R1+r2

snowplough · Sep 26, 2010

hI guys,
Wonder if any of you can clarify the reason why you test at furfest ceiling rose when doing the R1+R2 reading on a lighting circuit as no matter which way i look at it the switch opperating that ceiling rose covers the same distance so why cant you take the reading from that unless of course the line and earth both terminate in the last rose .

Im just starting level 3 so i appreciate your feed back.

snowplough

telectrix · Sep 26, 2010

usually lights are wired on loop-in. so your circuit is fron the CU to the last light permanent L/N/E. as that is the furthest point, that is where you measure R1+R2. the switch wire is irrevelant. if wired to switch first, the the switch has to be closede to measure L/E

Amp David · Sep 26, 2010

You should test at every point, not just the ceiling rose. Where you obtain your highest reading, should be the furthest point.

Amp David · Sep 26, 2010

Testing at a rose will also verify the switch line from switch to rose.

Sintra · Sep 26, 2010

R1 + R2 should be measured at all points on the circuit.

snowplough · Sep 26, 2010

Thanks for your replys guys although im still a little confused , i understand the highest reading should be noted as the R1+R2, and my tutor said it always at the last rose in a healthy circuit ai assume he means, but when i look at the length of wiring ,even though the line does finis in the last ceiling rose , if the earth finishe in the switch the surely the totall lenght of cable i.e R1+R2 is same in the last switch and rose that it feeds so surelly the readings should be the same in an healthy circuit ,so ou can take your R1+R2 from either.

Many thanks

snowplough