Use electric shower's circuit to install sockets

Discussion in 'Electricians' Talk' started by ProTofik, Aug 27, 2021.

  1. ProTofik

    ProTofik Member


    I will soon have my house converted from oil to natural gas. As part of this conversion, I am getting rid of electric shower.

    Right now, electric shower's power cable goes directly from customer's unit in the kitchen, through the attic, down to the bathroom. As I will be getting rid of the electric shower, I was thinking of just pulling the cable back up to the attic and installing two or three double sockets up there.

    The 9kW shower I use right now is protected by 40A MCB in the customer unit. I assume I will need to replace it with something smaller, but what would be suitable choice? 32A or 16A?

    Also, as there is just a single very thick cable going from the customer unit to the shower that I will be using, the sockets will effectively be on a radial circuit, rather than ring. Would that be ok?

    If I was only to install 2 sockets in the attic, I would connect the thick cable to the first socket, and then run 2.5mm2 cable to the second socket probably on the opposing wall.

    Am I thinking of it in the right way, or have I got some assumptions horrible wrong?
  2. cleggie

    cleggie Active Member

    The existing shower cable would be wrong size for sockets as it should be 2.5mm and is probably 6 to 10mm.So i would think it needs changing too
  3. ProTofik

    ProTofik Member

    That's what I thought, but the cable is already in the wall which is why I want to keep it. What if I got that cable into junction box first, and from it I would run 2.5mm2 cable? That would effectively 'downsize' it to the right size.
  4. seneca

    seneca Screwfix Select

    A 16a or 20amp breaker would be appropriate, I assume you do have RCD protection on the circuit?
  5. ProTofik

    ProTofik Member

    See attached picture. That's my customer unit. The left hand side fuses/MCB are protected by RCD, right right hand side ones aren't. Shower is protected though.

    By the way, I know what each fuse/MCB on my unit is for except for the 2nd from the right labelled as W.M (WiM?). Anyone knows what it may be?

    Attached Files:

  6. spannerw

    spannerw Screwfix Select

    Washing machine??
  7. Ind spark

    Ind spark Screwfix Select

    You could put the existing 10mm/6mm into a small consumer unit say a 2 way the run a radial off that from a 16 amp mcb ( assuming the old shower was already rcd protected)
  8. ProTofik

    ProTofik Member

    Hah why I haven't thought of that, good shout. I will check if this is it.

    Edit: Yes, it's washing machine. Mystery solved.
    Last edited: Aug 27, 2021
  9. ProTofik

    ProTofik Member

    That's actually a decent idea. If I was to do it that way, would I just leave the 40A MCB in the main customer unit, or should I get different sized one?
  10. Ind spark

    Ind spark Screwfix Select

    If it's 10mm leave the 40 if it's 6mm put in a 32
  11. Coloumb

    Coloumb Screwfix Select

    If you put in a new CU on the end of it you will need to notify the work as adding sox to the cu will be a new ctt. Personally I would use some sort of adaptable box to go from 10/6mm to 2.5mm and run the sox of that. You will for sure need to change to a 16/20a mcb.
    jimbobby and Ind spark like this.
  12. jimbobby

    jimbobby Active Member

    .......or 4mm .
  13. Bazza

    Bazza Screwfix Select

    What will you be using the sockets in the loft for? If a total maximum of 13A is sufficient then forget the suggestions above.
    Simply terminate the 40A circuit to a 13A switched fused connection unit (You'll need a deepish box).Then connect all your sockets to the load side of the FCU.
    No need for a new consumer unit, no need to notify anybody, no need to change the 40A MCB, keep the shower cable. Simples!
    ElecCEng likes this.
  14. Ind spark

    Ind spark Screwfix Select

    Will 10mm even fit into a spur never tried.
  15. Bazza

    Bazza Screwfix Select

    Ind spark likes this.
  16. jimbobby

    jimbobby Active Member

    instead of 2.5mm
  17. ProTofik

    ProTofik Member

    And I think that's even better idea. Should I just run 2 spurs off this box, or do a ring from it? If I remember reading somewhere correctly, no more than 1 spur should be connected to one box.
  18. Ind spark

    Ind spark Screwfix Select

    No just the one spur, as it's fused you can run more than 1 socket.
    Your thinking of unfused spurs.
  19. ProTofik

    ProTofik Member

    Alright, so I think I got it all sorted in my head. Terminate the 6mm2 (I think that's what I have) cable into fused box, then connect 2 sockets, and change MCB to 16A one in the customer unit. No need to notify anyone, easy to do.

    Thanks everyone.
  20. Ind spark

    Ind spark Screwfix Select

    Even easier now you don't have to change the mcb in the consumer unit.

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