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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
Are the resistances you see compatible with the size of the building and likely wiring lengths ?
(each core of 1mm cross section is about 16 milliohms per metre long, so 3 ohms sounds like you have hundred meters or so of cable, perhaps 1600milliohms to get to the the fitting and the same again coming back )- sounds like rather a lot of wire if not and it is a small flat then there is a connection problem )
and what is the Zs at the board as it were ? (always possible the fault is really upstream, and was not there when it was put in, and now the bonding has come off or something.)
Something is not really right and a bit more info is needed.
Are the resistances you see compatible with the size of the building and likely wiring lengths ?
(each core of 1mm cross section is about 16 milliohms per metre long, so 3 ohms sounds like you have hundred meters or so of cable, perhaps 1600milliohms to get to the the fitting and the same again coming back )- sounds like rather a lot of wire if not and it is a small flat then there is a connection problem )
and what is the Zs at the board as it were ? (always possible the fault is really upstream, and was not there when it was put in, and now the bonding has come off or something.)
Something is not really right and a bit more info is needed.
