N
Nigel
Just what I can reasonably do practically, tightened all connections, contact cleaner, supplementary bonding.
But there is nothing that can be done to get a Zs lower then the Ze so it was always a design issue.
Discuss High Zs on submains and high Ze in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
Just what I can reasonably do practically, tightened all connections, contact cleaner, supplementary bonding.
Hi - with B63 the max goes up from 0.35 to 0.69 and job's done (?).
That was my thought, if it's tncs then if the pscc is higher than the pefc at the cutout then there is an issue for the dno to resolve, as you'd be measuring the same cable through two different terminals.Have you measured Zn to ensure that your OCPD will disconnect in short circuit conditions?
I have never had to zero out to do a loop test.I’m not being patronising here but with such low value measurements you did remember to zero your MFT first...it is easily forgotten to do so.
If it is 100mA/300mA delay RCD feeding the sub-main and the house CU is all on RCD (or neutral-switching RCBOs like compact Wylex/Fusebox) then you keep final circuit selectivity and avoid marginal Zs limits.Single RCD protecting submain and therefore whole house is not ideal.
The DNO fuse is for overload protection of their network, it is not required to meet the BS7671 regulations on ADS for an installation.And finally.... How is it that my submain reading .29 would not comply but the 100 amp fuse at the origin is quite alright for anything up to 0.8 then?
Reply to High Zs on submains and high Ze in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
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