would like to get rid of one supply (I don't like paying 2x standing charge) but don't want to re-wire before doing so. The distribution 'areas' are actually quite close together (~1m separation). My prefered option is to put in a 100A switch/fuse so that I can work on the circuits safely later, followed by a connector block to split the tails to the two sites. Is this OK on a TT installation? and will I have a problem getting the board to re-connect to it given that the earth is not really satisfactory - currently only 4 or 6mm2 earth wire from the electrode to the distribution 'area'? If it is OK where can I get a switch that has terminals large ebough to accept the meter tails. Some of the answers are in previous threads but I'm not sure if the TT installation creates an issue as I'm used to T-N-C-S on my last house.

Reply to
Stephen Fasham
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I thought the standing charge disappeared ages ago? If you are still paying it, it sounds like you are on a business tariff.. One of our meters read

30p of usage last quarter and that's all we paid.

Tony

Reply to
Tony

Stephen Fasham formulated on Monday :

I would suggest that the only sensible thing to do, in view of what sounds to be a very old installation (lots of separate switch fuses), is to wait until you have the money to rewire the whole lot.

Either continue to pay for both supplies, or have the 3ph supply cut off and make do for a while. Diverting old cables of unknown history and unknown installation safety is fraught with difficulties. I am always wary of the safety implications of making major alterations to such old installations.

If the old 3ph area is not too large, consider installing some temporary circuits in there if you must.

Reply to
Harry Bloomfield

Rather than a switch fuse, choose your final consumer unit with plenty of spare ways and use that instead, mounted in its final location. Run the old dodgy installations off their own 32A MCBs on the RCD side (or better, off

32A RCBOs). As you rewire, attach each new circuit to the new consumer unit. Eventually, you can disconnect the old installations, reusing the MCBs/RCBOs for ring circuits.

As you have TT earthing, you should choose a consumer unit with a 100mA time delay RCD incomer. You then use MCBs for lighting/refridgeration/central heating etc. and RCBOs for socket circuits. Alternatively, get a split load unit with a 100mA time delay RCD incomer and a 30mA RCD and put socket circuits on the RCD side. You can get MK Sentry units ready populated with a

100mA time delay RCD (and 30mA for split load).

When you discuss your requirements to remove one of your supplies with the supplier, ask if TN earthing is available. It is increasingly so, even in rural areas, although possibly might not be economically viable.

Christian.

Reply to
Christian McArdle

I was in a similar situation when we started joining two cottages together. One had an old but ok supply/fusebox, the other was a total disaster.

I had the worst one disconnected and then installed a new consumer unit which will eventually become the only supply for both houses.

Re-wiring becan on the worst half and new cables were run to the new consumer unit.

Power for the consumer unit comes from a 10mm cable connected to a spare

30A fuse in the old fuse box. Yes I know not ideal and I can't connect up the cooker but at least the lights and one ring main are working.

A new meter is being installed in a more suitable location and when that's complete "The Big Switchover" will happen ie The consumer unit will get power from new tails to the new meter and all wiring from the old fusebox will be moved over to the new consumer unit. Finally the cooker will be moved across.

Nick Brooks

Reply to
Nick Brooks

No, standing charges still exist either for new supply or legacy. But even with accounts with "no standing charge" you normally pay a couple of pence more per unit for the first few hundred units each quarter so if you useage is "normal" you still pay more or less the same amount.

Hum, good call for very low useage. I must investigate that for a our two very low useage meters, time to break out the spread sheet again for break even points...

Reply to
Dave Liquorice

"Stephen Fasham" wrote | I have recently bought an old house well actually its two | houses which is part of the problem. | I would like to get rid of one supply (I don't like | paying 2x standing charge) but don't want to re-wire | before doing so.

Ask the electricity supplier to amalgamate the two meters onto the same billing account.

Owain

Reply to
Owain

Just a thought. Is the whole property registered as two households as far as the council is concerned? If not, it would make sense to keep 2 separate supplies in case you want to apply for a certificate of lawfulness - having

2 supplies is useful evidence, and the value of the property might be considerably more, and you wouldn't need to apply for planning permission to create 2 households. In the future you might want to take advantage of this situation.

Hugh

Reply to
Hugh

If you`re knocking them together you`re only supposed to have one point of supply anyway under the supply regs from what I remember (danger of cross-phasing etc)... to get a disconnection you will probably have to ask the supplier (who you pay the bill / standing charge to) to send a D132 flow to the local REC for a physical disconnection, and another to the meter operator (not sure what that flow is called though)

"flows" are electronic notes that are standard communication forms between suppliers / meter operators / network operators as laid down by the regulator, so the supplier should know what they are :-p

Reply to
Colin Wilson

The house has been one building since about 1880. The electricity company will take away the one supply for free as they have already agreed to replace the supply cabling to the property as its completely knackered (frayed braiding, corroded upstand etc.). The reason I don't want to put the final consumer unit in now is that I'm in the middle of a planning application for change of use from A1 (retail) to C3 (residential) and the cost of full re-wiring is taken into account in my argument over the shops non-viability, but not if I've already done it.

On a technical note, having looked at the replies so far is a good/acceptable solution to put a separate 100A, 100mA time delay RCD (e.g. MK6400S) in a separate enclosure next to the meter I want to use in the longer term and then run tails from this to the consumer unit? Then when the other supply is removed I can switch off the supply and put in a 100A connection box to put the other supply in temporarily.

The reason I don't want to just re-wire everything straight-away is that the house is huge, basement + 3 floors and is set up so that I can re-wire it in sections i.e. split the ground floor in half each with it's own socket ring and lighting circuit, and then each of the bedroom floors on its own. Otherwise since re-wiring is an evening and weekend job I don't have to live in a complete tip for however long it takes (my last house took 3 weeks but that was only 800sq ft whereas this one is 2500sq ft.

Any comments on the separate RCD idea welcome.

Reply to
Stephen Fasham

Seperate RCD is fine. If you want to clear up afterwards when you have the new consumer unit and your planning permission, the RCD itself can then be removed and placed in the consumer unit box instead, for a smaller installation with fewer boxes. If you do this, ensure the consumer unit is an insulated plastic type. Metalclad is not permitted for TT installation with the main RCD in the box. Alternatively, use a large consumer unit as the RCD enclosure, but don't stick anything on the DIN rails until you are in a position to rewire.

Keep the tails short. The RCD has no overload protection, despite the 100A rating. The total tails between the meter and the consumer unit must not exceed 2m without permission from the supplier. If you need longer tails, then definitely use the consumer unit instead of a small enclosure. Then feed the long tails to the existing installation via a 50A MCB. Don't use any electric showers without checking that the cooker and any laundry appliances are off.

Christian.

Reply to
Christian McArdle

Thanks guys, I think I'm there now. The 2m limit is not a problem since the two meters are only about 1m apart, separated by a hall and a wall. I think I'm going to go for the separate RCD enclosure as space is not a major constraint so there is no need to combine it into the eventual consumer unit, and I like the idea of being able to disconnect the supply to the CU without having to call out the supply company. Actually the thing taking up the most space is the collection of headers for the 3 phase conductors but hopefully since the external supply is being 'dealt with' I can get 2 of these removed which will neaten the whole thing up - but we shall see.

Reply to
Stephen Fasham

I'd keep them. You might want them reconnected in the future, especially if you start considering storage heating, or multiple electric showers.

Christian.

Reply to
Christian McArdle

The OP has many options, some safer than others. But one thing I would not want to do myself is to continue running an install so historic that it doesnt even have a CU. Such installs were rough when fitted new, but after a fair portion of a century their condition surely presents an immediate danger of electrocution and fire.

As far as connecting such a thing to an RCD I would not be surprised at all if the RCD just pops immediately. The various connections will be encrusted in dirt, forming leakage paths, the rubber (if its lucky enough to be rubber) will have disintegrated, and the more likely paper or polybutyljute insulation will be in a similar state, and in the case of paper it may be damp. Certainly the paper capacitors I've come across from the 30s have all been damp and very leaky. Also any movement at all of any wiring so old may make it short and cause a fire. I have seen post war rubber in metal conduit wiring where a good half of the rubber had fallen off, and the least movement anywhere would cause a short. Yours is presumably older.

The conductors may be steel and generate heat in use, and maybe have rusted, earthing may be non existent, ditto any sign of double insulation, or even any insulation at all after all these years.

I think any electrician recommending use of such could potentially get themselves in real trouble legally, and any householder using such a setup is taking a risk to their lives. And fwiw I'd be surprised if an insurer would pay out if it caught fire.

OTOH what do you do when you dont want to rewire? I would disconnect the dangerous wiring, as I dont see any other sensible option. Living with no fixed wiring in half the house and lights on extension leads is surely better than that, and only costs a drum of flex and a few sockets. And it only strengthens your case for change of use, especially if you have an electrician put in writing how dangerous it is and strongly recommend immediate disconnection, and then confirm disconnection.

However I dont know what if any regs cover temporary flex wiring, so I wont recommend doing it. You'd need to find out whats kosher yourself.

Regards, NT

Reply to
N. Thornton

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