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Spot the mistake...

Discussion in 'Electrics UK' started by eveares, 8 Mar 2019.

  1. eveares

    eveares

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    Regards: Elliott.
     
  2. flameport

    flameport

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    Two phases swapped, so motors will be running backwards.
     
  3. eveares

    eveares

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    Yep, L1 and L3 swapped over.
     
  4. ban-all-sheds

    ban-all-sheds

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    I'm amazed either of you made it that far.

    After less than 20s I decided that anybody who thought that the music they put on that video was appropriate, helpful or useful was, ipso facto, an idiot of the first water who could not possibly be trusted to know anything about anything.
     
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  5. sparkwright

    sparkwright

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    It was right according to the diagram - but the markings on the actual plug didn't match the diagram - right?

    Sometimes you wire these things up in the right colour sequence, and the motor goes backwards, so you still might have to swap two phases over, but we all that basic stuff.

    There's nearly always some kind of mistake in these videos.
     
  6. ericmark

    ericmark

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    I have a phase rotation meter, so when sent to fit a three phase socket I tested it to ensure correct rotation, however what I didn't do was check other sockets in the building, they were all wired wrong direction.

    And when I careful wired a socket for truck freezers to plug into I found the units were inverter controlled so it did not matter which way around it was wired.

    I know at building of Sizewell "B" it was a real problem, as extension leads were plugged into extension leads and if concrete pump went wrong way, it would often be corrected in the wrong lead, so we used a phase rotation meter on every socket and every lead to ensure correct one was changed, but I think that is the only job where I have really used a phase rotation meter.
     
  7. flameport

    flameport

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    The diagram is wrong.
     
  8. 333rocky333

    333rocky333

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  9. flameport

    flameport

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    The socket they are wiring has the correct markings in the plastic - L1 shown where they have L3 on their diagram.

    plugfail.jpg
     
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  10. mattylad

    mattylad

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    Have you told them of their error yet?
     
  11. 333rocky333

    333rocky333

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    Reg 643.9
    It shall be verified that the phase sequence is maintained at all relevant points throughout the installation
     
  12. ericmark

    ericmark

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    Was that in the 16th edition which would have been valid at the time? Original 20th century version.
     
  13. mattylad

    mattylad

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    Is that a gobful way of simply saying, wire them up the same to the sockets/isolators, any swapping phases round must be done in the plug ?
     
  14. SimonH2

    SimonH2

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    I recall "some years ago" at a previous job, we were having some large (to us) chillers installed. So usual stuff, local sparkies arrange a supply and connect it into the unit, then manufacturer's engineer comes to commission it.
    Apparently the whole site is phase reversed, so needless to say, when the engineer hit the switch - the first thing he says is "sounds like the compressor is running backwards". So one by one he's giving the contactors a stab and swapping phases round (3 compressors and 3 fans) - except not everything was running backwards because they'd cocked up the wiring in the unit ! Did make me wonder about the quality control not to spot a fan or compressor* running backwards during testing !
    * These were of a type that makes a characteristic noise when run the wrong way.

    Actually, thinking back a bit, I think the first thing he did was to stab the contactors one at a time to see if the motors were running the right way. I don't think this was the first time he'd found units with internal phase reversals :whistle:
     
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