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Max Zs BS7671 17th Edition / Guidance Note 3 Inspection and Testing

Former Community Member
Former Community Member
Hello,


There seems to be some slight differences with regards to acceptable Zs values when comparing the two documents BS7671 17th Edition A3 and Guidance Note 3 Inspection and Testing 17th Edition A3.


For example table 41.3 from BS7671 17th Edition A3 states:


0.4sec trip D6A = 1.82 Ω


Adjusted to 80% as per appendix 14 = 1.456 Ω



However page 121 from Guidance Note 3 Inspection and Testing 17th Edition A3 states:


0.4sec trip D6A = 1.46 Ω




These two documents are produced by IET. Guidance Note 3 Inspection and Testing 17th Edition A3 is rounding up Zs values above the maximum allowable values detailed in BS7671 17th Edition A3, why is that ?




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Parents
  • Lol ....


    '' The problem in "engineering" terms or any other terms for that matter is 1.4566666667 Ω does not equal 1.46 Ω. ''


    There were a couple of Russians, approx 30 years ago,  living in a New York flat working on the number of decimal places without repitition of Pi. They got to 5,000,000 dps !

    How they managed to get their mainframe up and running in a block of flats defies logic and utility bills !


    Legh...
Reply
  • Lol ....


    '' The problem in "engineering" terms or any other terms for that matter is 1.4566666667 Ω does not equal 1.46 Ω. ''


    There were a couple of Russians, approx 30 years ago,  living in a New York flat working on the number of decimal places without repitition of Pi. They got to 5,000,000 dps !

    How they managed to get their mainframe up and running in a block of flats defies logic and utility bills !


    Legh...
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