High Zs readings | on ElectriciansForums

Discuss High Zs readings in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

R

Rory

Hi, can anyone help?
I've recently carried out a PIR on a school building which has 1 main distribution board supplying 9 other distribution boards around the school. Most of the installation is fine except for a number of circuits which have higher than normal Zs readings according to the given tables.
Each D.B. has BS EN 60898 mcb's and are mostly type c. There are no RCDs throughout the whole installation and most of these circuits are supplying just sockets and lights.
Is there anything I can do to overcome this such as putting type B mcbs in which would make the acceptable readings higher or fitting RCDs to these circuits?
Many thanks.
 
Rory, have you established why they are too high?

Is the R1+R2 from each sub board ok?

is the Ze on the main board ok?

or is it the R1+R2 of the sub-mains that is causing the problem?
 

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