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Zs readings over limits
Former Community Member
Doing an EICR in a block of flats and quite a few of the lighting circuits have excessive Zs readings. All the circuits are on 60898 C10's without RCD protection with readings in the late 2 early 3 ohm range (max permitted 2.19). I know test result fails are generally a code 2 but these are LED panel downlighters with mostly class 2 drivers connected via choc boxes above the suspended ceiling so nothing really accessible. They would all comply with a C6 btw. Just wondered if you'd C2 this resulting in an unsatisfactory EICR
Hmm sounds like it has been marginal design right from the off. Anyone using more than one hundred metre reel on an installation really should check their loop impedances quite carefully.
A C10 might at the limit need 100A to instant trip, so your loop impedance should really be comfortably under 2.3 ohms with a suitable margin for low supply voltage (your 2,19 figure sound about right.).
I think you are looking at a C2, and the recommended fixes in order of ease and practicality will be either change to RCBO protection, derating to a lower current breaker or linking CPCs and or adding something to lower the R2.
Hmm sounds like it has been marginal design right from the off. Anyone using more than one hundred metre reel on an installation really should check their loop impedances quite carefully.
A C10 might at the limit need 100A to instant trip, so your loop impedance should really be comfortably under 2.3 ohms with a suitable margin for low supply voltage (your 2,19 figure sound about right.).
I think you are looking at a C2, and the recommended fixes in order of ease and practicality will be either change to RCBO protection, derating to a lower current breaker or linking CPCs and or adding something to lower the R2.
