Zs Measurement on plug and play lighting

Modster · Nov 16, 2016

Hi Everyone,
Any advice on the following -
Lighting circuit in a commercial installation (shop), Fixed wiring to Junction Box, The new light fittings are wired using 2.5mm plug and play flex's which are fed from the fixed wired jb's. Where shoul Zs be measured ?
At the end of the fixed wiring ie the jb's.
At the extremity of the circuit , ie the end of line of the plug and play flex's.

My thinking is you still need to meet the 0.4s disconnection at the circuits extremity regardless of how its wired, Others are saying the equipment doesnt form part of the fixed wiring as it is plug and play and the equipment is portable. i disagree with this as the equipment itself is fixed and not meant to be portable in its nature.
Please let me know your thought on this issue.

Many thanks in advance.

westward10 · Nov 16, 2016

I always go for furthest point in the circuit which would be a light fitting. This is the worst case scenario for the protective device with regards to fault protection. Those who say it doesn't form part of the fixed wiring are overlooking the fact there is no intermediate protection between the light and the dist board.

Toneyz · Nov 19, 2016

As Westard10 has posted at the furthest part of the circuit it will also prove LCM.Sometimes it can be probmatic when doing dead tests due to pir relays.