1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

3ph to Single Phase

Discussion in 'Electrics UK' started by funinacup, 20 Aug 2021.

  1. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    37,156
    Thanks Received:
    1,290
    Country:
    United Kingdom
    Didn't that go out with the 14th/ 15th Ed.?
     
    • Like Like x 1
  2. Sponsored Links
  3. Notch7

    Notch7

    Joined:
    15 Sep 2017
    Messages:
    25,412
    Thanks Received:
    1,792
    Location:
    S. Uplands
    Country:
    United Kingdom
    yup thats what it boils down to it

    you could probably do it quicker than the time taken to read this thread :D
     
  4. crystal ball

    crystal ball

    Joined:
    28 Apr 2004
    Messages:
    5,382
    Thanks Received:
    324
    Country:
    United Kingdom
    I think it did, I remember going to great lengths to keep SP stuff on the same phase, then we got the ok from upstairs not to do it
     
    • Like Like x 1
  5. 333rocky333

    333rocky333

    Joined:
    12 Jan 2008
    Messages:
    8,429
    Thanks Received:
    902
    Location:
    Essex
    Country:
    United Kingdom
    Is that necessary, would it be any more hazardous than a machine with Three phase in it or a 3 phase lead to a machine, go in any commercial kitchen and their single stuff s is balanced over 3 phases
     
    • Like Like x 2
  6. 333rocky333

    333rocky333

    Joined:
    12 Jan 2008
    Messages:
    8,429
    Thanks Received:
    902
    Location:
    Essex
    Country:
    United Kingdom
    Am I missing something , why use leads or adaptors.
    Surely just fit the 5 pin plug on to the single phase lead of the machine
     
    • Like Like x 3
    • Thanks Thanks x 1
  7. funinacup

    funinacup

    Joined:
    30 Aug 2019
    Messages:
    46
    Thanks Received:
    0
    Country:
    United Kingdom
    This is the best post in this thread, by a country mile! Why I didn't think of that I do not know, haha!
     
  8. Harry Bloomfield

    Harry Bloomfield

    Joined:
    30 Dec 2018
    Messages:
    8,483
    Thanks Received:
    1,163
    Country:
    United Kingdom
    Apparently not any longer, the Regulations changed. The difference between a 3Ph item and two 1Ph items is this.....

    If the earth on a 3Ph item became faulty and a phase make contact with the metalwork, the metalwork will then be live and at a potential of 240v to earth. If two or three phase make contact, then the MCB will trip. Should two separate 1Ph items suffer that same fault and be adjacent to each other, then should you make contact with the metalwork of both items you would be across the much higher potential of 415v.

    The likelihood is quite remote, but it can happen and the first possibility happened to me, some years ago. I walked into a flooded and dripping banking hall in the dark, already wet through from rain. A metal cased drier had a faulty earth and the casing was live. They had originally been installed with RCD's, with the one for this particular machine had been removed by an incompetent idiot, because they assumed that because it was tripping, the RCD was faulty. As a result, I was thrown by the 240v shock the length of the banking hall. I was lucky I was thrown, rather than being grabbed.

    Now imagine a similar scenario but your making contact with the live bodies of two machines, on two different phases, 415v.
     
  9. plugwash

    plugwash

    Joined:
    28 Mar 2004
    Messages:
    9,596
    Thanks Received:
    378
    Country:
    United Kingdom
    You are essentially describing a quadruple-fault condition at that point, two separate* earth failures, plus two separate failures of basic insulation.

    * If the two appliances cases were connected to the same failed earth feed then it would be the same as the three phase machine scenario.
     
    • Like Like x 2
  10. Sponsored Links
  11. Harry Bloomfield

    Harry Bloomfield

    Joined:
    30 Dec 2018
    Messages:
    8,483
    Thanks Received:
    1,163
    Country:
    United Kingdom
    That was a circumstance the Regulation makers originally had in mind, when they brought out that regulation. They obviously thought there was a sufficient risk back then. i must admit, I thought that regulation was still in force.
     
  12. SUNRAY

    SUNRAY

    Joined:
    28 Jul 2009
    Messages:
    5,617
    Thanks Received:
    430
    Location:
    Kent
    Country:
    United Kingdom
    I thought I'd put that in my first post... oh well must try better
     
  13. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    48,667
    Thanks Received:
    3,191
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    I don't know about the regulatory situation (although I have seen lots of things written by people about it) but, as plugwash has said, any concerns appear to relate to such improbably situations of multiple simultaneous faults that they probably do not need to be considered by regs. More generally, if it was considered necessary to plan for such 'multiple fault' situations, that could lead to some pretty ridiculous regulations!

    On the contrary, if there are multiple single-phase sockets derived from a 3-phase supply, I would be personally be tempted to suggest that the advantages of balancing the load across the phases would probably outweigh the 'perceived disadvantages' of having nearby sockets on different phases.

    Similarly, I have always been a little worried by the "Danger - 415 [or 400] Volts" labels - which are/were 'required'. At least in relation to the unwary/uninformed, that almost implies that they do not need to take as much care if "only" 230 volts exists within an enclosure!

    Kind Regards, John
     
    • Like Like x 1
  14. AndyPRK

    AndyPRK

    Joined:
    4 Jan 2009
    Messages:
    5,892
    Thanks Received:
    593
    Location:
    Herefordshire
    Country:
    United Kingdom
  15. SimonH2

    SimonH2

    Joined:
    4 Nov 2010
    Messages:
    5,847
    Thanks Received:
    596
    Location:
    Cumbria
    Country:
    United Kingdom
    It should be exactly the right plug for the 16A outlet.
     
  16. AdrianUK

    AdrianUK

    Joined:
    22 Sep 2009
    Messages:
    615
    Thanks Received:
    91
    Location:
    Nottinghamshire
    Country:
    United Kingdom
    True enough ....... unfortunately the OP has 32A sockets....:p

    That supplier has some rather..... interesting leads in his collection. One is a 32A 3P+N+E plug to 16A 3P+N+E in-line socket plus 16A 2P+E socket, without any inline protection. And the infamous 32A to 2 x 16A unfused splitter.

    Now I know that some of us do have similar things in our "get-you-out-of-a-mess-under-carefully-supervised-conditions" box but I'm not sure I'd ever commercial sell one of these!
     
    • Like Like x 3
Loading...

Share This Page