Table 41.3 of BS 7671 stipulates the maximum Zs for circuits.
Having printed off the impedance results for a project a number of circuits are in excess of the maximum permitted zs from table 41.3
How does Connect carry out a calculation, and then flag up the non compliance / failures with BS 7671 table 41.3?
I have only been made aware of the faults when the site test results have indicated that tested earth fault loop impedances are in excess of table 41.3. Then having looked again at the calculations in Connect with the board calculation sheet and having to manually check against table 41.3.
Is there a function within Connect for indicating circuits in excess of the value in table 41.3 like there is for the volt drop?
If not surely as a calculation package for compliance with BS 7671 it should be included
Stuart0 - the software should flag any earth fault disconnection issues in the "end of calculation" report. You should bare in mind, however, that rather than use a table of figures, the software considers the equation in 411.4.5 (this is allowed for by the statement in 411.4.7)
If there a specific item in a project that you wish us to examine, then please let us know.
Duncan Brown
Duncan,
Thanks for the response.
In summary, as long as the permitted disconnection is achieved a higher Zs than table 41.3 is permissible.
Stuart0 - We usually find that where we can incorporate formula's rather than lookups, then the forumula will give a more accurate representation. This could differ from the table slightly.