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  1. James McDonough
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    James McDonough New EF Member

    Location:
    Taunton
    I'm after some advice please guys..

    I've got a job where the builder is converting a shop and flat above into 3 separate flats. There is currently just a 100a single phase supply into the shop on the ground floor.

    I have requested a new three phase supply to be installed, which will be located on the ground floor and will eventually be the hallway for the 3 new flats.

    So in the hallway will be a three phase supply and three meters (one for each flat). I then need to run a cable from the meter to the consumer unit in each flat and trying to work out the best way to do this.

    Has anyone done this before as has any good suggestions?
    The supply cable for each flat will ideally have to be inside the wall and floor at some point so if I use t&e it will require a 30mA RCD. Which will then cause issues because it may trip before the consumer unit RCD. Also thought about using a time delayed RCD but I can't seem to find a 30mA version out there.

    Thanks in advance!

    James
     
  2. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Whilst there are a few time delayed 30mA RCDs out there, it would not be acceptable to use one in the situation you describe.
     
  3. SparkyChick
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    SparkyChick Making a banana smoothy for my fave gorilla Electrician's Arms

    Location:
    South Wales
    Business Name:
    SparkyChick
    Switch fuse for each flat feeding a 16mm or 25mm (depending on suppliers fuse) 3 core SWA. Put the earth in the cable, earth the armour at the origin of the supply.

    Terminate in a 2 gang back box behind the CU and bring the supply in from the back, or just terminate directly to the CU.

    That's how I'd do it :)
     
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  4. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    No such thing as an s type, 30ma rcd is there? As SC says swa cable suitably glanced at both ends.
     
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  5. Electric Magic
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    Electric Magic Electrician's Arms

    Location:
    Manchester
    Good advice. Although you can size the cable based on the size of the fuse in the switch fuse rather then the supplier's fuse.
     
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  6. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    I believe some Chinese companies produce them.
     
  7. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    Something like this??? Those Hager are cam lever HBC fuses. IMG_3385.JPG IMG_3386.JPG
     
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  8. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    P.S. not my work.
     
  9. KEV 1 N
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    KEV 1 N Regular EF Member

    Location:
    Durham
    We did some flats several years ago, where the main supply and meters were located in the basement. We ran a split concentric cable to each flat
    image.gif
     
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  10. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    That requires additional rcd protection if in a wall without earth containment.
     
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  11. Andy78
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    Andy78 Trusted Advisor

    Location:
    Kingston upon Hull
    SWA would be my option too. Saves having to use extra protection against impact or other measures to avoid having to RCD protect the distribution circuit.
     
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  12. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Switch fuse and swa is the only option
     
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  13. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    The easiest option but not the only solution.
     
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  14. KEV 1 N
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    KEV 1 N Regular EF Member

    Location:
    Durham
    The flats were done in 2006, so rcd protection wasn't required.....SWA is the best way to go, may be cheaper to run a seperate earth cable along side 2core swa as opposed to buying 3 core.
     
  15. dinger809
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    dinger809 EF Member

    Location:
    Essex
    Business Name:
    .
    Did this a couple of months ago. Three phase supply into Ryfield Board and then each individual supply out, through meter, isolator switch and to each flat using 3 core armoured.
     
  16. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Of course, if the Gas and Water are supplied in plastic, there would be no need for a separate Earth conductor.
     
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  17. Leesparkykent
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    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    This will come under what's called a Building network operator installation. The DNO will give you guidance on what they want but a single point of isolation for the building will be needed and a ryefield board or similar so it can be sealed. Normal layout is head, fused switch or isolator depending on the distance, ryefield, Meter, switch fuse or isolator them armoured cable to the flat. You have to get it all in place leaving the connection ready for the DNO to connect in to the head and have the tails in place from the ryefield to the meter and from the meter to the switch fuse/isolator ready for the meter operator to connect.
     
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  18. Leesparkykent
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    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    you can't run plastic gas pipes in a building as it would be catastrophic in a fire. If the gas is run in plastic externaly it has to change to be being metallic before it enters the building. The yellow plastic pipe feeding external gas meters is not allowed to be exposed so again needs to change to be being metallic before it comes out of the ground.....in other words it's pretty hard to get away with not bonding gas.
     
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    Last edited: Nov 11, 2017 at 5:50 PM
  19. dinger809
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    dinger809 EF Member

    Location:
    Essex
    Business Name:
    .
    I wish I’d taken a bit more time in my reply, but that is exactly what I did! Thank you for the perfect explanation
     
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  20. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Would you need a switch fuse after the BEMCO or ryefield as you call it? or just from the BEMCO via meter and double pole isolator as you would have potential say 2 60 amp fuses in series and it’s a different set up to say a house where the tails are greater than 3 meters and is the origin of the supply?
     
    Last edited: Nov 11, 2017 at 5:59 PM
  21. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Hmm, seen quite a few yellow plastic pipes connected to internal meters. Have even seen them bonded.
    Yes the internal pipework has to be metal for gas, that is if there is gas.
    The internal pipework for Water can be either metal, plastic or a mixture of both.
     
  22. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Do you mean were they connect to the meter externally?
    Because where the gas enters the building is always in copper as it has to be , at least that’s what I’ve always experienced
    I suppose the question is that the pipework entering the property, is it extraneous?
     
  23. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Doesn’t have to be copper where it enters a building.
     
  24. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Like I say I’m not a gas engineer but I’ve never seen plastic gas pipes enter a building from the outside
     
  25. Leesparkykent
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    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    Tell you the truth Ian we just install switch fuses but reading the info the DNO supply you with, you could use a DP switch as you have the fuse in the Ryefield/BEMCO board. 9/10 times the flats we do a 60A supply is adequate so 100A fuses in Ryefield and 60A fuses in the switch fuses. Using the rule of thumb of x 1.6 for discrimination between upstream and downstream fuses of the same type then discrimination is just about achieved. I prefer it this way if it's possible so if there was a fault, the fuse in the switch fuse goes and an electrician can replace it rather than entering a sealed Ryefield which is frowned upon by whoever sealed it.
     
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  26. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    I have seen yellow plastic gas pipes in cellars, have seen them enter buildings above head height (though outside on the external wall, the plastic pipe was inside metal tube.
     
  27. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    That’s a good way of looking at it lee.
    Just we’ve done a few buildings/flats with BEMCOs and then double pole switches to flats as we consulted the DNO and they saw no problem with it and the BEMCO boards were fed from fused isolators anyway and via a single source of isolation.
    We only had 63 amp fuses in the BEMCOs as the supply to the 1 bedroom flats were only 16mm swa so we saw no point in having 2x 63 amp fuses in series.
     
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  28. Leesparkykent
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    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    Plastic pipe for gas is not allowed to be used within a building at all...The options are copper, barrel or tracpipe. Externally plastic pipe is allowed to be used but not exposed so it has to change to one of the pipes mentioned above or be covered so it's not exposed.
     
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