2391-10 Practical assessment

[clematis432]

Thanks for the advice on my recent thread. One more thing I don,t know.

When calculating or measuring ZE on the single-phase board, do you R1+R2 the sub-main cable and add this to ZE at origin to get single-phase board ZE

Or do you do a ZS test at single-phase board incomer and this becomes the ZE of single phase board. Hope I,ve explained this properly. Thanks again.

 

[Brian 157]

According to the C&G marking schedule Zs may be measured or calculated, I can't speak for other assessors but I prefer to see it measured at the sub-board. Most candidates do Zs tests at all points but many calulate the three phase starter/motor circuit. Some loop testers trip the RCD so again calculating Zs for RCD protected circuits is acceptable.