Normally I do full complete rewires of houses, but a job has come up that needs an extension.At the main supply of the existing house there is 2 fuseboards one doing the existing house and one with the tails going into it not supplying anything.The work is basically another house being built onto the existing.These 2 boards are on the same phase tails so you have got 2 boards on the same tails.My idea was to just change the board not doing owt to an up to date board and wire new extension from this point.The old existing board is an old board supplying the existing house.Obviously Im going to have to add up the loads to see if it comes close to the incomer 100 amp or whatever.Ideally is that what Im aiming for at the supply one board existing one for extension or have you got any more ideas?Worst case scenario a dont want to be pulling all cables in and then theres too much load on it.This would be put down as an extension too an existing circuit a suppose.Whats your ideas?
extension
- Thread starter r.b
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I would replace the old board with a switchfuse and run a swa to a new consumer unit in the new property. Are both properties going to have gas heating
Are they the same "household"?
Is there going to be any "new" people living there?
What is the incoming supply?
I would possibly use 2 boards depending on the distance from the origin to the load centre of the new part of the building.
The 2 boards could be located together or one in the new area, again this depends on the distance to the load centre, the loads, the layout and the "domestic situation"
As Slips says, a switch fuse & SWA sub main is an option.
Is there going to be any "new" people living there?
What is the incoming supply?
I would possibly use 2 boards depending on the distance from the origin to the load centre of the new part of the building.
The 2 boards could be located together or one in the new area, again this depends on the distance to the load centre, the loads, the layout and the "domestic situation"
As Slips says, a switch fuse & SWA sub main is an option.
No more load then, thus, no upgrade of incoming supply needed?...
I thought id just keep the existing board going for the existing house going.Then just put in a new board for the extension been built on to the house?A didnt check the supply probly a 100 1361 fuse.It would be like running 2 houses off the same load (line).Am not confident about doing it as I say fare enough a total rewire!
If the DNO fuse is holding now, as long as you are not putting electric heating of any sort in I would not worry.
It's fine to use 2 boards.
I have 3 in my own house.
1 @ origin for house & some outside lights, and feed to garage, garage board feeds garage, sockets, lights and some outside lights, & shed 1, along with sub to shed 2 with a board in there for lights & sockets.
Total breakers add up to around 250A probably, we run an 80A main fuse. (I was there when DNO Tech fitted it!)
Shower 45, cooker 45, house ring 32, lights 2x6, immersion 16 on the house board.
As long as your total load x 0.3 is around 60-100A you'll be fine with the existing DNO supply.
As far as the boards & sub mains go, then it is fine to have 2 boards at the origin, or 1 there and a sub main to the other.
It's fine to use 2 boards.
I have 3 in my own house.
1 @ origin for house & some outside lights, and feed to garage, garage board feeds garage, sockets, lights and some outside lights, & shed 1, along with sub to shed 2 with a board in there for lights & sockets.
Total breakers add up to around 250A probably, we run an 80A main fuse. (I was there when DNO Tech fitted it!)
Shower 45, cooker 45, house ring 32, lights 2x6, immersion 16 on the house board.
As long as your total load x 0.3 is around 60-100A you'll be fine with the existing DNO supply.
As far as the boards & sub mains go, then it is fine to have 2 boards at the origin, or 1 there and a sub main to the other.
Don't fall into the max demand trap..
Remember that 4 people in a small house (with say 3 circuits) will tend to use about the same amount of electricity as 4 people living in a mansion (with say 30 circuits)
OR
You have a house with 3 circuits - 30A cooker, 30A sockets & 5A lights... Max demand of say 50A
You rewire it with a 32A cooker, 32A kitchen sockets, 32A D/S sockets, 32A U/S sockets, 6A D/S lights, 6A U/S lights, 6A smoke alarms.... Now by the book the max demand will have gone up (can't be bothered working it out, but it'll be much nearer to 100A), but they've got the same stuff as before,,,, it's just split across more circuits.
Remember that 4 people in a small house (with say 3 circuits) will tend to use about the same amount of electricity as 4 people living in a mansion (with say 30 circuits)
OR
You have a house with 3 circuits - 30A cooker, 30A sockets & 5A lights... Max demand of say 50A
You rewire it with a 32A cooker, 32A kitchen sockets, 32A D/S sockets, 32A U/S sockets, 6A D/S lights, 6A U/S lights, 6A smoke alarms.... Now by the book the max demand will have gone up (can't be bothered working it out, but it'll be much nearer to 100A), but they've got the same stuff as before,,,, it's just split across more circuits.
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I would question the long term motives.
Me thinks first build extension, doubling the size of house.
Then later on, apply for permission to divide it into two dwellings. Easier to get PP than asking at the start to build a new house.
So just in case that's their long term plan, I would stick with S&S's suggestion of a submain to a new CU somewhere in the extension. Then it will be a whole lot easier to split it onto it's own supply if ever they do divide it into two houses.
That sounds like a good plan
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