Chrome Sockets and Switches

[TheFew]

Well I would have gotten away with 25m of cable! I guess my estimating skills are not too good

So the 50m of cable connected to the multimeter gave a reading at the meter at what seemed to be 1.2 to 1.3 Ohms.

I tested the earth at each light switch in turn and got readings ranging from 1.4 Ohms to 1.8 Ohms. The reading varied little depending on how much my hands were shaking. So I guess this means all of the earths wires are connected to the primary earth near the CU. Which is a start I guess...

I also tried testing the circuit between the chrome face plates and the CU earth. This showed as an open circuit, so there must be some limited insulation there!

So should I be happy that the risk of imminent shock death is now reduced?

Thanks

 

[ianniann]

I also tried testing the circuit between the chrome face plates and the CU earth. This showed as an open circuit, so there must be some limited insulation there!

So should I be happy that the risk of imminent shock death is now reduced?

Thanks

That doesn't really inspire confidence. Either the faceplates should be double-insulated or they should be connected to earth. I doubt that they're double-insulated. Normally there is a terminal for this clearly marked. On sockets, connecting the earth to the socket generally also connects the faceplate where necessary. Time to double-check the installation instructions again.

 

[TheFew]

That doesn't really inspire confidence. Either the faceplates should be double-insulated or they should be connected to earth. I doubt that they're double-insulated. Normally there is a terminal for this clearly marked. On sockets, connecting the earth to the socket generally also connects the faceplate where necessary. Time to double-check the installation instructions again.

The switches are these:

http://www.diy.com/departments/holder-10a-2-way-black-nickel-effect-switch/176843_BQ.prd

I had assumed that the "nickel effect" finish that is easily scratched with a screwdriver was not conductive. Unlike a more expensive solid brushed chrome switch. My assumption is probably flawed however!

 

[TheFew]

Just checked again. The touching the multimeter to the faceplate shows an open circuit.

Touching the multimeter to the screws that hold the faceplate in place show a path to earth and a low resistance reading (as the screws are earthing through the metal back box).

So the top finish on the switches is possibly not conductive? Otherwise the screws (at the very least) would give them a path to earth?

 

[SimonH2]

I'd suggest checking to the back of the faceplate where you can scratch the finish without causing cosmetic damage to the front. You'll probably find that shows continuity.

 

[ianniann]

It all depends if they are metal at all. If the faceplate and the switches themselves are plastic then there likely won't be a terminal for an earth wire (and take your chances on the screws being earthed to the back box!). The linked product says "black nickel effect" (should it be chrome effect?) and that doesn't sound to me like there is any metal involved. Real black nickel plate (generally on brass) is pretty tough - and conducts electricity

 

[TheFew]

Hi again,


This morning I put the probes of the multimeter across the surface of the faceplate (on the front and back) without scraping off the surface to get to the metal underneath. In both cases the multimeter registered an open circuit. So I would assume that the surface of the faceplate has been designed not to be conductive!


Looking at the earthing terminal again on the rear side of the switch, this is connected to a copper colored piece of metal that forms the crew holes in the face plate. Putting the meter across both screw holes shows that there is a circuit between them. So it seems that the screw holes are earthed, and is probably why the screws show as earthed.


Thanks

 

[SimonH2]

In that case, I think it's reasonable to assume that the manufacturer has considered things - anything that needs to be earthed should be connected to the earth terminal, if it's not then the manufacturer must consider it either DI (double insulated) or non-conductive. As long as the earth terminal is earthed, then you should be OK.
That's assuming a manufacturer who cares ! I know the likes of B&Q sell some horrible stuff, but AFAIK they don't knowingly sell "dodgy electrics" like some of the stuff you can easily get from certain online marketplaces.

 

[ianniann]

All sounds good. I'm always happier with switches that directly earth the screws, whatever the regulations might ay.

 

[TheFew]

Thanks for all the help people! Next week it is the Chrome sockets!

 

[ianniann]

Thanks for all the help people! Next week it is the Chrome sockets!

off-topic, but black nickel light switches and chrome sockets? You may be inspired or you may be mad ...

 

[TheFew]

off-topic, but black nickel light switches and chrome sockets? You may be inspired or you may be mad ...

Sorry I use "chrome" as a throw away term they are in fact Black Nickel as well!