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Confusion over table 7.1(i) OSG

hertzal123

When I look at line 10 (B40 mcb on a 6/2.5 twin and earth,TNS system the max circuit length due to zs is given as 23m(no RCD).Yet when I calc R1 +R2 x 23m I get 10.49x23/1000 = 0.24 ohms.Add ze for TNS to this(0.8) gives 1.04 ohms,whilst table B6 gives a max zs of 0.88 ohms for a B40.Wondered where I,m going wrong.

                                                                     Regards,

                                                                                      Hz

                                                                     

 

 

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    So I can see why the answer is 23m and maybe the missing 0.01 will turn up in the morning ?

     

    Am off to work shortly, but would the missing .01 be accounted for by the  figure for Zs in OSG B6 being tabulated at 10degC not 20degC? See note OSG page 126. Correction factor in table B8

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  • 0

     

    So I can see why the answer is 23m and maybe the missing 0.01 will turn up in the morning ?

     

    Am off to work shortly, but would the missing .01 be accounted for by the  figure for Zs in OSG B6 being tabulated at 10degC not 20degC? See note OSG page 126. Correction factor in table B8

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