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SPD arrangement

lyledunn
24e119d041831991ba57ac52261a5c57-huge-e2f7a6a0-5147-4eb4-b505-80e94f626124.jpg
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    lyledunn:

    Exactly Graham. However, both CT1 and CT2 are presented as an “example” of such connection arrangements. That implies that there is more than one way to comply. 

     


    Yes, that's true. It does depend what you're trying to achieve, and also sometimes whether the installation has an LPS - although if that's the case, BS 7671 bails on you and refers to BS EN 62305 series !


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    Am I right in thinking this a training centre and there's a SPD in every booth in the workshop or is there just one at the main intake?


    Is this possibly one of the most protected installations in the UK?




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    Andy,

    Training only represents about 20% of what I do. This was a a remote DB in a pharmaceutical company. The SPD was apparently part of the requirements for the installation of a new picking machine. I haven’t seen instructions for either SPD or machine but I do recall the same SPD on another job and vaguely remember instructions referring to TNC. I will try to get said details over the weekend.
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    The time it takes the pulse to go 15 metres, realise there is a short at the far end and come back again  is 'long' compared to the rising edge of the transient.

    In the time that is happening a large voltage can exist between N and E.

    Do not wait, fit the blue link.

    mike.
  • 0
    fit the blue link.

    and possibly a longer busbar too...

       -  Andy.
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    Having determined it’s a not a theoretical answer, I’m with Mike, get the blue link in ASAP as an #### covering exercise.


    Installing the blue link cannot cause any problems can it?
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    Looks like Andy's right - will probably need a 4-finger busbar too
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    That’s no hassle, there’s spare busbars in the back of the van.
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    Which begs the question, did the guys who installed the SPD have spare busbar on the van?


    I assume that enclosure was sold as a two way consumer unit, so the busbar is long enough to connect two protective devices to a main switch.


    So when they came to install the SPD was the decision not to connect the neutral ultimately based on avoiding a trip to an electrical wholesalers with the thought being it doesn’t really need the neutral connection.


    Or did they get a  hacksaw and cut off the fourth pin having made a design decision that the neutral connection is not required.


    My money would be on it being “It doesn’t really need it and it will save a trip to a wholesaler”.
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    Reading what Lyle says, perhaps it is a 3 phase machine with no neutral connection. To me, that seems fairly likely. It is not a requirement to have a neutral anywhere in a 3 phase installation. No worry there then.

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