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Power Calculation for Cables to be used for a type of industrial Ring Main.

Former Community Member
Former Community Member
Hi there I'm just wondering if I could shed a bit of light on the sizing of cabling required on 4 floor high building who's power requirements are inter-linked with each otpher on each of the 4 floors now these contain Power sources for 110v,230v & 400v.Now there are Welding units who's maximum output when all of them are working is about 64kW.Now my calculations are if the client uses 400v 3phase then I work out the overall current to be just under 100A and recommended a cable of 3 Core x 50mm2 for the total current to run interconnecting the power sources on each of the floors so I'am wondering would this be correct in the size of cable to use. If it is going to be 230v Single Phase then the total current I calculate to be around 240A of which a cable type of 3 core x 120mm2 would be required to interconnect with all 4 Power sources on each of the floors. Could anyone give us an idea as to whether the cable sizes for each of the inter-connected power sources would be desirable?. And also if someone could give us an idea of the cabling requirements for 12 13A domestic sockets running say the full load of soldering irons at each time has to the cabling sizes that would be required on each of the floors and lighting requirements of say 500w for 12 lights.

Regards

Jimmy2Rivers
  • Former Community Member
    0 Former Community Member
    no need to be complicated 

    if your current calculation is correct 

    what you need is think about the current capacity of cable 


    say 25mm2 for 100A section, 95mm2 for 300A section 

    BTW,  for 3-phase LV system usually would use 4/c cables and 2/c for 1-phase 

    ​​​​​​
  • Former Community Member
    0 Former Community Member
    Well yeah I agree about the fact that you need to take into account the current capability of the cable.So I was thinking that with knowing the Maximum Power requirement given by the client for the Welding Machines its easy enough working out the current for the cable but was making sure that this cable size is required throughout the floors from 1st all the way to the top (4th floor).What about the domestic sockets (ie 12 double sockets in all).All on one floor would this be normal twin and earth type cable.

    Regards

    Jimmy2Rivers
  • Former Community Member
    0 Former Community Member
    it is very small demand for 12 lights total 500W. 2.5mm2 should be fine for 13A double socket

    However,  normally we don't put all of the socket into single circuits due to safety reason. it should limited 2-3 double socket in single circuit to prevent improper usage and overloaded. 


    Here is more details for your reference 
    https://www.homebuilding.co.uk/electrics-cabling-circuits-and-switches/

  • Former Community Member
    0 Former Community Member
    In the building the client was arguing over the factor whether to use industrial or domestic sockets. But on the Ground Floor they where looking at using 6 13A Double Sockets in the left corner on the building and another 6 Sockets in the Right side. So was wondering if 2.5mm2 would be enough if say in a worst case scenario all sockets where being used with say operation of soldering irons. Many Thanks Jimmy2Rivers
  • Former Community Member
    0 Former Community Member
    Another question if say on the 230v cable throughout the floors from 1 to 4 is going to be 95mm2 cable would I need to go through a junction box to get to the 12 13A Sockets on the ground floor?.Jimmy2Rivers
  • 0
    What sort of soldering irons are we talking about here?  The small ones for electronics are normally only tens of watts each.  A solder reflow station could be hundreds of watts.
  • Former Community Member
    0 Former Community Member
    Well I think mainly it will be benchwork soldering so I guess just electronics type has there is no room for solder stations.

    Jimmy2Rivers
  • Former Community Member
    0 Former Community Member
    I think for sockets the client has given a 125A protection requirement for the 13A sockets I think was mentioned so going off this the cable size requirement would that be 4mm2 for the 13A sockets but how would this interconnect with the main distribution cable for 230v of say 95mm2 would a junction box be required.

    Jimmy2Rivers
  • 0
    I think you need to do a bit of a cable calculation here, you need to ensure volt drop is within regulation and you also need to ensure you meet the require protection disconnection times too, it not just the current.
  • Former Community Member
    0 Former Community Member
    Yeah, the protection side of things is in a cubicle inside another building we are just cabling up to the structure like a long extension lead from the outer building that contains the protective devices. So we are ensuring that the structure is capable of working so that numerous workers (ie Welders and Cutters) can work safely on the structure for cutting up old oil rigs when they are on land base area. But there is an area for office space within the structure that has these 13A sockets and I was wondering how best to cable up to these from the Main Supply for 230v and the type of cable to use?.

    Regards

    Jimmy2Rivers

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