Light switches

[rshort1987]

Hi
Not strictly an electrics question but I am wanting to change the light switches in my house. They are currently just the run-of-the-mill white plastic ones. However one of my double switches sticks out from the surface with a pattress (?) box. I am wanting to replace with metal light switches. What are my options here?
Thanks

 

[bubachuba]

Hi,
Nothing stopping you swapping them over to a metal finish as long as you have an earth on your lighting circuit. If you do, make sure you isolate the circuit first and take a photo of the existing connection and replace like for like to avoid any problems. This is assuming you are going to be doing it yourself of course?

 

[Taylortwocities]

Dig a hole in the wall and put in a metal back box.

There is no option. If you have metal light switches, they MUST be earthed. Do you have an earth connection to the light switches, is it actually connected to earth?>

 

[rshort1987]

This is why this site is great, this is not something I had thought about or knew was required. Although I haven't given much thought to the job yet, its all speculative at the moment.

Yes I will be doing this myself. How do I go about checking that they are earthed appropriately? I have just done a quick search and found some different threads on here that may be helpful. I will look over the weekend behind the switches. If there is any doubt/uncertainty is it better for an electrician to do the work or is there something a DIY-er can do?

Just out of interest are plastic switches ok then not to be earthed? what would be the dangers with unearthed metal switches?

Thanks

 

[bubachuba]

How do I go about checking that they are earthed appropriately?

A professional would use an earth fault loop impedance tester to confirm this. Although you would like to think if the earth cable is present - all is OK, unfortunately without testing it cannot be confirmed.

If there is any doubt/uncertainty is it better for an electrician to do the work or is there something a DIY-er can do?

It's a quick job to test and replace so if it doubt, yes.

Just out of interest are plastic switches ok then not to be earthed? what would be the dangers with unearthed metal switches?

Plastic switches do not require an earth connection because they do not conduct electricity like metal items do. The danger with unearthed metal switches in the event they became live due to a fault, there would be no path for it to flow to earth and operate the protective device which is what should happen in a working system.

 

[chivers67]

In simple terms if for whatever reason one of the face plates became live without an earth on it you effectively become a conductor when you touch it and could/will get an electric shock. If it's earthed and a live wire touches it then an MCB or other protective device should "blow".

 

[chivers67]

Buy some of this if you decide to change them all yourself > http://www.diy.com/departments/tower-green-yellow-single-core-cable-15mm-l5m/188999_BQ.prd . You can use this to join the back box and your switch plates without having to faff about with earth sleeving

 

[stillp]

How do I go about checking that they are earthed appropriately?

A multimeter on a low resistance range is as good as can be expected for a DIYer. You'll need a long lead to check for low resistance between the green/yellow wire that should be connected in your backboxes and your MET (Main Earth Terminal).

 

[JohnW2]

How do I go about checking that they are earthed appropriately?

A multimeter on a low resistance range is as good as can be expected for a DIYer.

Indeed - and, I would say, perfectly adequate for this purpose, if done properly. Don't forget that with the probable B6 MCB, one is only looking for a resistance less than about 7.28Ω to achieve required disconnection times (yet the actual resistance is likely to be far less than that), and that should be easily achievable with a multimeter. The only real difference from the meter that an electrician would probably use is that, when using a multimeter, one has to manually subtract the resistance of the 'long lead'.

Kind Regards, John

 

[PBC_1966]

I wonder why the manufacturers never seemed to get around to making double-insulated metal light switches?

 

[JohnW2]

I wonder why the manufacturers never seemed to get around to making double-insulated metal light switches?

IIRC, there are some.

Kind Regards, John

 

[PBC_1966]

Ah, fair enough - I just don't remember ever seeing any.

 

[EFLImpudence]

Don't forget that with the probable B6 MCB, one is only looking for a resistance less than about 7.28Ω to achieve required disconnection times (yet the actual resistance is likely to be far less than that),

Are you forgetting R1 and Ze ?

 

[bubachuba]

Don't forget that with the probable B6 MCB, one is only looking for a resistance less than about 7.28Ω to achieve required disconnection times (yet the actual resistance is likely to be far less than that),

Are you forgetting R1 and Ze ?

thats a valid point EFLI. ADS is based on the combined value after all.

 

[JohnW2]

Don't forget that with the probable B6 MCB, one is only looking for a resistance less than about 7.28Ω to achieve required disconnection times (yet the actual resistance is likely to be far less than that),

Are you forgetting R1 and Ze ?

Good point - I didn't think for long enough, but I think my point still stands. ....

... we're obviously only talking TN, so Ze will be relatively trivial, and hence the required maximum R2 will be no less than 3Ω - and I think that is easily within the scope of a properly utilised multimeter.

Kind Regards, John