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Discuss inspection & test, disconection times & maximum zs allowed in the Periodic Inspection Reporting & Certification area at ElectrciansForums.co.uk.

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  1. vincef
    Online

    vincef Guest

    Hi,

    on a tn system, 238vs, would the disconnection time be 0.4s or 0.2s, i thought as over 230vs it should be 0.2s, but working with another engineer who disdagreed & pointed out tables in bs7671 show 0.4s to 5s?
    Also when completing certs should you include the 80% or not in the maximum allowed zs box?
     
  2. Jay Sparks
    Offline

    Jay Sparks Forum Mentor

    Location:
    Bratford
    Hi,

    You use the max Zs from the regs book for the cert and you only apply the 0.8 to these readings when your comparing your measured Zs results. However you dont need to use the 0.8 rule of thumb when comparing your measured results with the ones in the osg, as these have already been done for you.

    Jay
     
  3. tony mc
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    tony mc Electrician's Arms

    You also use the 0.4 sec for TN systems as Uo is 230 volts .
     
  4. telectrix
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    telectrix Scouser and Proud of It Forum Mentor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    disconnection time for circuits<32A is 0.4 secs . on a TN system. your 238V is classed as 230V nominal although it's really 240V.
     
  5. SPARTYKUS
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    SPARTYKUS Electrician's Arms

    Location:
    Shropshire
    No it isnt, we harmonised with europe, especially Greece, so it must be exactly 230 all the time.
     
  6. telectrix
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    telectrix Scouser and Proud of It Forum Mentor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    don't get me going on yewrup. i''lll end up getting a ban, bloody foreign bureaucrats telling us what to do, we need another agincourt, trafalgar, waterloo, el alamein, grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
     
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  7. telectrix
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    telectrix Scouser and Proud of It Forum Mentor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    the foundations of Westminster Abbey are shaking. it's Winston turning in his grave.
     
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