No Trip Zs at light switch

[ADS]

I use a 1552.If you just want to check there is earth continuity at switches, connect a wander to the MET and probe to the screw heads.

Max R1+R2 (or max Zs if you prefer) will always be at the light, not the switch.

I beg to differ - with a T & E installation, the higher reading will be at the switch, as the CSA of the CPC is smaller than that of the 'Line' conductor.

You may be losing the length of the 'run' of the 'switched live' to the light fitting, but you gain the same length in CPC, which is a higher resistance, so a higher Zs.

 

[Andy™]

no. it will be at the light. dont forget, your live has to go to the switch and then back to the rose.

 

[Sidewinder]

ADS, good point, however, this will depend on the exact physical layout of the wiring will it not?

 

[ADS]

Andy, the CPC at the light fitting carries on down to the switch and ends there

You may be losing the length of the 'run' of the 'switched live' to the light fitting, but you gain the same length in CPC, which is a higher resistance, so a higher Zs.

---------- Post Auto-Merged at 22:36 ---------- Previous post was made at 22:34 ----------

ADS, good point, however, this will depend on the exact physical layout of the wiring will it not?

That's true, Sidewinder.

It's only the case if there is just one light fitting being switched.

If there are multiple light fittings from one switch, and the switch is wired from the first one, then you'd have to go to the last light.

It also needs to be wired 'loop in' of course.

 

[Andy™]

good point.... so if its wired in 1.5/1mm then it will be at the switch. if its wired in 1/1mm then it should be the same at the light or the switch